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The International Authority on Air System Components AIR MOVEMENT AND CONTROL ASSOCIATION INTERNATIONAL, INC. AMCA Publication 203-90 Field Performance Measurement of Fan Systems (R2007)
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The International Authority on Air System Components

AIR MOVEMENT AND CONTROLASSOCIATION INTERNATIONAL, INC.

AMCAPublication 203-90

Field Performance Measurement of Fan Systems

(R2007)

AMCA PUBLICATION 203-90 (R2007)

Field Performance Measurement

of Fan Systems

Air Movement and Control Association International, Inc.

30 West University Drive

Arlington Heights, IL 60004-1893

© 2007 by Air Movement and Control Association International, Inc.

All rights reserved. Reproduction or translation of any part of this work beyond that permitted by Sections 107 and

108 of the United States Copyright Act without the permission of the copyright owner is unlawful. Requests for

permission or further information should be addressed to the Executive Director, Air Movement and Control

Association International, Inc. at 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.

Forward

The original edition of Publication 203 was released in 1976. This, the second edition, updates much of theinformation that was presented.

Annex K (estimating the power output of three phase motors) and Annex L (estimating belt drive losses) wererewritten and adjusted based on new information received from motor and drive manufacturers. Over four hundredbelt drive loss tests were analyzed.

New axial fan System Effect Factors were established based on a test project conducted and underwritten byAMCA. These factors were incorporated in their respective, applicable field test examples shown in Annex A.

The intent of this publication is to provide information from which test procedures can be developed to meet theconditions and requirements encountered in specific field test situations. They include the proper procedure fordetermining various System Effect Factors. Numerous examples of actual field tests are presented in detail inAnnex A. These examples provide sufficient guidance for the proper field testing of most fan system installations.

Authority

AMCA Publication 203 was approved by the Air Movement Control Association Membership in 1990. It wasreaffirmed July, 2007.

AMCA 203 Review Committee

Robert H. Zaleski, Chairman Acme Engineering & Manufacturing Corp.

Narsaiah Dasa TLT-Babcock, Inc.

James L. Smith Aerovent, Inc.

Jack E. Saunders Barry Blower/SnyderGeneral Corp.

Erling Schmidt Novenco, Inc.

Gerald P. Jolette AMCA Staff

Disclaimer

AMCA uses its best efforts to produce standards for the benefit of the industry and the public in light of availableinformation and accepted industry practices. However, AMCA does not guarantee, certify or assure the safety orperformance of any products, components or systems tested, designed, installed or operated in accordance withAMCA standards or that any tests conducted under its standards will be non-hazardous or free from risk.

Objections to AMCA Standards and Certifications Programs

Air Movement and Control Association International, Inc. will consider and decide all written complaints regardingits standards, certification programs, or interpretations thereof. For information on procedures for submitting andhandling complaints, write to:

Air Movement and Control Association International30 West University DriveArlington Heights, IL 60004-1893 U.S.A.

or

AMCA International, Incorporatedc/o Federation of Environmental Trade Associations2 Waltham Court, Milley Lane, Hare HatchReading, BerkshireRG10 9TH United Kingdom

Related AMCA Standards and Publications

Publication 200 AIR SYSTEMS

System Pressure Losses

Fan Performance Characteristics

System Effect

System Design Tolerances

Air Systems is intended to provide basic information needed to design effective and energy efficient air systems.

Discussion is limited to systems where there is a clear separation of the fan inlet and outlet and does not cover

applications in which fans are used only to circulate air in an open space.

Publication 201 FANS AND SYSTEMS

Fan Testing and Rating

The Fan "Laws"

Air Systems

Fan and System Interaction

System Effect Factors

Fans and Systems is aimed primarily at the designer of the air moving system and discusses the effect on inlet and

outlet connections of the fan's performance. System Effect Factors, which must be included in the basic design

calculations, are listed for various configurations. AMCA 201-02 and AMCA 203-90 are companion documents.

Publication 202 TROUBLESHOOTING

System Checklist

Fan Manufacturer's Analysis

Master Troubleshooting Appendices

Troubleshooting is intended to help identify and correct problems with the performance and operation of the air

moving system after installation.

Publication 203 FIELD PERFORMANCE MEASUREMENTS OF FAN SYSTEMS

Acceptance Tests

Test Methods and Instruments

Precautions

Limitations and Expected Accuracies

Calculations

Field Performance Measurements of Fan Systems reviews the various problems of making field measurements

and calculating the actual performance of the fan and system. AMCA 203-90 and AMCA 201-02 are companion

documents.

TABLE OF CONTENTS

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

3, Types of Field Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

4. Alternatives to Conducting Field Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

5. System Effect Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

6. Fan Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

7. Referenced Planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

8. Symbols and Subscripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

9. Fan Flow Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

9.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

9.2 Velocity measuring instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

9.3 Location of traverse plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

9.4 The traverse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

9.5 Flow rate calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

9.6 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

10. Static Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

10.2 Pressure measuring instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

10.3 Static pressure measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

10.4 Static pressure calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

10.5 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

11. Fan Power Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

11.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

11.2 Power measurement methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

11.3 Power measuring instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

11.4 Power transmission losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

11.5 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

12. Fan Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

12.1 Speed measuring instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

12.2 Speed measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

13. Densities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

13.1 Locations of density determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

13.2 Data required at each location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

13.3 Additional data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

13.4 Density values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

13.5 Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

13.6 Barometric pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

13.7 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

14. Conversion Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

15. Test Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

16. Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

17. Typical Fan-System Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

17.1 Free inlet, free outlet fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

17.2 Free inlet, ducted outlet fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

17.3 Ducted inlet, ducted outlet fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

17.4 Ducted inlet, free outlet fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

17.5 Air handling units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Annex A Field Test Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Annex B Pitot-Static Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97

Annex C Double Reverse Tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98

Annex D Pitot-Static Tube Holder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99

Annex E Static Pressure Tap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100

Annex F Pitot-Static Tube Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101

Annex G Manometer Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102

Annex H Distribution of Traverse Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104

Annex J Instrumentation Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106

Annex K Phase Current Method for Estimating the Power Output of

Three Phase Fan Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108

Annex L Estimated Belt Drive Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110

Annex M Density Determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112

Annex N Density Charts and Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117

Annex P Diffusion at Fan Outlets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125

Annex R Diffusion at Fan Outlets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126

Annex S Typical Format for Field Test Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130

Annex T Uncertainties Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131

1

Field Performance

Measurement of Fan Systems

1. Introduction

Performance ratings of fans are developed from

laboratory tests made according to specified

procedures on standardized test setups. In North

America, the standard is ANSI/AMCA Standard 210 /

ANSI/ASHRAE 51 Laboratory Methods of TestingFans for Rating.

In actual systems in the field, very few fans are

installed in conditions reproducing those specified in

the laboratory standard. This means that, in

assessing the performance of the installed fan-

system, consideration must be given to the effect on

the fan’s performance of the system connections,

including elbows, obstructions in the path of the

airflow, sudden changes of area, etc. The effects of

system conditions on fan performance is discussed in

Section 5, and more completely in AMCA Publication

201, Fans and Systems.

A major problem of testing in the field is the difficulty

of finding suitable locations for making accurate

measurements of flow rate and pressure. Sections

9.3 and 10.3 outline the requirements of suitable

measurement sections.

Because these problems and others will require

special consideration on each installation, it is not

practical to write one standard procedure for the

measurement of the performance of all fan-systems

in the field. This publication offers guidelines to

making performance measurements in the field

which are practical and flexible enough to be applied

to a wide range of fan and system combinations.

Because of the wide variety of fan types and systems

encountered in the field, Annex A includes examples

of a number of different field tests. In most cases,

these examples are based on actual tests which have

been conducted in the field.

Before performing any field test, it is strongly

recommended that the following AMCA publications

be carefully reviewed:

AMCA Publication 200 - Air SystemsAMCA Publication 201 - Fans and SystemsAMCA Publication 202 - TroubleshootingAMCA Standard 210 - Laboratory Methods of Testing

Fans for Rating

2. Scope

The recommendations and examples in this

publication may be applied to all types of centrifugal,

axial, and mixed flow fans in ducted or nonducted

installations used for heating, ventilating, air

conditioning, mechanical draft, industrial process,

exhaust, conveying, drying, air cleaning, dust

collection, etc. Although the word air is used when

reference is made in the general sense to the

medium being handled by the fan, gases other than

air are included in the scope of this publication.

Measurement of sound, vibration, and stress levels

are not within the scope of this publication.

3. Types of Field Tests

There are three general categories of field tests:

A) General Fan System Evaluation - A

measurement of the fan-system’s performance to

use as the basis of modification or adjustment of

the system.

B) Acceptance Test - A test specified in the sales

agreement to verify that the fan is achieving the

specified performance.

C) Proof of Performance Test - A test in response

to a complaint to demonstrate that the fan is

meeting the specified performance requirement.

As acceptance and proof of performance tests are

related to contract provisions, they are usually

subject to more stringent requirements and are

usually more costly than a general evaluation test. In

the case of large fans used in industrial applications

and of mechanical draft fans used in the electrical

power generation industry the performance of a field

test may be part of the purchase agreement between

the fan manufacturer and the customer. In addition to

Publication 203, AMCA Standard 803 SitePerformance Test Standard-Power Plant andIndustrial Fans defines the conditions which must be

met to achieve higher accuracy of measurement. In

new installations of this type, it is desirable to include

a suitable measuring section in the design.

Agreement must be reached on the test method to be

used prior to performance of the test.

AMCA INTERNATIONAL, INC. AMCA 203-90 (R2007)

2

4. Alternatives to Field Tests

In some cases, considerations such as cost and

problems of making accurate measurements may

make the following alternative methods of testing

worth investigation:

A) Testing the fan before installation in a laboratory

equipped to perform tests in accordance with

AMCA Standard 210. Limitations in laboratory

test facilities may preclude tests on full size fans.

In this case, the full size fan can be tested at the

installation site in accordance with AMCA

Standard 210. This will usually require the

installation of special ductwork.

B) Testing a reduced scale model of the fan in

accordance with AMCA Standard 210 and

determining the performance of the full size fan

as described in AMCA Publication 802, PowerPlant Fans – Establishing Performance UsingLaboratory Methods.

C) Testing a reduced scale model of the complete

fan and system using the test methods outlined

in this publication.

Tests conducted in accordance with AMCA Standard

210 will verify the performance characteristics of the

fan but will not take into account the effect of the

system connections on the fan’s performance (see

Section 5).

5. System Effect Factors

AMCA Publication 201, Fans and Systems, deals in

detail with the effect of system connections on fan

performance. It gives system effect factors for a wide

variety of obstructions and configurations which may

affect a fan’s performance.

System Effect Factor (SEF) is a pressure loss which

recognizes the effect of fan inlet restrictions, fan

outlet restrictions, or other conditions influencing fan

performance when installed in the system.

SYSTEM EFFECT FACTORS (SEFs) AREINTENDED TO BE USED IN CONJUNCTION WITHTHE SYSTEM RESISTANCE CHARACTERISTICSIN THE FAN SELECTION PROCESS. Where SEFs

are not applied in the fan selection process, SEFs

must be applied in the calculations of the results of

field tests. This is done for the purpose of allowing

direct comparison of the test results to the design

static pressure calculation. Thus, for a field test, the

fan static pressure is defined as:

Ps = Ps2 - Ps1 – Pv1 + SEF 1 + SEF 2 + …+ SEF n

Examples of the application of SEFs in determining

the results of field tests are included in Annex A.

In field tests of fan-system installations in which

system effects have not been accounted for, it is

important that their sources be recognized and their

magnitudes be established prior to testing.

The alternative to dealing with a large magnitude

SEF is to eliminate its source. This requires revisions

to the system. This alternative course of action is

recommended when swirl exists at the fan inlet (see

Publication 201, Figure 9.8). The effect on fan

performance as a result of swirl at the inlet is

impossible to estimate accurately as the system

effect is dependent upon the degree of swirl. The

effect can range from a minor amount to an amount

that results in the fan-system performance being

completely unacceptable.

6. Fan Performance

Fan performance is a statement of fan flow rate, fan

total or static pressures, and fan power input at stated

fan speed and fan air density. Fan total or static

efficiencies may be included. The fan air density is

the density at the fan inlet. The fan flow rate is the

volume flow rate at the fan inlet density.

7. Referenced Planes

Certain locations within a fan-system installation are

significant to field tests. These locations are

designated as follows:

Plane 1: Plane of fan inlet

Plane 2: Plane of fan outlet

Plane 3: Plane of Pitot-static tube traverse for

purposes of determining flow rate

Plane 4: Plane of static pressure measurement

upstream of fan

Plane 5: Plane of static pressure measurement

downstream of fan

The use of the numerical designations as subscripts

indicate that the values pertain to those locations.

AMCA 203-90 (R2007)

3

8. Symbols and Subscripts

SYMBOL DESCRIPTION UNIT

A Area of cross-section ft2

D Diameter ft

De Equivalent diameter ft

FLA Full load amps amps

H Fan power input hp

HL Power transmission loss hp

Hmo Motor power output hp

kW Electrical power kilowatts

L Length ft

N Speed of rotation rpm

NLA No load amps amps

NPH Nameplated horsepower hp

NPV Nameplated volts volts

Ps Fan static pressure in. wg

Psx Static pressure at Plane x in. wg

Pt Fan total pressure in. wg

Ptx Total pressure at Plane x in. wg

Pv Fan velocity pressure in. wg

Pvx Velocity pressure at Plane x in. wg

pb Barometric pressure in. Hg

pe Saturated vapor pressure at tw in. Hg

pp Partial vapor pressure in. Hg

px Absolute pressure at Plane x in. Hg

Q Fan flow rate cfm

Qi Interpolated flow rate cfm

Qx Flow rate at Plane x cfm

SEF System effect factor in. wg

T Torque lb-in.

td Dry-bulb temperature °F

tw Wet-bulb temperature °F

V Velocity fpm

ΔPx,x’ Pressure loss between

Planes x and x’ in. wg

ΔPs Pressure loss across damper in. wg

ρ Fan gas density lbm/ft3

ρx Gas density at Plane x lbm/ft3

Σ Summation sign ---

Airflow direction ---

SUBSCRIPT DESCRIPTION

c Value converted to specified conditions

r Reading

x Plane 1, 2, 3, ..., as appropriate

1 Plane 1 (fan inlet)

2 Plane 2 (fan outlet)

3 Plane 3 (plane of Pitot-static traverse for

purpose of determining flow rate

4 Plane 4 (plane of static pressure

measurement upstream of fan)

5 Plane 5 (plane of static pressure

measurement downstream of fan)

9. Fan Flow Rate

9.1 General

Determine fan flow rate using the area, velocity

pressure, and density at the traverse plane and the

density at the fan inlet. The velocity pressure at the

traverse plane is the root mean square of the velocity

pressure measurements made in a traverse of the

plane. The flow rate at the traverse plane is

calculated by converting the velocity pressure to its

equivalent velocity and multiplying by the area of the

traverse plane.

9.2 Velocity measuring instruments

Use a Pitot-static tube of the proportions shown in

Annex B or a double reverse tube, shown in Annex C,

and an inclined manometer to measure velocity

pressure. The velocity pressure at a point in a gas

stream is numerically equal to the total pressure

diminished by the static pressure. The Pitot-static

tube is connected to the inclined manometer as

shown in Annex F. The double reverse tube is

connected to the inclined manometer as shown in

Annex C.

9.2.1 Pitot-static tube. The Pitot-static tube is

considered to be a primary instrument and need not

be calibrated if maintained in the specified condition.

It is suited for use in relatively clean gases. It may be

used in gases that contain moderate levels of

particulate matter such as dust, water, or dirt,

provided certain precautions are employed (see

Section 15).

9.2.2 Double reverse tube. The double reverse tube

is used when the amount of particulate matter in the

gas stream impairs the function of the Pitot-static

tube. The double reverse tube requires calibration. It

is important that the double reverse tube be used in

the same orientation as used during calibration. Mark

the double reverse tube to indicate the direction of

the gas flow used in its calibration.

9.2.3 Inclined manometers. Inclined manometers

are available in both fixed and adjustable range

types. Both types require calibration. The adjustable

range type is convenient in that it may be adjusted at

the test site to the range appropriate to the velocity

pressures which are to be measured. It is adjusted by

changing the slope to any of the various fixed

settings and by changing the range scale

accordingly. Each setting provides a different ratio of

the length of the indicating column to its indicated

height. Adjustable range type manometers in which

the slope may be fixed at 1:1, 20:1, and intermediate

ratios are available (see Figure 10 in Annex G).

AMCA 203-90 (R2007)

4

The accuracy of the manometer used in the

measurement of velocity pressures is of prime

importance. Select a manometer that will provide an

acceptable degree of accuracy; consider the range,

slope, quality, scale graduations, indicating fluid of

the instrument and the range of the velocity

pressures to be measured. The graph in Annex G

indicates the effect of expected resolution of

manometer readings on the accuracy of velocity

determinations. The basis for this graph is described

in Section 9.6. Determine velocities in the very low

range more accurately by using a manometer with a

slope of 20:1. Due to practical limitations in length, its

use is restricted to measurements where the

velocities are very low. Also, errors in velocity

determinations made by using a Pitot-static tube and

manometer exceed normally acceptable values at

velocity pressure readings less than 0.023 in. wg.

This corresponds to a velocity of approximately 600

fpm for air of 0.075 lbm/ft3 density.

9.2.4 Low velocity instruments. Normally, velocities

encountered in the field test situations are well in

excess of 600 fpm. Therefore, recommendations

regarding alternate test procedures and

instrumentation for use for velocities less than 600

fpm are not presented in this publication.

Descriptions of various types of instruments used to

determine range velocities are presented in Annex J.

Most of the instruments require frequent calibration,

and some are not suited for use in high temperature,

dirty, wet, corrosive, or explosive atmospheres. If it is

necessary to use one of these instruments, the

procedure for its use, its calibration, and the expected

accuracy of results should be agreed upon by all

interested parties.

9.3 Location of traverse plane

For field tests, suitable test measurement station

locations must be provided in the system. When

suitable locations are not available, consider making

temporary or permanent alterations to the ducting for

improved test accuracy.

For free inlet, free outlet fans, convert a free inlet,

free outlet fan to a ducted inlet, free outlet fan by the

addition of a temporary duct. Estimate free inlet, free

outlet fan flow rate by measuring other parameters

and interpreting certified ratings performance (see

Section 17.1).

A Pitot traverse plane suitable for the measurements

used to determine flow rate are as follows:

1) The velocity distribution should be uniform

throughout the traverse plane. The uniformity of

distribution is considered acceptable when more

than 75% of the velocity pressure measurements

are greater than 1/10 of the maximum

measurement (see Figure 9.1)

2) The flow streams should be at right angles to the

traverse plane. Variations from this flow condition

as a result of swirl or other mass turbulence are

considered acceptable when the angle between

the flow stream and the traverse plane is within

10 degrees of a right angle. The angle of the flow

stream in any specific location is indicated by the

orientation of the nose of the Pitot-static tube that

produces the maximum velocity pressure reading

at the location.

3) The cross-sectional shape of the airway in which

the traverse plane is located should not be

irregular. Proper distribution of traverse points

and accurate determination of the area of the

traverse plane are difficult to achieve when the

airway does not conform closely to a regular

shape.

4) The cross-sectional shape and area of the airway

should be uniform throughout the length of the

airway in the vicinity of the traverse plane. When

the divergence or convergence of the airway is

irregular or more than moderate in degree,

significantly nonuniform flow conditions may

exist.

5) The traverse plane should be located to minimize

the effects of gas leaks between the traverse

plane and the fan.

6) When it is necessary to locate the traverse plane

in a converging or diverging airway (not

recommended), note that the traverse plane and

area is located at the tip of the Pitot-static tube.

A location well downstream in a long, straight run of

uniform cross-section duct will usually provide

acceptable conditions for the Pitot traverse plane.

When locating the traverse plane close to the fan, as

is often done in order to minimize the effect of

leakage, flow conditions upstream of the fan are

usually more suitable. In some installations, more

than one traverse plane may be required in order to

account for the total flow (Annex A contains

examples).

When a field test is anticipated, particularly when the

requirement for a field test is an item in the

specifications, the system designer should provide a

suitable traverse plane location in the system.

When the fan is ducted outlet and the traverse plane

is to be located downstream from the fan, the

AMCA 203-90 (R2007)

5

AMCA 203-90 (R2007)

Pv MAX Pv MAX

Pv MAX

Pv MAX

Pv MAX

A: IDEAL Pv DISTRIBUTION B: GOOD Pv DISTRIBUTION (ALSO SATISFACTORY FOR FLOW INTO FAN INLETS. MAY BE UNSATISFACTORY FOR FLOW INTO INLET BOXES - MAY PRODUCE SWIRL IN BOXES)

C: SATISFACTORY Pv DISTRIBUTION - MORE THAN 75% OF Pv READINGS GREATER THAN:

D: DO NOT USE UNSATISFACTORY Pv DISTRIBUTION -

(UNSATISFACTORY FOR FLOW INTO FAN INLETS OR INLET BOXES)

(UNSATISFACTORY FOR FLOW INTO FAN INLETS OR INLET BOXES)

(UNSATISFACTORY FOR FLOW INTO FAN INLETS OR INLET BOXES)

LESS THAN 75% OF Pv READINGS GREATER THAN:

F: DO NOT USE UNSATISFACTORY Pv DISTRIBUTION LESS THAN 75% OF Pv READINGS GREATER THAN:

Pv MAX

10Pv MAX

10Pv MAX

10Pv MAX

10Pv MAX

10Pv MAX

10Pv MAX

(UNSATISFACTORY FOR FLOW INTO FAN INLETS OR INLET BOXES)

E: DO NOT USE UNSATISFACTORY Pv DISTRIBUTION LESS THAN 75% OF Pv READINGS GREATER THAN:

10Pv MAX

10Pv MAX

10Pv MAX

10Pv MAX

80%60%

35%40%

20% 35%

Figure 9.1 - Typical Velocity Pressure Distributions Encountered in Velocity

Pressure Measurement Planes in Fan-System Installations

6

AMCA 203-90 (R2007)

Z

MEASUREMENT PLANE

Y

INLET BOX DAMPERS

12 in. MIN.

WHERE: D YZe =

De2

MIN.

Note: The measurement plane should be located a minimum of ½ De from the inlet cone, but not less than 12 in.

from the leaving edge of the damper blades.

Figure 9.2

STACK

VELOCITYPROFILE

Note: Spiral vortex may form when fan discharges directly into a stack or similar arrangement.

Figure 9.3

7

traverse plane should be situated a sufficient

distance downstream from the fan to allow the flow to

diffuse to a more uniform velocity distribution and to

allow the conversion of velocity pressure to static

pressure. Annex P provides guidance for the location

of the traverse plane in these cases. The location of

the traverse plane on the inlet side of the fan should

not be less than ½ equivalent diameter from the fan

inlet. Regions immediately downstream from elbows,

obstructions and abrupt changes in airway area are

not suitable traverse plane locations. Regions where

unacceptable levels of swirl are usually present, such

as the region downstream from an axial flow fan that

is not equipped with straightening vanes, should be

avoided. Swirl may form when a fan discharges

directly into a stack or similar arrangement (see

Figure 9.2).

9.3.1 Inlet box location. When the traverse plane

must be located within an inlet box, the plane should

be located a minimum of 12 inches downstream from

the leaving edges of the damper blades and not less

than ½ equivalent diameter upstream from the edge

of the inlet cone (see Figure 9.3). Do not locate

traverse points in the wake of individual damper

blades. In the case of double inlet fans, traverses

must be conducted in both inlet boxes in order to

determine the total flow rate.

9.3.2 Alternative locations. On occasion, an

undesirable traverse plane location is unavoidable, or

each of a limited number of prospective locations

lacks one or more desirable qualities. In such cases,

the alternatives are:

1) Accept the most suitable location and evaluate

the effects of the undesirable aspects of the

location on the accuracy of the test results. In

some instances, the estimated accuracy may

indicate that the results of the test would be

meaningless, particularly in acceptance tests and

proof of performance tests.

2) Provide a suitable location by modifying the

system. This course of action is recommended

for acceptance tests and proof of performance

tests. The modifications may be temporary,

permanent, minor or extensive, depending on the

specific conditions encountered. When the inlet

side of the fan is not ducted but is designed to

accept a duct, consider installing a short length of

inlet duct to provide a suitable traverse plane

location. This duct should be of a size and shape

to fit the fan inlet, a minimum of 2 equivalent

diameters long and equipped with a bell shaped

or flared fitting at its inlet. The traverse plane

should be located a minimum of ½ equivalent

diameters from the fan inlet and not less than 1½

equivalent diameters from the inlet of the duct.

Where the duct is small, its length may

necessarily be greater than 2 equivalent

diameters in order to ensure that the tip of the

Pitot-static tube is a minimum of 1½ equivalent

diameters from the duct inlet. This short length of

duct should produce no significant addition to the

system resistance, but in some cases it may alter

the pattern of flow into the fan impeller, and

thereby affect the performance of the fan slightly.

9.4 The traverse

Annex H contains recommendations for the number

and distribution of measurement points in the

traverse plane. If the flow conditions at the traverse

plane are less than satisfactory, increase the number

of measurement points in the traverse to improve

accuracy.

Since the flow at a traverse plane is never strictly

steady, the velocity pressure measurements

indicated by the manometer will fluctuate. Each

velocity pressure measurement should be mentally

averaged on a time-weighted basis. Any velocity

pressure measurement that appears as a negative

reading is to be considered a velocity pressure

measurement of zero and included as such in the

calculation of the average velocity pressure.

When it is necessary to locate the traverse plane in a

converging or diverging airway, orient the nose of the

Pitot-static tube such that it coincides with the

anticipated line of the flow stream. This is particularly

important at measurement points near the walls of

the airway (see Annex A-1A).

No appreciable effect on Pitot-static tube readings

occur until the angle of misalignment between the

airflow and the tube exceeds 10 degrees.

9.5 Flow rate calculations

9.5.1 Flow rate at traverse plane. The flow rate at

the traverse plane is calculated as follows:

Q3 = V3A3

Where:

A3 = the area of the traverse plane

V3 = the average velocity at the traverse plane

= 1096 (Pv3/ρ3)0.5

ρ3 = the density at the traverse plane

Pv3 = the root mean square velocity pressure at the

traverse plane

= [∑(Pv3r)0.5 / number of readings]2

AMCA 203-90 (R2007)

8

Pv3r is the velocity pressure reading, corrected for

manometer calibration and where applicable,

corrected for the calibration of the double reverse

tube. It is important that the calibration of the double

reverse tube be applied correctly. The use of the

calibration of the double reverse tube is described in

Annex C.

9.5.2 Continuity of mass. The calculations of fan

flow rate are based on considerations of continuity of

mass, and as such, it is assumed that no mass is

added or removed from the gas stream between the

traverse plane and the fan inlet. In the general

application, having determined the flow rate and

density at the traverse plane, the flow rate at any

location, (x), in the fan-system installation may be

calculated, providing the density at this location is

known and the assumption noted above is valid, i.e.:

Qx = Q3 (ρ3/ρx)

9.5.3 Fan flow rate, single traverse plane. Where a

single traverse plane is used, the calculation of the

fan flow rate is:

Q = Q1

= Q3 (ρ3/ρ1)

Where:

Q3 and ρ3 = as described in Section 9.5.1

ρ1 = the density at the fan inlet

9.5.4 Fan flow rate, multiple traverse planes.

When it is necessary to use more than one traverse

plane in order to account for the total flow:

Q = Q1

= Q3a (ρ3a/ρ1) + Q3b (ρ3b/ρ1) + ... + Q3n (ρ3n/ρ1)

9.6 Accuracy

The performance item of major concern in most fan-

system installations is the flow rate. Every effort

should be made to improve the accuracy of the flow

rate determination. The uncertainty analysis

presented in Annex T indicates that the uncertainties

in flow rate determinations will range from 2% to

10%. This range is based on considerations of the

conditions that are encountered in most field test

situations. This includes instances in which the

conditions at the Pitot traverse plane do not conform

to all of the qualifications indicated in Section 9.3.

The graph in Annex G provides guidance for

improving the accuracy of the flow rate

determinations. This graph indicates the effect of

expected resolution of velocity determinations. This

effect is shown for several manometer slope ratios.

For all ratios, the expected resolution used as a basis

for the graph is the length of indicating column

equivalent to 0.05 in. wg in a manometer with slope

ratio of 1:1. As indicated in the graph, reading

resolution uncertainty can be significant. However,

this uncertainty can be controlled by selecting a

manometer with a slope suited to the velocity

pressures to be measured and by avoiding regions of

very low velocity in the selection of the traverse plane

location. Reading resolution uncertainties exceed

normally acceptable values at velocity pressures less

than 0.023 in. wg. This corresponds to a velocity of

approximately 600 fpm for air of 0.075 lbm/ft3 density.

Generally, ducts are sized for velocities considerably

in excess of 600 fpm. Velocities less than 600 fpm

may exist in certain sections of the system in some

installations, but these sections can usually be

avoided. Do no use a Pitot-static tube and

manometer to determine velocities in the low ranges

associated with filters and cooling coils in air

conditioning, heating, and ventilating units. In some

instances, the uncertainties incurred in the

determinations of low velocity flows may be

acceptable. For example, an uncertainty of 15% in

the determination of the flow rate in a branch duct

that accounts for 20% of the total flow rate for the

system affects the accuracy of the total flow rate

determination by only 3%.

In addition to low range velocities, other conditions

may exist at the traverse plane which can

significantly affect the accuracy of the flow rate

determination. These include nonuniform velocity

distribution, swirl, and other mass turbulence.

Improve the accuracy of the flow rate determination

by avoiding these conditions in the selection of the

traverse plane location, or improve the conditions by

modifying the system.

10. Fan Static Pressure

10.1 General

Determine fan static pressure by using the static

pressures at the fan inlet and outlet, the velocity

pressure at the fan inlet, and applicable SystemEffect Factors. The use of System Effect Factors in

the determination of fan static pressure is described

in Section 5. The velocity pressure at the fan inlet is

the calculated average velocity pressure at this

location, and as such, its determination is based on

the fan flow rate, the density at the fan inlet, and the

fan inlet area. The static pressures at the fan inlet and

outlet may be obtained directly by making pressure

measurements at these locations; or they may be

AMCA 203-90 (R2007)

9

determined by making pressure measurements at

other locations, upstream and downstream of the fan.

In the latter case, the determinations must account

for the effects of velocity pressure conversions and

pressure losses, as may occur between the

measurement planes and the planes of interest.

10.2 Pressure measuring instruments

This section describes only the instruments for use in

measuring static pressure. Instruments for use in the

other measurements involved in the determination of

fan static pressure are described in Section 13.

Use a Pitot-static tube of the proportions shown in

Annex B, a double reverse tube as shown in Annex

C, or a side wall pressure tap as shown in Annex E,

and a manometer to measure static pressure.

10.2.1 Pitot-static tube. The comments that appear

in Section 9.2 regarding the use and calibration of the

Pitot-static tube are applicable to its use in the

measurement of static pressures.

10.2.2 Double reverse tube. The double reverse

tube cannot be used to measure static pressure

directly. It must be connected to two manometers and

the static pressure for each point of measurement

must be calculated. Both the manometer connections

and the method of calculation are shown in Annex C.

10.2.3 Pressure tap. The pressure tap does not

require calibration. Use no fewer than four taps

located 90 degrees apart. In rectangular ducts, a

pressure tap should be installed near the center of

each wall. It is important that the inner surfaces of the

duct in the vicinities of the pressure taps be smooth

and free from irregularities, and that the velocity of

the gas stream does not influence the pressure

measurements.

10.2.4 Manometers. A manometer with either

vertical or inclined indicating column may be used to

measure static pressure. Inclined manometers used

to measure static pressures require calibration and

should be selected for the quality, range, slope, scale

graduations, and indicating fluid necessary to

minimize reading resolution errors.

10.3 Static pressure measurements

It is important that all static pressure measurements

be referred to the same atmospheric pressure, and

this atmospheric pressure be that for which the

barometric pressure is determined.

Make static pressure measurements near the fan

inlet and the fan outlet, and where the airway

between the measurement plane and the plane of

interest is straight and without change in cross-

sectional area. Then the duct friction loss between

the measurement plane and the plane of interest is

usually insignificant, and considerations of velocity

pressure conversions and calculations of pressure

losses for duct fitting and other system components

can be avoided.

When a system component is situated between the

measurement plane and the plane of interest, the

pressure loss of the component must be calculated

and credited to the fan. The calculation of the

pressure loss is usually based on the component’s

performance ratings, which may be obtained from the

manufacturer of the item.

If there is a change in area between the

measurement plane and the plane of interest, then

the calculation of the static pressure at the plane of

interest must account for velocity pressure

conversion and include any associated pressure

loss. When the change in area is moderate and

gradual, the conversion of velocity pressure is

considered to occur without loss and the static

pressure is calculated on the basis of no change in

total pressure between the measurement plane and

the plane of interest. This assumes that the duct

friction loss between the two planes is negligible.

When the change in area is an abrupt and sizable

enlargement, as in a duct leading into a large

plenum, the loss is considered to be equivalent to the

velocity pressure in the smaller area, and the static

pressure at the plane of interest is considered to be

the same as the static pressure at the measurement

plane. This assumes that the velocity pressure in the

larger area and the duct friction loss are negligible.

10.3.1 Location of the measuring plane. When the

fan is ducted outlet, the static pressure measurement

plane downstream of the fan should be situated a

sufficient distance from the fan outlet to allow the flow

to diffuse to a more uniform velocity distribution and

to allow the conversion of velocity pressure to static

pressure. See Annex P for guidance in locating the

measurement plane in these cases. In general,

pressure taps should be used if it is necessary to

measure static pressure in the immediate vicinity of

the fan outlet. The static pressure at this location is

difficult to measure accurately with a Pitot-static tube

due to the existence of turbulence and localized high

velocities. If the surface conditions or the velocities at

the duct walls are unsuited for the use of pressure

taps, then a Pitot-static tube must be used with

extreme care, particularly in aligning the nose of the

tube with the lines of the flow streams.

The location of the static pressure measurement

AMCA 203-90 (R2007)

10

plane upstream of the fan should not be less than ½

equivalent diameter from the fan inlet. In the event

that static pressure measurements must be made in

an inlet box, the measurement plane should be

located as indicated in Figure 9.2. In the case of

double inlet fans, static pressure measurements must

be made in both inlet boxes in order to determine the

average static pressure on the inlet side of the fan.

In general, the qualifications for a plane well suited

for the measurement of static pressure are the same

as those for the measurement of velocity pressure,

as indicated in Section 9.3:

1) The velocity distribution should be uniform

throughout the traverse plane.

2) The flow streams should be at right angles to the

plane.

3) The cross-sectional shape of the airway in which

the plane is located should not be irregular.

4) The cross-sectional shape and area of the airway

should be uniform throughout the length of the

airway in the vicinity of the plane.

5) The plane should be located such as to minimize

the effects of leaks in the portion of the system

that is located between the plane and the fan.

A long, straight run of duct upstream of the

measurement plane will usually provide acceptable

conditions at the plane. Regions immediately

downstream from elbows, obstructions, and abrupt

changes in airway area are generally unsuitable

locations. Regions where unacceptable levels of

turbulence are present should be avoided.

If in any fan-system installation the prospective

locations for static pressure measurement planes

lack one or more desirable qualities, the alternatives

are to accept the best qualified locations and

evaluate the effects of the undesirable aspects of the

conditions on the accuracy of the test results or

provide suitable locations by modifying the system.

10.3.2 When using a Pitot-static tube or a double

reverse tube to measure static pressure, a number of

measurements must be made throughout the plane.

Use Annex H to determine the number and

distribution of the measurement points. When using

pressure taps, a single measurement at each of the

taps located at the plane is sufficient.

10.4 Static pressure calculations

Static pressure measurements may be positive or

negative. By definition, positive values are those

measured as being greater than atmospheric

pressures; negative values are those measured as

being less than atmospheric pressure. In all of the

equations in this publication, the values of static

pressures must be entered with their proper signs

and combined algebraically.

10.4.1 Static pressure at measuring planes. The

static pressure at a plane of measurement (x) is

calculated as follows:

Where:

Psxr = the static pressure reading, corrected for

manometer calibration

10.4.2 Static pressure at fan inlet or outlet. The

static pressure at the fan inlet, Ps1, and the static

pressure at the fan outlet, Ps2, may be measured

directly in some cases. In most cases, the static

pressure measurements for use in determining fan

static pressure will not be made directly at the fan

inlet and outlet, but at locations a relatively short

distance upstream from the fan inlet and downstream

from the fan outlet. These static pressure

measurements are designated Ps4 and Ps5,

respectively. Static pressure at the fan inlet, Ps1, is

derived as follows:

Pt4 = Pt1 + ΔP4,1

Where:

Pt4 = the total pressure plane of measurement

Pt1 = the total pressure at the fan inlet

ΔP4,1 = the sum of the pressure losses between the

two planes

These losses (ΔP) include those attributable to duct

friction, duct fittings, other system components, and

changes in airway area. Although ΔP represents a

loss in all cases, it is considered a positive value as

used in the equations in this publication. By

substitution and rearrangement:

Ps1 = Ps4 + Pv4 - Pv1 - ΔP4,1

Similarly, for static pressure at the fan outlet, Ps2:

Pt2 = Pt5 + ΔP2,5

Ps2 = Ps5 + Pv5 - Pv2 + ΔP2,5

PP

sx

sxr

number of readings= ∑

AMCA 203-90 (R2007)

11

Where:

The velocity pressures at the various planes can be

determined from the following general equations for

the velocity pressure at a plane of measurement (x):

Pvx = Pv3 (A3/Ax)2 (ρ3/ρx)

Or:

Pvx = (Qx/1096Ax)2 ρx

Locate the static pressure measurement planes such

that the pressure losses between the measurement

planes and the planes of interest are insignificant.

This will eliminate the uncertainties involved in the

determination of the pressure losses, and the

equations for Ps1 and Ps2 reduce to the following:

Ps1 = Ps4 + Pv4 - Pv1

Ps2 = Ps5 + Pv5 - Pv2

These equations may be used when changes in area

between the measurement planes and the planes of

interest are moderate and gradual, and the pressure

losses associated with conversions of velocity

pressure to static pressure are negligible.

If, in addition to the losses being negligible there are

no changes in the areas between the measurement

planes and the respective planes of interest, then the

equations are further reduced to:

Ps1 = Ps4

Ps2 = Ps5

These equations may also be used when the only

losses between the measurement planes and the

planes of interest are those associated with changes

in area that are abrupt and sizable enlargements in

the direction of flow. This assumes that the velocity

pressure in the larger area is negligible.

10.4.3 Fan static pressure. The equation for fan

static pressure is:

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2 + ... + SEF n

Where:

SEF 1, SEF 2, ... SEF n = System Effect Factors that

account for the various System Effects that are

uncorrected and exist at the time of the field test.

10.5 Accuracy

The uncertainty analyses in Annex T indicate that the

uncertainties in fan static pressure determinations

are expected range from 2% to 8%. This range is

based on considerations of the conditions expected

to be encountered in most field test situations.

Improve the accuracy of the fan static pressure

determination by avoiding static pressure

measurement plane locations where turbulence or

other unsteady flow conditions will produce

significant uncertainties in the mental averaging of

pressure readings. Other reading resolution

uncertainties are not as significant in the fan static

pressure determination as in the determination of

flow rate. Generally, static pressure measurements

are much greater in magnitude than velocity pressure

measurements, and the selection of a manometer

that will provide reasonably good accuracy is not

usually a problem.

The uncertainty analyses in Annex T and the

resulting anticipated uncertainty range do not

account for uncertainties that may occur in the

following:

• Determinations of velocity pressure conversions

occurring between the measurement planes and

the planes of the fan inlet or fan outlet. The area

and density values that are involved in these

determinations are usually obtained without

significant uncertainties. However, pressure

losses associated with velocity pressure

conversions are often difficult to determine

accurately.

• Determinations of other pressure losses

occurring between the measurement planes and

the fan inlet or fan outlet. This includes pressure

losses in ducts, duct fittings, and other system

components. The calculations of these losses

are based on the assumption of uniform flow

conditions. This assumption may not be valid,

and the calculated pressure loss values may be

significantly inaccurate.

• Determinations of the values of System EffectFactors. These determinations are based on

limited information, and as such, are subject to

uncertainty.

Avoid situations requiring these determinations,

thereby eliminating them as sources for uncertainties.

The uncertainties involved in determining the values

of System Effect Factors can be avoided only by

correcting the causes of the System Effects. This

requires alterations to the system.

AMCA 203-90 (R2007)

12

11. Fan Power Input

11.1 General

Fan power input data included as part of the fan

performance ratings are normally defined and limited

to either:

• power input to the fan shaft

• the total of the power input to the fan shaft and

the power transmission loss

The losses in fan shaft bearings are included in either

case. Since the results of field tests are usually

compared to the rated performance characteristics of

the fan, field test values of fan power input should be

determined on the same basis as that used in the fan

ratings. For belt driven fans, the rated fan power input

may or may not include belt drive losses. The

information regarding the basis of the rated fan

power input accompanies the rating data or is

otherwise available from the fan manufacturer. In

most instances, when a power transmission loss

occurs, the loss will have to be determined and

subtracted from the motor output in order to obtain

the fan power input.

11.2 Power measurement methods

In view of the fact that accuracy requirements for field

test determinations of fan power input vary

considerably, a number of test methods are

recommended. These methods are intended to

provide economical and practical alternatives for

dealing with various levels of accuracy requirements.

11.2.1 Phase current method. This method for

estimating the power output of three phase motors is

based on the relationship of motor current and motor

power output. The method, described in Annex K,

requires measurements of the phase currents and

voltages supplied to the motor while driving the fan.

Depending on the operating load point of the motor, it

may also involve the measurements of the no load

phase currents.

The phase current method is convenient and

sufficiently accurate for most field tests. In this

method, the closer the actual phase current is to the

motor nameplate value of full load amps, the greater

the accuracy. Since fan motors are normally selected

for operation at or near the full load point, this method

provides a reasonably accurate estimate of the

power output of the fan motor. Determine fan power

input by using the motor power output and, where

applicable, the power transmission loss.

11.2.2 Typical motor performance data. Typical

motor performance data may be used to determine

fan power input. These data, which are referred to as

typical in that the data and the actual performance of

the motor are expected to correspond closely, can

usually be obtained from the motor manufacturer.

The data provided can be in a variety of forms, but

are sufficient to determine motor power output based

on electrical input measurements. It is important that

the power supplied to the motor during the field test

be consistent with that used as the basis for the

motor performance data. The phase voltage should

be stable and balanced, and the average should be

withing 2% of the voltage indicated in the

performance data.

Depending on the form of the typical motor

performance data, motor power output is determined

by one of the following methods:

1) Given the typical motor performance chart ofwatts input versus motor power output at a statedvoltage.

Hmo, is the value in the typical motor performance

data that corresponds to the field test

measurement of watts input to the motor.

2) Given the typical motor performance chart ofwatts input versus torque output and speed at astated voltage.

Use the field test measurement of watts input

and the corresponding typical motor performance

data values of torque output and speed; the

motor power output is calculated as:

3) Given the typical motor performance chart ofwatts input versus motor efficiency at a statedvoltage.

Use the field test measurement of watts input

and the corresponding typical motor performance

data value of motor efficiency, the motor power

output is calculated as:

4) Given the typical motor performance chart ofamps versus power factor and motor efficiency ata stated voltage.

Use the field test measurements of amps input

and volts, and the typical motor performance

data values of power factor (pf) and motor

efficiency, corresponding to the measured amps

input; the motor power output is calculated as:

H watts input motor efficiencymo = ×

746

H T Nmo = ×

63025

AMCA 203-90 (R2007)

13

Or, for three phase motors:

In both equations, amps and volts are the field test

measurement values and, in the case of three phase

motors, are the averages of the measured phase

values.

The fan power input is the motor power output minus

the power transmission loss, where applicable.

11.2.3 Calibrated motors. A calibrated motor may be

used to determine fan power input. When intending

to use this method, it is usually necessary to specify

in the motor purchase arrangements that the motor

be calibrated since an additional cost is normally

involved. Calibration data are similar to typical motor

performance data with the exception that, instead of

being merely typical, the calibration data represent

the performance of a specific motor, based on a test

of the motor. The motor is calibrated over a range of

operation. Electrical input data and other data

sufficient for the determination of power output are

obtained in the calibration. The calibration normally

provides data for operation at nameplate voltage, but

may include data for operation at voltages 10%

greater and 10% less than nameplate voltage. It is

important that the power supplied to the motor during

the field test be consistent with that used in its

calibration. The phase voltage should stable and

balanced, and the average should be within 2% of

the voltage at which the motor was calibrated. The

field test measurements and the calculations

involved in the determination of motor power output

are the same as those described in Section 11.2.2 for

use with typical motor performance data. The fan

power input is the motor power output minus the

power transmission loss, where applicable.

A calibrated motor provides accurate data to

determine motor power output. However, the cost of

the calibration is a limiting factor in the use of this

method in field tests. For low horsepower

applications, the fan manufacturer may be able to

calibrate a motor.

11.2.4. Torquemeters. Another method to determine

fan power input involves the use of a torquemeter

installed between the fan and the driver. The use of a

torquemeter requires some prearrangement with the

purchaser, who would normally have specified such

equipment, so that site conditions can be altered to

accommodate its installation. The torquemeter is

extremely limited in field test application. This is due

mainly to is high cost and the cost of its installation.

In addition, the length of the shut down time and the

revisions to site conditions required for its installation

are usually undesirable. For practical considerations,

it is not normally used in cases where the fan is belt

driven and where the fan impeller is installed directly

on the motor shaft.

11.3 Power measuring instruments

Measurement of current, voltage, watts, and power

factor can be obtained by using an industrial type

power analyzer of good quality. This type of

instrument is available with accuracies of 1% full

scale for volts, amps and power factor, and 2% full

scale for watts. Normally, the higher levels of

accuracy requirements can be met by using this type

of instrument, providing the measurements are well

up on the scales.

In many cases, accuracy level requirements will

permit the use of a clip-on type ammeter-voltmeter.

Clip-on instruments with accuracies of 3% full scale

are available.

11.4 Power transmission losses

Several types of power transmission equipment are

used in driving fans. Those in which power

transmission losses should be considered in the

determination of fan power input include belt drives,

gear boxes, fluid drives, and electromechanical

couplings.

Information as to whether the fan power input ratings

include power transmission losses is included in the

published performance ratings or is otherwise

available from the fan manufacturer. It is important

that this be established and that the fan power input

be determined accordingly in order to provide a valid

comparison of field test results to the fan

performance ratings. In most cases, fan power input

ratings do not include power transmission losses.

11.4.1 Estimating belt drive losses. In view of the

lack of published information available for use in

calculating belt drive losses, a graph is included in

Annex L for this purpose. As indicated in the graph,

belt drive loss, expressed as a percentage of motor

power output, decreases with increasing motor

power output and increases with increasing speed.

This graph is based on the results of over 400 drive

loss tests provided to AMCA by drive manufacturers.

The graph serves as a reasonable guide in

evaluating belt drive losses. The calculation of belt

drive loss, using this graph, is included in many of the

examples in Annex A.

H amps volts pf motor efficiencymo = × × ×

746

H amps volts pf motor efficiencymo = × × × ×( ) .3

746

0 5

AMCA 203-90 (R2007)

14

11.4.2 Estimating other transmission losses. For

other types of power transmission equipment, consult

the fan manufacturer to establish whether

transmission losses are included in the fan ratings,

and if so, request the magnitudes of the losses

allowed in the ratings. Otherwise, it will be necessary

to consult the manufacturer of the power

transmission equipment for the information regarding

transmission losses.

11.5 Accuracy

The uncertainty analyses presented in Annex T

indicate that the uncertainties in fan power input

determinations are expected to range from 4% to 8%.

This range is based on considerations of the

conditions encountered in most field test situations,

estimated accuracies of the various test methods

presented in this publication and allowances for

uncertainties in the determinations of power

transmission losses.

12. Fan Speed

12.1 Speed measuring instruments

Measure speed with a revolution counter and

chronometer, a stroboscopic tachometer, an

electronic counter-timer, or any other precision type

tachometer which has a demonstrated accuracy of

0.5% of the measured value. Friction driven and

magnetic type pickups should not be used in low fan

power ranges where they can influence speed and

fan power input measurements.

12.2 Speed measurements

Establish the speed by averaging a minimum of three

measurements made during the test determination

period. The variation in the measurements should not

exceed 1% for any single point of operation.

13. Densities

13.1 Locations of density determinations

Determine the densities of the gas stream for Plane

1, the fan inlet; and for Plane 3, the velocity pressure

measurement plane. In addition, the density at Plane

2, the fan outlet, must be determined whenever the

fan total pressure, the fan velocity pressure, or an

SEF at the outlet side of the fan is required.

13.2 Data required at each location

The pressure and temperature of the gas stream

must be obtained for each plane at which a density

determination is required. The pressures at Planes 1

and 2 are based on the static pressure

measurements made for the purpose of determining

the fan static pressure. The pressure at Plane 3 is

obtained by averaging static pressure measurements

made concurrent with the velocity pressure

measurements made in a traverse of Plane 3. The

absolute pressure at a plane is calculated by using

the static pressure at the plane and the barometric

pressure. For this reason, it is important that the

barometric pressure be determined for the

atmosphere to which static pressure measurements

are referred. The temperatures used in density

determinations are measured at the planes of

interest.

13.3 Additional data

Additional data required in the determination of

density depends on the gas stream as indicated

below:

1) For air, the wet-bulb temperature is required

unless it is otherwise known that the air is

saturated with water vapor or that the water

vapor content of the air is insignificant. It should

be noted that incorrect assumptions as to

whether the air is dry or saturated can result in

substantial errors in density determinations.

2) For gases other than air, the normal procedure is

to rely on process personnel for the data

necessary to determine the density of the gas.

The information provided will include density or

data sufficient to calculate the density, which

should be for stated conditions of temperature

and pressure.

13.4 Density values

Gas stream density can be established when the

pressure, temperature, and additional data, as

indicated in Section 13.3, have been obtained.

Procedures for establishing density are described in

the examples in Annex M and are further illustrated in

the field test examples in Annex A.

Although the pressure and temperature of the gas

stream must be obtained for each plane at which a

density value is required, it is usually necessary to

obtain additional data, such as the wet-bulb

temperature, for only one plane in order to establish

the densities at all planes. The densities at the planes

for which the additional data is not obtained can be

calculated, providing the gas stream does not change

composition or undergo a change in phase between

planes. The calculation is based on density being

directly proportional to absolute pressure and

AMCA 203-90 (R2007)

15

inversely proportional to absolute temperature.

13.4.1 Example calculation - ρ3 from ρ1. Use Figure

N.1 of Annex N to establish the density of air at Plane

1 based on the test determinations of barometric

pressure, pb, and the following Plane 1 values:

Ps1, static pressure, in. wg

td1, dry-bulb temperature, °F

tw1, wet-bulb temperature, °F

The following data are obtained for Plane 3:

Ps3, static pressure, in. wg

td3, dry-bulb temperature, °F

Calculate the density at Plane 3 as follows:

Where:

p1 = the absolute pressure, in. Hg at Plane 1,

calculated as follows:

p1 = pb + (Ps1/13.6)

In this manner, ρ3 can be calculated without having to

measure the wet-bulb temperature at Plane 3. These

equations can be used for gases other than air and

can be adapted for use in calculations involving any

two planes, subject to the limitations noted earlier.

In the example calculation of ρ3, pb is determined for

the atmosphere to which the measurements of Ps1

and Ps3 are referred. Refer static pressure

measurements to a common atmosphere. When

the pressures cannot be referred to a common

atmosphere, the absolute pressure for each plane is

calculated by using the static pressure measurement

at the plane and the barometric pressure for the

atmosphere to which the static pressure

measurement is referred. However, for the purposes

of accuracy, static pressure measurements that are

used in the determination of fan static pressure must

be referred to a common atmosphere.

13.5 Temperatures

Measure temperatures with mercury-in-glass, dial, or

thermocouple type thermometers. For temperatures

through 220°F, the thermometer should be accurate

within 2°F of the measured value and readable to 1°F

or finer. For temperatures above 220°F, the

thermometer should be accurate within 5°F of the

measured value and readable to 5°F or finer.

The temperature determination should be

representative of the average temperature of the gas

stream throughout the plane of interest. When the

temperature varies with time or temperature

stratification exists at the measurement plane,

several temperature measurements may be

necessary in order to obtain a representative

average. At elevated temperatures, the thermometer

may have to be shielded to prevent radiation effects

from exposed heat sources.

Locate the wet-bulb thermometer downstream from

the dry-bulb thermometer in order to prevent the dry-

bulb temperature measurement from being adversely

affected. The wet-bulb thermometer wick should be

clean, closely fitted, and wetted with fresh water. The

velocity of the air over the wick should be between

700 and 2000 fpm. Use a sling psychrometer to

obtain dry and wet-bulb air temperature

measurements at the fan inlet for free inlet fans.

13.6 Barometric pressure

Use a portable aneroid barometer for field test

determinations of barometric pressure when an

acceptable site barometer is not available. The

barometer should be accurate within 0.05 in. Hg of

the measured value. Determine the test value of

barometric pressure by averaging measurements

made at the beginning and end of the test period.

When the test value of barometric pressure is to be

based on data obtained from a nearby airport, it is

important that the data include the barometric

pressure for the airport site and the elevation for

which the pressure was determined (often the

barometric pressure is corrected to sea level). This

pressure value must then be corrected to the test site

elevation. Barometric pressure decreases

approximately 0.1 in. Hg for every 100 ft increase in

elevation

13.7 Accuracy

As indicated in Annex T, uncertainties in density

determinations are expected to be less than 3%.

However, care must be exercised in obtaining

representative test measurements in order to prevent

the uncertainties from exceeding this value.

14. Conversion Calculations

Generally, the test fan will be operating at a speed

and inlet density that are somewhat different from the

ρ ρ3 1

13 6

13 6

460

460= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

P pp

tt

s3 b

1

d1

d3

.

.

AMCA 203-90 (R2007)

16

fan performance rating values of fan speed and inlet

density. In order to provide a common basis for

comparing the field test results to the fan

performance ratings, each of these two items must

be the same in both sets of data. This can be

accomplished by converting the results of the field

test to the speed and density conditions of the fan

performance ratings. The equations for the

conversion are as follows.

Qc = Q (Nc / N)

Psc = Ps (Nc / N)2 (ρc / ρ)

Ptc = Pt (Nc / N)2 (ρc / ρ)

Pvc = Pv (Nc / N)2 (ρc / ρ)

Hc = H (Nc / N)3 (ρc / ρ)

Where the subscript c designates values converted

to specified conditions, and items without the

subscript c are field test values.

These conversion equations do not account for the

effect of the compressibility of the gas stream.

However, since the test fan usually operates at

conditions of speed and inlet density that are

reasonably close to the quoted fan performance, the

conversion calculations usually result in small

changes from field test values and the effect of the

compressibility of the gas stream is considered to be

negligible. Where test conditions are considerably

different than design conditions, the effect of

compressibility may need to be considered.

15. Test Preparation

15.1 The following items should be agreed upon by

all interested parties prior to the start of a field

performance test:

1) AMCA Publication 200, Air Systems, AMCA

Publication 201, Fans and Systems, and AMCA

Publication 202, Troubleshooting, should be

reviewed and implemented before starting the

field test.

2) Personnel conducting field tests on fans must be

technically competent and fully conversant with

all four parts of the AMCA Fan Application

Manual. The person responsible for conducting

the test should be designated and agreed upon

by all parties.

3) The test instrumentation and locations of test

measurement planes should be established.

Work required to accommodate test

measurements (drilling of traverse holes,

installation of static pressure taps and

thermometer wells, etc.) should be completed

prior to the test date.

4) System Effect Factors, if any, must be

established prior to the conduct of the test.

5) The expected test uncertainties must be agreed

upon prior to the test (see Annex T).

6) Responsibility for the cost of the test or any fan-

system modifications required as a result of the

test should be established.

7) Prior to testing, an inspection must be made to

ensure that the fan is installed in accordance with

the fan manufacturer’s recommendations. The

duct system should also be inspected for

compliance with design specifications, conditions

of filters, abnormal duct restrictions, etc.

8) The majority of fan field performance tests cover

a single point of operation, namely, the design

duty. If it is deemed necessary to cover several

points of operation, provision must be made in

advance for changing the system resistance. The

means used to vary the system resistance must

not cause adverse flow conditions in the vicinities

of the fan and measurement planes. If the fan

cannot be tested at the quoted system design

point, then it is sufficient for the evaluation of fan

field performance to establish the proximity of the

field test point to any portion of the fan

performance rating curve within the limitations of

the uncertainty analysis (see Annex T).

9) It must be established that the system remains

constant for the duration of the test. Modulating

dampers should be set in a fixed position, no

process changes shall be undertaken, etc.

Variable inlet vane controls or inlet box dampers

must be set in the full open position for the

duration of the test, except when testing for

control characteristics.

10) All precautions to ensure the safety of test

personnel must be observed.

11) The fan-system should be operated for a length

of time sufficient to ensure steady state

conditions prior to the start of the test.

12) It is advisable that representatives of all parties

interested in the test results be present at the

time of the test to cover their areas of

responsibility.

AMCA 203-90 (R2007)

17

15.2 It is recommended that as a minimum, the

following equipment be taken to or be otherwise

available at the job site:

1) Pitot-static tubes of suitable lengths for the

maximum duct size to be traversed.

Considerations should be given to the use of a

double reverse tube in dirty atmospheres.

2) Manometers suitable for measuring static

pressures. Manometer fluids other than water are

acceptable, provided the specific gravity is

known. A spare bottle of manometer fluid is

advisable.

3) Inclined manometer suitable for measuring

velocity pressures.

4) Flexible tubing of suitable length to enable

manometers to be installed at a convenient

location.

5) Tubing couplings and “T” type tubing connectors.

6) Thermometers to cover the range of anticipated

temperatures.

7) Sling psychrometer for obtaining dry-bulb and

wet-bulb temperatures.

8) Clip-on ammeter-voltmeter, power analyzer, or

other suitable electrical measurement

instruments for the determination of fan power

input.

9) Fan speed measurement instrument.

10) Aneroid barometer.

11) Flashlight, tape, measuring rule, hand tools,

coveralls, etc.

12) Test data sheets, calculator, and necessary

drawings.

13) Complete AMCA Fan Application Manual

containing Publications 200, 201, 202, and 203.

16. Precautions

The following precautions should be observed when

conducting a field test:

1) Connect the Pitot-static tube to the manometers

according to anticipated pressures, i.e., whether

the pressures are positive or negative, and the

magnitudes of pressures.

2) Static and total pressure manometer tubing must

be “pinched off” prior to inserting or removing the

Pitot-static tube from the test duct. Release both

legs of the tubing simultaneously after the Pitot-

static tube is inside the test duct and properly

oriented. Failure to release simultaneously may

result in manometer fluid being blown from the

manometer.

3) Loop the manometer tubing well above the

manometer so that any fluid which is

inadvertently blown from the gauge will drain

back into the manometer.

4) The Pitot-static tube is intended for measuring

pressures in relatively clean gases. When using

Pitot-static tubes in dirty, wet, or corrosive

atmospheres, both legs of the Pitot-static tube

must be cleaned out frequently during the test.

Since fan pressure readings are never strictly

steady, absence of fluctuations is an

indication of a plugged Pitot-static tube.

Consider using a double reverse tube in these

situations.

5) When making measurements in wet gas

streams, continually check for the presence of

moisture in the tubing. Clear plastic tubing is

ideal from this standpoint. If moisture collects in

the tubing, immediately remove the Pitot-static

tube and clean the inside of the tubing and Pitot-

static tube before proceeding with the test.

6) Before performing any work inside a fan,

ductwork, or other system components, make

certain that the fan motor starter is “locked out.”

7) The area at the plane of flow measurement

should be measured internally to account for

internal insulation or other obstructions.

8) Do not rely on damper control indicators to

ensure that dampers are fully open. Check

visually.

9) Measure temperatures on both sides of double

inlet fans as temperature differences may exist

between each side.

10) When measuring in high temperature, corrosive

or explosive atmospheres, instruments should be

selected for suitability for such atmospheres.

17. Typical Fan-System Installations

A fan assembly may include any number of

appurtenances: variable inlet vanes, inlet boxes, inlet

AMCA 203-90 (R2007)

18

box dampers, outlet dampers, inlet screens, belt

guards, inlet bells, diffusers (evasés). Alternately,

these items may be included in the fan-system

installation, but not be a part of the fan assembly. In

order to determine the proper field test procedure

and to provide a valid basis for comparing field test

results to the fan performance ratings, it is important

to establish which of these items are considered a

part of the fan and which are considered a part of the

system. The fan performance ratings may be

assumed to include the appurtenances that are

established as being a part of the fan assembly.

The locations of the fan inlet and fan outlet depend

on whether specific appurtenances are considered

to be a part of the fan assembly. If the assembly

includes an inlet box, the fan inlet is the inlet to the

inlet box. For a fan assembly that includes a diffuser,

the fan outlet is the outlet of the diffuser.

In the case of heating, ventilating, and air-

conditioning equipment, the field test procedure will

depend on whether the equipment is a factory

assembled central station unit, a built-up unit, or a

packaged unit (see Section 17.4).

The performance ratings for a fan that includes inlet

box dampers, variable inlet vanes or outlet dampers

cover operation of the fan with these items in the full

open positions. In order to be able to compare the

field test results to the fan performance ratings, it is

essential that these items be fixed in their full open

positions for the duration of the test. In addition, when

the loss through a damper must be calculated, it is

essential that the damper blades be fixed in their full

open positions during the test since this is the

condition on which the damper pressure loss ratings

are based. This consideration arises when a damper,

which is not considered a part of the fan is located

between a static pressure measurement plane and

the fan. In order to determine the fan static pressure,

the loss through the damper must be calculated. In

these cases, the calculation of the loss is based on

the performance ratings for the damper.

17.1 Free inlet, free outlet fans

It is difficult to achieve an accurate field test of a free

inlet, free outlet fan. The most obvious problem is the

lack of a suitable location for the velocity pressure

measurement plane. In addition, in the case of

ventilators that supply or exhaust air from a building-

the most commonly encountered applications of free

inlet, free outlet fans-it is extremely difficult to define,

set, and maintain for the duration of the test the

“normal” system condition. Items affecting the system

include:

a) The operations of ovens, furnaces, paint booths,

air conditioning equipment, other fans, and

similar items that may supply or exhaust air from

the building in intermittent or modulating

fashions.

b) The use of doors providing access to the

building. The effect is most significant when large

doors that are normally closed are kept open for

extended periods such as in loading operations.

c) The velocity and direction of the wind outside the

building, particularly in conjunction with the item

immediately above and as it may affect the flow

of air from the outlet of the ventilator.

d) The use of interior doors that my restrict the flow

of air from areas normally expected to be

ventilated.

Assuming that these difficulties can be resolved and

the desired system is fixed for the duration of the test,

determine the fan performance by using one of the

following methods:

1) Make field test measurements sufficient for

determining fan static pressure, fan power input,

fan speed, and the density of the air at the fan

inlet. In this method for testing a free inlet, free

outlet fan, the fan static pressure is calculated as

the static pressure on the outlet side of the fan

less the static pressure on the inlet side of the

fan: Ps = Ps2 - Ps1. The static pressure

measurements involved must be referred to the

same atmospheric pressure and made at

locations sufficiently distant from the fan inlet and

outlet so as to be unaffected by the velocity of the

air entering and leaving the fan. Using the fan

manufacturer’s certified performance ratings,

draw a performance curve for the fan for

operation at the test values of fan speed and

entering air density. Determine the fan air flow

rate by entering this curve at the test values of

fan static pressure and fan power input (see

Example 5C in Annex A).

2) Use the method as described above with the

exception that the performance curve is

established by a laboratory test of the fan,

conducted in accordance with AMCA Standard

210. For the laboratory test, the fan must be set

up in a manner that duplicates the field

installation conditions. That is, all appurtenances

must be in place and any restrictions or

obstructions to the free flow of air into the fan

inlet and away from the fan outlet must be

accurately duplicated in the laboratory test setup.

AMCA 203-90 (R2007)

19

3) Install a duct on the inlet side of the fan for the

purpose of providing a location for the velocity

pressure measurement plane. All of the test

measurements and calculations in this method

for testing a free inlet, free outlet fan are the

same as those required for a fan with a ducted

inlet and a free outlet. The cross-sectional shape

and area of the duct, which is temporarily

installed for purposes of the test, should be

selected on the basis of minimizing its

interference with the flow of air into the fan inlet

while providing velocity pressure of magnitudes

that can be accurately measured. The length of

the duct should be a minimum of twice its

diameter or equivalent diameter, and the

entrance to the duct should be flared in order to

reduce the entrance loss. The velocity pressure

measurement plane should be located a

minimum of 1.5 diameters or equivalent

diameters downstream from the duct inlet. The

effect of this duct on the system is negligible, but

in changing the pattern of the flow of air into the

fan inlet, it may affect the performance of the fan

slightly. Applications of this method of test are

presented in Examples 5A and 5B in Annex A.

The equation for calculating fan static pressure

for this configuration is:

Ps = Ps2 - (Ps1 + Pv1)

17.2 Free inlet, ducted outlet fans

In the calculation of fan static pressure for this type of

fan-system configuration, the sum of the static

pressure at the fan inlet, Ps1, and the velocity

pressure at the fan inlet, Pv1, is considered to be

equal to the sum of the static pressure, Psx, and the

velocity pressure, Pvx, at a point sufficiently distant

from the fan inlet as to be in still air. At this point, the

static pressure is zero, and the velocity pressure in

still air is zero.

Ps1 + Pv1 = Psx + Pvx = 0

This consideration, which is the same as that used in

the methods for testing fans for performance rating

purposes, charges to the fan the losses incurred in

accelerating the air into the fan inlet and eliminates

inaccuracies which may occur in any attempt to

measure velocity pressure and static pressure at the

fan inlet. Since Ps1 + Pv1 = 0, the equation for

calculating fan static pressure for this configuration

is:

Ps = Ps2 + SEF 1 +SEF 2 + ... + SEF n

17.3 Ducted inlet, ducted outlet fans

In this type of fan-system configuration, there is no

special consideration in the calculation of fan static

pressure. The equation for this calculation is:

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2 + ... + SEF n

In this configuration, the flow conditions on the inlet

side of the fan are usually more favorable for the

location of the velocity pressure measurement plane.

17.4 Ducted inlet, free outlet fans

In this type of fan-system configuration, the static

pressure at the fan outlet, Ps2, is zero gauge

pressure, referred to the atmospheric pressure in the

region of the fan outlet. However, the gas stream may

be discharging from the fan into a region in which the

atmospheric pressure is somewhat different from that

to which all other pressure measurements are

referred. When this possibility exists, it is essential

that the static pressure measurements in the region

of the fan outlet be referred to the same atmospheric

pressure as used in all other pressure

measurements.

Ps = -Ps1 - Pv1 + SEF 1 + SEF 2 + ... + SEF n

17.5 Air handling units

This category consists of draw-through and blow-

through types of equipment assemblies used in

heating, ventilating, and air-conditioning applications.

In addition to fans, these equipment assemblies may

include any number of combinations of coils, filters,

access sections, humidifiers, mixing boxes, dampers,

etc. Air handling units include packaged units, factory

assembled central station units, and built-up units.

The basis used in establishing the air performance

ratings for each of these unit types is described

below. It is important that the field test method

correspond to the rating method in each case.

17.5.1 Packaged units. This type of unit is supplied

and rated by the manufacturer as an assembly. The

static pressures at the inlet and outlet to the

assembly and the velocity pressure at the inlet to the

assembly are used in calculating the static pressure

generated by this type of air handling unit. See

Examples 4C and 4D in Annex A.

17.5.2 Factory assembled central station units.

The air performance ratings for this type of unit are

based on the operation of the fan section assembly

only, but include the effects of the air flow conditions

AMCA 203-90 (R2007)

20

entering and leaving the fan section which are

created by accessory equipment such as plenums,

coils, filters, mixing boxes, etc. The fan section

assembly includes the fan and the cabinet in which

the fan has been installed. The accessory items are

considered to be included in the system in which the

fan section operates. The static pressure and the

velocity pressure at the inlet of the fan section and

the static pressure at the fan section outlet, which

coincides with the fan outlet, are used in calculating

the static pressure generated by the fan section

assembly. See examples 4B and 4E in Annex A.

17.5.3 Built-up units. Built-up units are similar to

factory assembled central station units, except that in

built-up units, the components are normally obtained

from a number of equipment suppliers and the unit is

assembled at the installation site. The fans which are

used in built-up units are rated as free-standing,

unencumbered by the cabinets in which they are

installed. In the field test determination of the

performance of the fan, the static pressure and

velocity pressure at the fan inlet and the static

pressure at the fan outlet are used in calculating the

fan static pressure. An SEF that accounts for the

effect of the cabinet is normally included in this

calculation, and it may be necessary to include an

SEF to account for the conditions at the fan outlet.

See Example 4A in Annex A.

AMCA 203-90 (R2007)

21

AMCA 203-90 (R2007)

Annex A. Field Test Examples

This annex contains examples of field tests. The examples are presented in detail and cover several types of fan-

system combinations. Field test procedures are illustrated in a variety of situations. Portions of the procedures are

typical for all fan-system installations. Other portions of the procedures demonstrate methods for dealing with the

more difficult features encountered in some installations. Not all of the possible fan-system combinations are

included in the examples, but it is expected that the examples will provide sufficient guidance for dealing with those

cases not covered.

EXAMPLES OF FANS, INSTALLATION TYPE B: FREE INLET, DUCTED OUTLET

1A: Centrifugal Forced Draft Fan

1B: Centrifugal Forced Draft Fan with Inlet Silencers

1C: Axial Forced Draft Fan with Inlet Silencers

1D: Centrifugal Fans in Parallel

EXAMPLE OF FANS, INSTALLATION TYPE D: DUCTED INLET, DUCTED OUTLET

2A: Utility Fan in a Ventilating System

2B: Centrifugal Fan in a Sawdust Conveying System

2C: Axial Fan in a Dryer System

2D: Centrifugal Fan in a Scrubber System

2E: Centrifugal Fan in a Process System

2F: Axial Fan in a Ventilation System

2G: High Pressure Centrifugal Fans in Series

EXAMPLES OF FANS, INSTALLATION TYPE C: DUCTED INLET, FREE OUTLET

3A: Centrifugal Fan in an Exhaust System

3B: Axial Fan in an Exhaust System

3C: Centrifugal Fan in a Scrubber System

3D: Centrifugal Roof Ventilator with Ducted Inlet

EXAMPLES OF AIR HANDLING UNITS

4A: Centrifugal Fan in a Built-up Air conditioning Unit

4B: Central Station Air Conditioning Unit, Factory Assembled Draw-Through Type

4C: Packaged Air Conditioning Unit

4D: Packaged Air Conditioning Unit

4E: Central Station Air Conditioning Unit, Factory Assembled Blow-Through Type

EXAMPLES OF FANS, INSTALLATION TYPE A: FREE INLET, FREE OUTLET

5A: Free Inlet, Free Outlet Roof Ventilator with temporary duct

5B: Free Inlet, Free Outlet Propeller Fan with temporary duct

5C: Free Inlet, Free Outlet Roof Ventilator as installed

22

AMCA 203-90 (R2007)

1. The variable inlet vanes are considered part of the

fan. Performance ratings for fans with inlet vanes

cover operation with the inlet vanes in their full open

position. In order to be able to compare the test

results to the fan performance ratings, it is essential

that the inlet vanes be fixed in their full open positions

for the duration of the test.

2. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located near the end of the fan

diffuser (evasé). Determine Ps3 by averaging the

static pressure measurements made in the same

traverse. Procedures for the traverse are described in

Section 9.4. These velocity pressure and static

pressure measurements are susceptible to error due

to the turbulence existing in the region of the fan

outlet. In addition, it is undesirable to have Plane 3

located in a diverging airway. However, no other

more suitable location for Plane 3 exists in this

example. It is recommended that the Pitot-static tube

be oriented so that its nose is aligned with the

anticipated flow streams, particularly near the walls of

the diffuser, as shown in the diagram. Determine the

area of the traverse plane, A3, which is located at the

tip of the Pitot-static tube, as shown in the diagram,

not at the location of the Pitot-static tube access

holes in the diffuser.

3. Measure td1 and tw1 in the path of the air flowing

into the fan inlets. Determine pb for the general

vicinity of the fan. Measure td3 in Plane 3. All of these

measurements are used in the determination of

densities at the various planes of interest.

4. Measure the fan speed and the motor amps, volts,

and, if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV) and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point (refer to Annex K).

5. SEF 1 is due to the effect of insufficient length of

duct at the fan outlet. In order to calculate the value

of SEF 1, it is necessary to measure the length of the

outlet duct, L; the outlet area of the fan, A2; and the

blast area of the fan.

6. The sum of the static pressure, Ps1, and velocity

pressure, Pv1, at the inlets of a fan with unrestricted

inlets is considered to be equal to the sum of the

static pressure, Psx, and the velocity pressure, Pvx, at

a point sufficiently distant from the fan inlets as to be

in still air. At this point, the static pressure is zero, and

EXAMPLE 1A: CENTRIFUGAL FORCED DRAFT FAN

ORIENTATIONOF PITOT TUBE

23

A2

A3

LOCATIONS OFPLANES 2 AND 3

OUTLET SIDE VIEWSIDE VIEW

VARIABLEINLET VANES

DIFFUSERSEF 1

L

COMMENTS

23

the velocity pressure in still air is zero.

Ps1 + Pv1 = Psx + Pvx = 0

This consideration, which is the same as that used in

the methods for testing fans for performance rating

purposes, charges to the fan losses incurred in

accelerating the air into the fan inlets and eliminates

the inaccuracies which arise in any attempt to

measure the velocity pressure and static pressure at

the fan inlets. To calculate the fan static pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= Ps2 - (Ps1 + Pv1) + SEF1

Since:

Ps1 + Pv1 = 0

Ps = Ps2 + SEF 1

7. In order to compare the test results to the quoted

fan curve drawn for operation at 1780 rpm and

0.0701 lbm/ft3 density, it is necessary to convert the

results to the specified conditions. In this case, the

test conditions are identical to the specified

conditions and no calculations are required.

OBSERVATIONS

SITE MEASUREMENTS

pb = 28.91 in. Hg

td1 = 85°F

tw1 = 63°F

td3 = 96°F

Ps3 = 14.4 in. wg

Pv3 = 1.52 in. wg

N = 1780 rpm

A2 = 11.94 ft2

A3 = 11.3 ft2

Blast Area = 7.76 ft2

L = 3 ft.

MEASURED MOTOR DATA

Volts = 570, 560, 572

= 567 av.

Amps = 160, 166, 163

= 163 av.

MOTOR NAMEPLATE DATA

200 hp, 3 phase, 60 hertz

575 volts, 1800 rpm, 181 FLA

GENERAL

VIVs in full open positions.

Fan direct connected to motor.

CALCULATIONS

DENSITIES

For fan inlet conditions of:

td1 = 85°F

tw1 = 63°F

p1 = pb

= 28.91 in. Hg

Use Figure N.1 in Annex N to obtain ρ1 = 0.0701

lbm/ft3

The density at Plane 3:

In this case, ρ2 is considered to be equal to ρ3.

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (1.52/0.0712)0.5

= 5064 fpm

Q3 = V3A3

= 5064 × 11.3

= 57223 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 57223 (0.0712/0.0701)

= 58121 cfm

FAN POWER INPUT

Measured amps/FLA = (163/181)

= 0.90

= 90%

Annex K indicates that Equation A will provide a

reasonably accurate estimate of motor power output

for a 200 hp motor operating at 90% FLA.

ρ ρ3 1

1

13 6

13 6

460

460

0 070114 4

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

P pp

tt

s3 b d1

d3

.

.

.. ++ ×

×⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

13 6 28 91

13 6 28 91

545

556

0 0712 3

. .

. .

. lbm/ft

AMCA 203-90 (R2007)

24

Hmo = 200 (163/181) (567/575)

= 178 hp

Since the fan is direct connected to the motor:

H = Hmo

= 178 hp

SYSTEM EFFECT FACTOR

AMCA Publication 201-90, Figures 7.1 and 8.3

indicate the following calculations:

Q2 = Q3 (ρ3/ρ2)

= 57223 (0.0712/0.0712)

= 57223 cfm

V2 = (Q2/A2)

= (57223/11.94)

= 4793 fpm

Duct diameter equivalent to the diffuser outlet area:

Figure 8.3 shows that for velocities over 2500 fpm,

100% effective duct length is one duct diameter per

1000 fpm,

= De2 (V2/1000)

= 3.9 (4793/1000)

= 18.7 ft

L in % effective duct length

= (L/18.7) 100

= (3/18.7) 100

= 16%

Blast area ratio = Blast Area/A2

= 7.76/11.94

= 0.65

For blast area ratio of 0.65, and 16% effective duct

length, Figure 8.3 shows System Effect Curve U

applies. For 4793 fpm velocity and curve U, Figure

7.1 shows SEF 1 = 0.6 in. wg at 0.075 lbm/ft3. At

0.0712 lbm/ft3.

SEF 1 = 0.6 (0.0712/0.075)

= 0.57 in. wg

FAN STATIC PRESSURE

Since A2 is greater than A3, there may be some

conversion of velocity pressure to static pressure

between Planes 3 and 2. However, the amount of

conversion will be very small relative to the static

pressure measured at Plane 3 and ignoring any

change in static pressure from Plane 3 to Plane 2 will

have no appreciable effect on the test results.

Therefore, Ps2 is considered equal to Ps3.

Ps = Ps2 + SEF 1

= 14.4 + 0.57

= 14.97 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = Q= 58121 cfm

Psc = Ps

= 14.97 in. wg

Hc = H= 178 hp

D Ae2

ft.

=

= ×( )=

4

4 11 94

3 9

2 /

. /

.

π

π

AMCA 203-90 (R2007)

25

AMCA 203-90 (R2007)

1. This fan, as supplied and rated by the

manufacturer, includes the variable inlet vanes and

inlet boxes, but does not include the silencers.

Performance ratings for fans with inlet vanes cover

operation with the inlet vanes in the full open

positions. In order to be able to compare the test

results to the fan performance ratings, it is essential

that the inlet vanes be fixed in their full open positions

for the duration of the test.

2. Determine Pv3a and Pv3b by using the root mean

square of the velocity pressure measurements made

in traverses of Planes 3a and 3b. A3a and A3b are the

areas traversed. Determine Ps3a and Ps3b by

averaging each of the two sets of static pressure

measurements made in the same traverses.

Procedures for traverses are described in Section

9.4. Ps3a and Ps3b are used in determining the density

at the traverse plane. A location for Plane 3

measurements may be obtained by installing ducts

on each silencer inlet, as shown in the diagram. The

ducts should be a minimum of one equivalent

diameter in length, and have flared inlets to reduce

entrance losses and provide more uniform velocity

profiles at the pressure measurement planes.

3. Measure Ps1a and Ps1b at locations close to the

entrances to the inlet boxes and in planes which are

substantially equal in area to the planes of the

entrances to the inlet boxes (Plane 1). Determine Ps2

by averaging the pressure measurements at each of

four static pressure taps located near the end of the

fan diffuser (evasé). See Annex E for details of static

pressure taps.

4. Measure td3 and tw3 near the inlet ducts. Determine

pb for the general vicinity of the fan. Measure td2 in

Plane 2. All of these measurements are used in the

determination of densities at the various planes of

interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV) and amps

(FLA). If the motor power output is to be estimated by

using the phase current method described in Annex

K, it is not necessary to measure motor watts;

however, it may be necessary to disconnect the drive

and measure the no load amps (NLA) if the motor is

not operating at or near its full load point. Refer to

Annex K.

6. SEF 1 is due to the effect of there being no duct

at the fan outlet. In order to calculate the value of

SEF 1, it is necessary to measure the fan outlet area,

A2, and the blast area of the fan.

7. To calculate the fan static pressure:

EXAMPLE 1B: CENTRIFUGAL FORCED DRAFT FAN WITH INLET SILENCERS

DIFFUSERSTATICPRESSURE TAPS

A2

SEF 1

2

1

SILENCERS

TEMPORARYDUCT

3a 3b0.5 De

OUTLET SIDE VIEWVARIABLE INLET VANES

SIDE VIEW

COMMENTS

26

Ps = Ps2 - Ps1 - Pv1 + SEF 1

Where:

Pv1 = (Q/1096A1)2 ρ1

8. In order to compare the test results to the quoted

fan curve drawn for operation at 1180 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.31 in. Hg

td2 = 93°F

td3 = 85°F

tw3 = 58°F

Ps1a = -1.20 in. wg

Ps1b = -1.30 in. wg

Ps2 = 10.1 in. wg

Ps3a = -0.65 in. wg

Ps3b = -0.70 in. wg

Pv3a = 0.61 in. wg

Pv3b = 0.62 in. wg

N = 1180 rpm

A1a = A1b

= 12.5 ft2

A2 = 18 ft2

A3a = A3b

= 12.5 ft2

Blast Area = 13.5 ft2

MEASURED MOTOR DATA

Volts = 460, 455, 465

= 460 av

Amps = 257, 256, 258

= 257 av

MOTOR NAMEPLATE DATA

200 HP, 3 phase 60 hertz

460 volts, 1180 rpm, 285 FLA

GENERAL

VIVs in full open positions. Fan direct connected to

motor. The motor manufacturer advises that this

motor type has a peak efficiency of 91% at a power

factor of approximately 0.89.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 85°F

tw3 = 58°F

Ps3 = (Ps3a + Ps3b)/2

= (-0.65 - 0.70)/2

= -0.675 in. wg

p3 = pb + (Ps3/13.6)

= 29.31 + (-0.675/13.6)

= 29.26 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0712

lbm/ft3

It is assumed that the temperature at Plane 1 are the

same as those at Plane 3. The density at Plane 1:

The density at Plane 2:

FLOW RATES

V3a = 1096 (Pv3a/ρ3)0.5

= 1096 (0.61/0.0712)0.5

= 3208 fpm

Q3a = V3aA3a

= 3208 × 12.5

= 40100 cfm

V3b = 1096 (Pv3b/ρ3)0.5

= 1096 (0.62/0.0712)0.5

= 3234 cfm

Q3b = V3bA3b

= 3234 × 12.5

= 40425 cfm

ρ ρ2 3

13 6

13 6

460

460

0 071210 1

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

P pp

tt

s2 b

3

d3

d2

.

.

.. ++ ×

×⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

13 6 29 31

13 6 29 26

545

553

0 0721

. .

. .

. lbm/ft3

ρ ρ1 3

13 6

13 6

460

460

0 07121 2

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= −

P pp

tt

s1 b

3

d3

d1

.

.

.. 55 13 6 29 31

13 6 29 26

545

545

0 0711

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

. .

. .

. lbm/ft3

AMCA 203-90 (R2007)

27

Q3 = Q3a + Q3b

= 40100 + 40425

= 80525 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 80525 (0.0712/0.0711)

= 80638 cfm

FAN POWER INPUT

Measured amps/FLA = (257/285)

= 0.90

= 90%

Annex K indicates that Equation A will provide a

reasonably accurate estimate of motor power output

for a 250 hp motor operating at 90% FLA.

Hmo = 250 (257/285) (460/460)

= 225 hp

As a check of this value, using the motor efficiency

data and the appropriate equation in Section 11.2.2:

Since the motor is not fully loaded, the power factor

and efficiency may be less, which would reduce Hmo

as calculated using the second method. However,

this is a reasonable check. The value of Hmo is

selected to be the average of the two results:

Hmo = 224 hp

Since the fan is direct-connected to the motor, there

is no drive loss, and:

H = Hmo

= 224 hp

SYSTEM EFFECT FACTOR

AMCA Publication 201-90, Figures 7.1 and 8.3

indicate the following calculations:

Q3 (ρ3/ρ2) = 80525 (0.0712/0.0721)

= 79520 cfm

(Q2/A2) = (79520/18)

= 4418 fpm

Blast area ratio = Blast Area/A2

= 13.5/18

= 0.75

For a blast area ratio of 0.75, and no duct, Figure 8.3

shows System Effect Curve T applies. For 4418 fpm

velocity and curve T, Figure 7.1 shows SEF 1 = 0.65

in. wg at 0.075 lbm/ft3. At 0.0720 lbm/ft3:

SEF 1 = 0.65 (0.0721/0.075)

= 0.62 in. wg

FAN STATIC PRESSURE

Pv1 = (Q1/1096 A1)2

= (80638/1096 × 25)2 0.0711

= 0.62 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= 10.1 - (-1.25) - 0.62 + 0.62

= 11.33 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = Q= 80638 cfm

Psc = 11.33 (0.075/0.0711)

= 11.95 in. wg

Hc = 224 (0.075/0.0711)

= 236 hp

Hmo

hp

= × × × ×

=

3 257 460 0 89 0 91

746

222

. .

AMCA 203-90 (R2007)

28

AMCA 203-90 (R2007)

1. This is a variable pitch axial flow fan. The fan

assembly, as supplied and rated by the manufacturer,

includes the inlet box and diffuser section, but does

not include the silencer. It is essential that the blade

pitch angle be fixed for the duration of the test. This

blade angle should be agreed upon by all interested

parties.

2. A temporary short duct is installed upstream of the

silencer to establish Plane 3 in which more uniform

pressures can be obtained. The duct should be a

minimum of one equivalent diameter in length, and

have a flared inlet to reduce entrance losses and

provide a more uniform velocity profile at the

pressure measurement plane. Determine Pv3 by

using the root mean square of the velocity pressure

measurements made in a traverse of Plane 3. Ps3 is

determined by averaging the static pressure

measurements made in the same traverse.

Procedures for traverses are described in Section

9.4. Ps3 is used in determining the density at the

traverse plane.

3. Measure Ps1 at a location close to the entrance to

the inlet box and in a plane which is substantially

equal in area to the plane of the entrance to the inlet

box (Plane 1). Determine Ps5 by averaging the

pressure measurements at each of four static

pressure taps located near the end of the fan diffuser.

See Annex E for details of static pressure taps. In this

example, Ps2 is considered to be equal to Ps5.

4. Measure td3 and tw3 near the entrance to the short

inlet duct. Determine pb for the general vicinity of the

fan. Measure td5 in Plane 5. All of these

measurements are used in the determination of

densities at the various planes of interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV) and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Motor performance data, supplied by the

motor manufacturer, are used in the determination of

motor power output for this example.

6. SEF 1 is due to the effect of insufficient length of

duct between the diffuser outlet and the elbow

downstream of the diffuser. In order to calculate the

value of SEF 1, it is necessary to measure the length

of the transition, L, and the outlet area of the diffuser,

A2.

STATIC PRESSURE TAPS

TRANSITION

DIFFUSERSECTION

INNERCYLINDER

INLETBOX

SILENCER

TEMPORARYSHORT DUCT

GUIDE VANES

SIDE VIEW L

5

2

1

PLANE 3LOCATION3

0.5 De

EXAMPLE 1C: AXIAL FORCED DRAFT FAN WITH INLET SILENCER

COMMENTS

29

7. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1

Where:

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

8. Axial fans are often rated in Fan Total Pressure.

Computation of Fan Total Pressure is illustrated in the

CALCULATIONS section of this example.

9. In order to compare the test results to the quoted

fan curve drawn for operation at 880 rpm and 0.0740

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. In this case, the test

conditions are identical to the specified conditions

and no calculations are required.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.8 in. Hg

td3 = 68°F

tw3 = 62°F

td5 = 88°F

Ps1 = -1.80 in. wg

Ps3 = -1.40 in. wg

Ps5 = 20.8 in. wg

Pv3 = 1.30 in. wg

N = 880 rpm

A1 = 170.3 ft2

A2 = 176 ft2

A3 = 170.3 ft2

A5 = A2

L = 15 ft

MEASURED MOTOR DATA

Volts = 4000, 4000, 4100

= 4033 av

Amps = 450, 445, 448

= 448 av

MOTOR NAMEPLATE DATA

4000 hp, 3 phase 60 hertz

4000 volts, 900 rpm, 520 FLA

GENERAL

Fan direct connected to motor. Motor performance

data at operating load, as supplied by motor

manufacturer: 0.88 power factor, 95% efficiency.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 68°F

tw3 = 62°F

p3 = pb + (Ps3/13.6)

= 29.8 + (-1.40/13.6)

= 29.70 in. Hg

Use Figure 20 in Annex N to obtain ρ3 = 0.0744

lbm/ft3

It is assumed that td1 = td3. The density at Plane 1:

The density at Plane 2:

FLOW RATE

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (1.3/0.0744)0.5

= 4581 fpm

Q3 = V3A3

= 4581 × 170.3

= 780144 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 780144 (0.0744/0.0743)

= 781194 cfm

ρ ρ

ρ

2 5

3

13 6

13 6

460

460

0 07442

=

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

P pp

tt

s5 b

3

d3

d5

.

.

.00 8 13 6 29 8

13 6 29 70

528

548

0 0756

. . .

. .

.

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft3

ρ ρ1 3

13 6

13 6

460

460

0 07441 8

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= −

P pp

tt

s1 b

3

d3

d1

.

.

.. ++ ×

×⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

13 6 29 8

13 6 29 70

528

528

0 0743

. .

. .

. lbm/ft3

AMCA 203-90 (R2007)

30

FAN POWER INPUT

Since the fan is direct connected to the motor, there

is no drive loss, and:

H = Hmo

= 3507 hp

SYSTEM EFFECT FACTOR

AMCA Publication 201-90, Figures 7.1, 8.1, and 8.4

indicate the following calculations:

Q2 = Q3 (ρ3/ρ2)

= 780144 (0.0744/0.0756)

= 767761 cfm

V2 = (Q2/A2)

= (767761/176)

= 4362

Duct diameter equivalent to the diffuser outlet area:

Figure 8.1 shows that for velocities over 2500 fpm,

100% effective duct length is one duct diameter for

every 1000 fpm:

= De2 (V2/1000)

= 15 (4362/1000)

= 65.43 ft.

L in % effective duct length

= (L/65.43) 100

= (15/65.43) 100

= 23%

For 23% effective duct length and a vaneaxial fan

with a 2 piece elbow, Figure 8.4 shows System EffectCurve V applies. For 4362 fpm velocity and curve V,

Figure 7.1 shows SEF 1 = 0.32 in. wg at 0.075

lbm/ft3. At 0.0756 lbm/ft3.

SEF 1 = 0.32 (0.0756/0.075)

= 0.32 in. wg

FAN STATIC PRESSURE

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

= 1.3 (170.3/170.3)2 (0.0744/0.0743)

= 1.30 in. wg

Ps2 = Ps5

= 20.8 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= 20.8 - (-1.80) - 1.30 + 0.32

= 21.62 in. wg

FAN TOTAL PRESSURE

Pt1 = Ps1 +Pv1

= -1.8 + 1.30

= -0.50 in. wg

Pv2 = Pv3 (A3/A2)2 (ρ3/ρ2)

= 1.3 (170.3/176)2 (0.0744/0.0756)

= 1.20 in. wg

Pt2 = Ps2 + Pv2

= 20.8 + 1.20

= 22.00 in. wg

Pt = Pt2 - Pt1 + SEF 1

= 22.00 - (-0.50) + 0.32

= 22.82 in. wg

Also:

Pt = Ps + Pv

Pv = Pv2

= 1.20 in. wg

Pt = 21.62 + 1.20

= 22.82 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = Q= 781194 cfm

Psc = Ps

= 21.62 in. wg

Ptc = Pt

= 22.82 in. wg

Hc = H= 3507 hp

D Ae2

ft.

=

= ×( )=

4

4 176

15

2 /

/

π

π

Hmo

volts amps power factor efficiency= × × × ×

= × × ×

3

746

3 4033 448 0 8. 88 0 95

746

3507

×

=

.

hp

AMCA 203-90 (R2007)

31

AMCA 203-90 (R2007)

1. Each of the fans, as supplied and rated by the

manufacturer, includes an outlet damper.

Performance ratings for fans with outlet dampers

cover operation with the outlet damper in the full

open position. In order to be able to compare the test

results to the fan performance ratings it is essential

that the outlet dampers be fixed in the full open

positions for the duration of the test.

2. In this example, there are no suitable locations for

traverse planes for use in determining directly the

flow rate for each fan. The alternative is to determine

the total flow rate and since the fans and their

operating speeds are alike, assume that each fan

delivers a flow rate proportional to its actual speed.

Determine Pv3 by using the root mean square of the

velocity pressure measurements made in a traverse

of Plane 3, located near the end of a straight run of

duct, such as shown in the diagram. Determine Ps3 by

averaging the static pressure measurements made in

the same traverse. Procedures for traverses are

described in Section 9.4. Ps3 is used in determining

the density at the traverse plane. Measure the area of

traverse plane, A3, which is located at the tip of the

Pitot-static tube.

3. Determine Ps2 for each fan by averaging the

pressure measurements at each of four static

pressure taps located in the short length of duct

between the outlet damper and the plenum. See

Annex E for details of static pressure taps. Measure

td2 in Plane 2 for each fan.

4. For each fan, measure td1 and tw1 in the path of the

air flowing into the fan inlet. Determine pb for the

general vicinity of the fans. Measure td3 in Plane 3. All

of these measurements are used in the determination

of densities at the various planes of interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts for each fan. Record all

pertinent motor nameplate data, including volts

(NPV) and full load amps (FLA). If the motor power

outputs are to be estimated by using the phase

current method described in Annex K, it is not

necessary to measure motor watts; however, it may

be necessary to disconnect the drives and measure

the no load amps (NLA) if the motors are not

operating at or near their full load points. Refer to

Annex K.

6. SEF 1 is due to the effect of insufficient length of

duct between the outlet of each fan and the plenum.

In this case, the duct length is so short as to be

judged equivalent to there being no duct at all. In

order to calculate the value of SEF 1, it is necessary

to measure the outlet areas of the fans, A2, and their

blast areas.

EXAMPLE 1D: CENTRIFUGAL FANS IN PARALLEL

1 1

2

3

STATIC PRESSURE TAPS

OUTLET DAMPER

SEF 1

PLENUM

SIDE VIEWPLAN VIEW

COMMENTS

32

7. The sum of the static pressure, Ps1, and the

velocity pressure, Pv1, at the inlet of a fan with an

unrestricted inlet is considered to be equal to the sum

of the static pressure, Psx, and the velocity pressure,

Pvx, at a point sufficiently distant from the inlet as to

be in still air. At this point, the static pressure is zero,

and the velocity pressure in still air is zero.

Ps1 + Pv1 = Psx + Pvx

= 0

This consideration, which is the same as that used in

the methods for testing fans for performance rating

purposes, charges to the fan losses incurred in

accelerating the air into the fan inlet and eliminates

the inaccuracies which arise in any attempt to

measure the velocity pressure and static pressure at

the fan inlet. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= Ps2 - (Ps1 + Pv1) + SEF 1

Since Ps1 + Pv1 = 0:

Ps = Ps2 + SEF 1

8. In order to compare the test results to the quoted

fan curve drawn for operation at 1900 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.05 in. Hg

td3 = 78°F

Ps3 = 5.6 in. wg

Pv3 = 0.47 in. wg

A3 = 7.4 ft2

LH Fan

td1 = 75°F

tw1 = 57°F

td2 = 79°F

Ps2 = 6.4 in. wg

N = 1910 rpm, LH fan speed

A2 = 3.2 ft2

Blast Area = 2.25 ft2

RH Fan

td1 = 75°F

tw1 = 57°F

td2 = 79°F

Ps2 = 6.4 in. wg

N = 1890 rpm, RH fan speed

A2 = 3.2 ft2

Blast Area = 2.25 ft2

MEASURED MOTOR DATA

LH Fan

Volts = 575, 572, 578

= 575 av

Amps = 16, 17, 17

= 16.7 av

NLA = 7.0

RH Fan

Volts = 575, 574, 573

= 574 av

Amps = 15, 16, 16

= 15.7 av

NLA = 7.0

MOTOR NAMEPLATE DATA

LH Fan

25 hp, 3 phase, 60 hertz

575 volts, 1780 rpm, 23 FLA

RH Fan

25 hp, 3 phase, 60 hertz

575 volts, 1780 rpm, 23 FLA

GENERAL

Outlet dampers in full open positions. Fans

connected to motors through belt drives.

CALCULATIONS

DENSITIES

For inlet conditions for both fans of:

td1 = 75°F

tw1 = 57°F

p1 = pb

= 29.05 in. Hg

Use Figure N.1 in Annex N to obtain ρ1 = 0.0718

lbm/ft3

The density at Plane 2:

AMCA 203-90 (R2007)

33

The density at Plane 3:

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.47/0.0724)0.5

= 2792 fpm

Q3 = V3A3

= 2792 × 7.4

= 20661 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 20661 (0.0724/0.0718)

= 20834 cfm

Assume that the air flow rate for each fan is

proportional to its speed.

LH Fan

Q = Q1

= 20834 [1910/(1910 + 1890)]

= 10472 cfm

RH Fan

Q = Q1

= 20834 [1890/(1910 + 1890)]

= 10362 cfm

FAN POWER INPUT

LH Fan

Measured amps/FLA = (16.7/23)

= 0.73

= 73%

RH Fan

Measured amps/FLA = (15.7/23)

= 0.68

= 68%

Annex K indicates that the average of the results of

Equation A and Equation B will provide a reasonably

accurate estimate of motor power output for a 25 hp

motor operating at approximately 70% FLA.

LH Fan

Eqn A = 25 (16.7/23) (575/575)

= 18.15 hp

Eqn B = 25 [(16.7 - 7)/(23 - 7)] (575/575)

= 15.16 hp

Hmo = (18.15 + 15.16)/2

= 16.66 hp

RH Fan

Eqn A = 25 (15.7/23) (574/575)

= 17.04 hp

Eqn B = 25 [(15.7 - 7)/(23 - 7)] (574/575)

= 13.57 hp

Hmo = (17.04 + 13.57)/2

= 15.31 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 5% for each fan.

LH Motor

HL = 0.05 Hmo

= 0.05 × 16.66

= 0.83 hp

H = Hmo - HL

= 16.66 - 0.83

= 15.83 hp

RH Motor

HL = 0.05 Hmo

= 0.05 × 15.31

= 0.77 hp

H = Hmo - HL

= 15.31 - 0.77

= 14.54 hp

SYSTEM EFFECT FACTOR

AMCA Publication 201-90, Figures 7.1 and 8.3

indicate the following calculations:

LH Fan

Q2 = Q1 (ρ1/ρ2)

= 10472 (0.0718/0.0724)

= 10385 cfm

V2 = (Q2/A2)

= (10385/3.2)

= 3245 fpm

ρ ρ2 1

1

13 6

13 6

460

460

0 07186 4

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= +

P pp

tt

s2 b d1

d2

.

.

.. 113 6 29 05

13 6 29 05

535

539

0 0724 3

. .

. .

.

××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft

ρ ρ3 1

1

13 6

13 6

460

460

0 07185 6

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= +

P pp

tt

s3 b d1

d3

.

.

.. 113 6 29 05

13 6 29 05

535

538

0 0724 3

. .

. .

.

××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft

AMCA 203-90 (R2007)

34

Blast area ratio = Blast Area/A2

= 2.25/3.2

= 0.70

RH Fan

Q2 = Q1 (ρ1/ρ2)

= 10362 (0.0718/0.0724)

= 10276 cfm

V2 = (Q2/A2)

= (10276/3.2)

= 3211 fpm

Blast area ratio = Blast Area/A2

= 2.25/3.2

= 0.70

For a blast area ratio of 0.7 and no duct, Figure 8.3

shows System Effect Curve S applies. For each fan

with velocities of 3245 fpm and 3211 fpm and curve

S, Figure 7.1 shows SEF 1 = 0.5 in. wg at 0.075

lbm/ft3. At 0.0724 lbm/ft3:

SEF 1 = 0.5 (0.0724/0.075)

= 0.48 in. wg

FAN STATIC PRESSURE

Ps = Ps2 + SEF 1

LH Fan

Ps = 6.4 + 0.48

= 6.88 in. wg

RH Fan

Ps = 6.4 + 0.48

= 6.88 in. wg

CONVERSION TO SPECIFIED CONDITIONS

LH Fan

Qc = 10472 (1900/1910)

= 10417 cfm

Psc = 6.88 (1900/1910)2 (0.075/0.0718)

= 7.11 in. wg

Hc = 15.83 (1900/1910)3 (0.075/0.0718)

= 16.28 hp

RH Fan

Qc = 10362 (1900/1890)

= 10417 cfm

Psc = 6.88 (1900/1890)2 (0.075/0.0718)

= 7.26 in. wg

Hc = 14.54 (1900/1890)3 (0.075/0.0718)

= 15.43 hp

AMCA 203-90 (R2007)

35

AMCA 203-90 (R2007)

1. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located near the end of a straight

run of duct, such as shown in the diagram. Determine

Ps3 by averaging the static pressure measurements

made in the same traverse. Procedures for traverses

are described in Section 9.4. Ps3 is used in

determining the density at the traverse plane.

Measure the area of the traverse plane, A3, which is

located at the tip of the Pitot-static tube.

2. Determine Ps1 by averaging the pressure

measurements at each of four static pressure taps in

the collar connection at the fan inlet. Determine Ps2

by averaging the pressure measurements at each of

four static pressure taps located near the fan outlet.

3. Measure td3 and tw3 in the traverse plane. Assume

td1 is equal to td3. Determine pb for the general vicinity

of the fan. Measure td2 in Plane 2. All of these

measurements are used in determining densities at

the various planes of interest.

4. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV) and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

5. SEF 1 is due to the effect of the elbow located at

the fan inlet. SEF 2 is due to the effect of insufficient

length of duct between the fan outlet and the elbow

downstream of the fan. In order to calculate the

values of the SEFs, it is necessary to measure the

inlet area and the outlet area of the fan, A1 and A2;

the length of the outlet duct, L; and the blast area of

the fan.

6. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

Where:

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

7. In order to compare the test results to the quoted

fan curve drawn for operation at 1880 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

EXAMPLE 2A: UTILITY FAN IN A VENTILATION SYSTEM

SIDE VIEW OUTLET SIDE VIEW

PLAN VIEW

STATIC PRESSURE TAPS

SEF 2L

3

1

2

3-PIECEELBOWR/D = 1

SEF 1

COMMENTS

36

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.20 in. Hg

td2 = 72°F

td3 = 72°F

tw3 = 66°F

Ps1 = -2.18 in. wg

Ps2 = 0.35 in. wg

Ps3 = -1.95 in. wg

Pv3 = 0.45 in. wg

N = 1730 rpm

A1 = 1.07 ft2

A2 = 1.17 ft2

A3 = 1.07 ft2

Blast Area = 0.7 ft2

L = 0.83 ft

MEASURED MOTOR DATA

Volts = 227, 229, 228

= 228 av

Amps = 10.2, 10.3, 10.4

= 10.3 av

NLA = 7.1

MOTOR NAMEPLATE DATA

5 hp, 3 phase, 60 hertz

230 volts, 1750 rpm, 14 FLA

GENERAL

Fan connected to motor through belt drive.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 72°F

tw3 = 66°F

p3 = pb + (Ps3/13.6)

= 29.20 + (-1.95/13.6)

= 29.06 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0719

lbm/ft3

It is assumed that td1 = td3

The density at Plane 1:

The density at Plane 2:

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.45/0.0719)0.5

= 2742 fpm

Q3 = V3A3

= 2742 × 1.07

= 2934 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 2934 (0.0719/0.0718)

= 2938 cfm

FAN POWER INPUT

Measured amps/FLA = 10.3/14

= 0.74

= 74%

Annex K indicates that the average of the results of

Equation A and Equation B will provide a reasonably

accurate estimate of motor power output for a 5 hp

motor operating at 74% FLA.

Eqn A = 5 (10.3/14) (228/230)

= 3.65 hp

Eqn B = 5 [(10.3 - 7.1)/(14 - 7.1)] (228/230)

= 2.30 hp

Hmo = (3.65 + 2.30)/2

= 2.98 hp

ρ ρ2 3

3

13 6

13 6

460

460

0 07190 35

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

P pp

tt

s2 b d3

d2

.

.

.. ++ ×

×⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

13 6 29 20

13 6 29 06

532

532

0 0723 3

. .

. .

. lbm/ft

ρ ρ1 3

3

13 6

13 6

460

460

0 07192 1

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= −

P pp

tt

s1 b d3

d1

.

.

.. 88 13 6 29 20

13 6 29 06

532

532

0 0718 3

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

. .

. .

. lbm/ft

AMCA 203-90 (R2007)

37

Figure L.1 in Annex L indicates estimated belt drive

loss of 6.5%.

HL = 0.065 Hmo

= 0.065 × 2.98

= 0.19 hp

H = Hmo - HL

= 2.98 - 0.19

= 2.79 hp

SYSTEM EFFECT FACTORS

To determine the value of SEF 1, calculate the

velocity at the fan inlet:

V1 = Q1/A1

= 2938/1.07

= 2746 fpm

AMCA Publication 201-90, Figure 9.5 indicates that

for a three piece elbow with radius to diameter ratio

of 1, and with no duct between the elbow and the fan

inlet, System Effect Curve R applies. For 2746 fpm

velocity and curve R, Figure 7.1 shows SEF 1 = 0.55

in. wg at 0.075 lbm/ft3. At 0.0718 lbm/ft3:

SEF 1 = 0.55 (0.0718/0.075)

= 0.53 in. wg

For SEF 2, AMCA Publication 201-90, Figures 7.1,

8.1, and 8.5 indicate the following calculations:

Q2 = Q3 (ρ3/ρ2)

= 2934 (0.0719/0.0723)

= 2918 cfm

V2 = (Q2/A2)

= 2918/1.17

= 2494 fpm

Duct diameter equivalent to the fan outlet area:

De2 = (4A2/π)0.5

= (4 × 1.17/π)0.5

= 1.22 ft

Figure 8.1 shows that for velocities of 2500 fpm or

less, the 100% effective outlet duct length is 2.5 duct

diameters,

= 2.5 × 1.22

= 3.05 ft

L in % effective duct length

= (L/3.05) 100

= (0.83/3.05) 100

= 27%

Blast area ratio = Blast Area/A2

= 0.7/1.17

= 0.6

For blast area ratio of 0.6, 27% effective duct length

and elbow position C, Figure 8.5 shows SystemEffect Curve P - Q applies. For 2494 fpm velocity and

curve P - Q, Figure 7.1 shows SEF 2 = 0.7 in. wg at

0.075 lbm/ft3. At 0.0723 lbm/ft3:

SEF 2 = 0.7 (0.0723/0.075)

= 0.67 in. wg

FAN STATIC PRESSURE

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

= 0.45 (1.07/1.07)2 (0.0719/0.0718)

= 0.45 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

= 0.35 - (-2.18) - 0.45 + 0.53 + 0.67

= 3.28 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 2938 (1880/1730)

= 3193 cfm

Psc = 3.28 (1880/1730)2 (0.075/0.0718)

= 4.05 in. wg

Hc = 2.79 (1880/1730)3 (0.075/0.0718)

= 3.74 hp

AMCA 203-90 (R2007)

38

AMCA 203-90 (R2007)

1. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located near the end of a straight

run of duct, such as shown in the diagram. Determine

Ps3 by averaging the static pressure measurements

made in the same traverse. Procedures for traverses

are described in Section 9.4. Ps3 is used in

determining the density at the traverse plane.

Measure the area of the traverse plane, A3, which is

located at the tip of the Pitot-static tube.

2. Determine Ps1 by using a Pitot-static tube or static

pressure taps in the duct connection at the fan inlet.

If a Pitot-static tube is used, it should not project into

the upstream elbow but be located well within the

length of the duct connection as shown in the

diagram. The friction loss in the short length of outlet

duct is assumed to be negligible, and Ps2 is

considered to be equal to the static pressure at the

duct outlet. The static pressure at the outlet of the

duct is zero gauge pressure, referred to the

atmospheric pressure in the region of the duct outlet.

In situations such as this example, the air may be

discharging from the duct into a region in which the

atmospheric pressure is somewhat different from that

to which all other pressure measurements are

referred. When this possibility exists, it is essential

that the static pressure in the region of the

discharging air be measured, referred to the same

atmospheric pressure as used in all other pressure

measurements. In this case, the pressure was

measured as 0.1 in. wg.

3. Measure td3 and tw3 in the traverse plane.

Determine pb for the general vicinity of the fan.

Measure td1 and td2. All of these measurements are

used in determining densities at the various planes of

interest.

4. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV) and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

5. SEF 1 is due to the effect of insufficient length of

duct between the fan inlet and the elbow upstream of

the fan. SEF 2 is due to the effect of insufficient

length of duct at the fan outlet. In order to calculate

the values of the SEFs, it is necessary to measure

the inlet area and the outlet area of the fan, A1 and

A2; the lengths of the inlet connection and the outlet

duct, L1 and L2; and the blast area of the fan.

EXAMPLE 2B: CENTRIFUGAL FAN IN A SAWDUST CONVEYING SYSTEM

3

12SEF 2

4-PIECE ELBOWR/D = 1

SEF 1

SIDE VIEWOUTLET SIDE VIEW

L1

L2

COMMENTS

39

6. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

Where:

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

7. In order to compare the test results to the quoted

fan curve drawn for operation at 2075 rpm and 0.075

lbm/ft3, it is necessary to convert the results to the

specified conditions. The basis for the calculations is

described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.82 in. Hg

td1 = 86.6°F

td2 = 91.3°F

tw2 = 70.4°F

td3 = 86°F

Ps1 = -11.4 in. wg

Ps2 = 0.1 in. wg

Ps3 = -8.9 in. wg

Pv3 = 1.24 in. wg

N = 2120 rpm, fan speed

A1 = 1.40 ft2

A2 = 1.40 ft2

A3 = 1.57 ft2

Blast Area = 1.26 ft2

L1 = 1.33 ft

L2 = 3.0 ft

MEASURED MOTOR DATA

Volts = 460, 460, 459

= 460 av

Amps = 26.5, 25.5, 26

= 26 av

NLA = 11.3

MOTOR NAMEPLATE DATA

30 hp, 3 phase, 60 hertz

460 volts, 1750 rpm, 36 FLA

GENERAL

Fan connected to motor through belt drive.

CALCULATION

DENSITIES

For Plane 2 conditions of:

td2 = 91.3°F

tw2 = 70.4°F

p2 = pb + (Ps2/13.6)

= 29.82 + (0.1/13.6)

= 29.83 in. Hg

Use Figure N.1 in Annex N to obtain ρ2 = 0.0714

lbm/ft3

The density at Plane 1:

The density at Plane 3:

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (1.24/0.0705)0.5

= 4596 fpm

Q3 = V3A3

= 4596 × 1.57

= 7216 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 7216 (0.0705/0.0700)

= 7268 cfm

FAN POWER INPUT

Measured amps/FLA = (26/36)

= 0.72

= 72%

ρ ρ3 2

3

13 6

13 6

460

460

0 07148 9

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= −

P pp

tt

s3 b d2

d3

.

.

.. ++ ×

×⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

13 6 29 82

13 6 29 83

551 3

546

0 0705

. .

. .

.

. lbm/ft3

ρ ρ1 2

2

13 6

13 6

460

460

0 071411

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= −

P pp

tt

s1 b d2

d1

.

.

..44 13 6 29 82

13 6 29 83

551 3

546 6

0 0700

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

. .

. .

.

.

. lbm/ft33

AMCA 203-90 (R2007)

40

Annex K indicates that the average of the results of

Equation A and Equation B will provide a reasonably

accurate estimate of motor power output for a 30 hp

motor operating at 72% FLA.

Eqn A = 30 (26/36) (460/460)

= 21.67 hp

Eqn B = 30 [(26 - 11.3)/(36 - 11.3)] (460/460)

= 17.85 hp

Hmo = (21.67 + 17.85)/2

= 19.76 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 4.8%.

HL = 0.048 Hmo

= 0.048 × 19.76

= 0.95 hp

H = Hmo - HL

= 19.76 - 0.95

= 18.81 hp

SYSTEM EFFECT FACTORS

To determine the value of SEF 1, calculate the

velocity at the fan inlet:

V1 = (Q1/A1)

= (7268/1.40)

= 5191 fpm

The diameter of the fan inlet:

D1 = (4A1/π)0.5

= (4 × 1.40/π)0.5

= 1.34 ft.

The length of the duct between the elbow and the fan

inlet in terms of D1:

= (L1/D1)

= (1.33/1.34)

= 1.0

AMCA Publication 201-90, Figure 9.5 indicates that

for a four piece elbow with a radius to diameter ratio

of 1, and with a length of duct between the elbow and

the fan inlet equal to 1 equivalent diameter, SystemEffect Curve S applies. For 5191 fpm velocity and

curve S, Figure 7.1 shows SEF 1 = 1.3 in. wg at

0.075 lbm/ft3. At 0.0700 lbm/ft3:

SEF 1 = 1.3 (0.0700/0.075)

= 1.2 in. wg

For SEF 2, AMCA Publication 201-90, Figure 8.3

indicates the following calculations:

Q2 = Q3 (ρ3/ρ2)

= 7216 (0.0705/0.0714)

= 7125 cfm

V2 = (Q2/A2)

= (7125/1.40)

= 5089 fpm

Duct diameter equivalent to the fan outlet area:

De2 = (4A2/π)0.5

= (4 × 1.40/π)0.5

= 1.34 ft

Figure 8.3 shows that for velocities over 2500 fpm,

100% effective duct length is one duct diameter per

1000 fpm:

= D2 (V2/1000)

= 1.34 (5089/1000)

= 6.82 ft

The length of the outlet duct in % effective duct

length:

= (L2/6.82) 100

= (3.0/6.82) 100

= 44%

Blast ratio area = Blast Area/A2

= 1.26/1.40

= 0.9

For blast area ratio of 0.9 and 44% effective duct

length, Figure 8.3 shows no System Effect Curveapplies and SEF 2 = 0.

FAN STATIC PRESSURE

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

= 1.24 (1.57/1.40)2 (0.0705/0.0700)

= 1.57 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

= 0.1 - (-11.4) - 1.57 + 1.2 + 0

= 11.13 in. wg

CONVERSIONS TO SPECIFIED CONDITIONS

Qc = 7268 (2075/2120)

= 7114 cfm

Psc = 11.13 (2075/2120)2 (0.075/0.0700)

= 11.42 in. wg

AMCA 203-90 (R2007)

41

Hc = 18.81 (2075/2120)2 (0.075/0.0700)

= 18.90 hp

AMCA 203-90 (R2007)

42

AMCA 203-90 (R2007)

1. This type of installation is normally classified as

one in which a satisfactory test cannot be conducted.

Due to the configurations of the airways, there are no

locations at which reasonably accurate pressure

measurements can be made. In addition, the

judgments required in determining the values of the

SEFs are susceptible to error. The purpose of

presenting this example is to illustrate the not

uncommon instance in which a test must be conducted

in order to provide performance information, even

though the results will be innaccurate to a degree

which is not normally acceptable.

2. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located as shown in the diagram.

Determine Ps3 by averaging the static pressure

measurements made in the same traverse.

Procedures for traverses are described in Section

9.4. These velocity pressure and static pressure

measurements are susceptible to error due to the

turbulence existing in the region of the fan outlet. In

addition, it is undesirable to have Plane 3 located in

a diverging airway. However, no other more suitable

location for Plane 3 exists in this example. It is

recommended that the Pitot-static tube be oriented

so that its nose is aligned with the anticipated flow

streams, particularly near the walls of the diffuser.

Determine the area of the traverse plane, A3, which is

located at the tip of the Pitot-static tube, as shown in

the diagram, not at the location of the Pitot-static tube

access holes.

3. Determine Ps4 by averaging the pressure

measurements at each of four static pressure taps

located near the fan inlet. In the same manner,

determine Ps5 at a location near the fan outlet. It is

undesirable to have pressure measurement planes

located in converging and diverging airways, but

there are no other more suitable locations for these

planes in this installation. Measure A4 and A5, the

cross-sectional areas of the airways at Planes 4 and 5.

4. Measure td3, tw3, and td4. Determine pb for the

general vicinity of the fan. These measurements are

used in the determination of densities at the various

planes of interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV) and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

EXAMPLE 2C: AXIAL FAN IN A DRYER SYSTEM

COMMENTS

4 5

1 2

STRAIGHTENING VANES

STATIC PRESSURE TAPS3

SEF 2

A3

SEF 1INNER CYLINDER

PLAN VIEW

SIDE VIEW

LOCATION OF PLANE 3

43

6. Although an elbow is located a short distance

upstream of the fan, it is considered to produce no

system effect since it is equipped with turning vanes

and the average velocity through the elbow will be

relatively low due to its large cross-sectional area.

Therefore, SEF 1 = 0. In judging SEF 2, the rapidly

diverging transition fitting downstream of the fan is

considered equivalent to no duct at the fan outlet. In

order to calculate the value of SEF2, it is necessary

to measure the outlet area of the fan, A2.

7. To calculate the Fan Static Pressure,

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

Where:

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

Ps1 and Ps2 are calculated on the basis of total

pressure considerations, using Ps4, Ps5, and the

calculated velocity pressures at Planes 1, 2, 4, and 5.

8. In order to compare the test results to the quoted

fan curve drawn for operation at 1580 rpm and

0.0690 lbm/ft3 density, it is necessary to convert the

results to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 28.90 in. Hg

td3 = 86.5°F

tw3 = 75.5°F

td4 = 85°F

Ps3 = 1.5 in. wg

Pv3 = 0.044 in. wg

Ps4 = -1.57 in. wg

Ps5 = 1.22 in. wg

N = 1590 rpm

A1 = A2 = 8.0 ft2

A3 = 29.8 ft2

A4 = 12.4 ft2

A5 = 9.6 ft2

MEASURED MOTOR DATA

Volts = 450, 449, 448

= 449 av

Amps = 25.0, 24.5, 25.0

= 24.8 av

NLA = 9.4

MOTOR NAMEPLATE DATA

25 hp, 3 phase, 60 hertz

460 volts, 1750 rpm, 31 FLA

GENERAL

Fan connected to motor through belt drive

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 86.5°F

tw3 = 75.5°F

p3 = pb + (Ps3/13.6)

= 28.90 + (1.5/13.6)

= 29.01 in. Hg

Use Figure N.1 from Annex N to obtain ρ3 = 0.0694

lbm/ft3

The density at Plane 4:

It is assumed that td1 = td4 and at the low pressure

levels which exist at Planes 1 and 4, the difference

between these pressures will be small, and assuming

ρ1 = ρ4, will result in an error which is considered

negligible. By similar reasoning, it is assumed that

ρ5 = ρ2 = ρ3.

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.044/0.0694)0.5

= 873 fpm

Q3 = V3A3

= 873 × 29.8

= 26015 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 26015 (0.0694/0.0691)

= 26128 cfm

ρ ρ4 3

3

13 6

13 6

460

460

0 06941 5

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= −

P pp

tt

s4 b d3

d4

.

.

.. 77 13 6 28 90

13 6 29 01

546 5

545

0 0691

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

. .

. .

.

. lbm/ft3

AMCA 203-90 (R2007)

44

FAN POWER INPUT

Measured amps/FLA = (24.8/31)

= 0.80

= 80%

Annex K indicates that the average of the results of

Equation A and Equation B will provide a reasonably

accurate estimate of motor power output for a 25 hp

motor operating at 80% FLA.

Eqn A = 25 (24.8/31) (449/460)

= 19.52 hp

Eqn B = 25 [(24.8 - 9.4)/(31 - 9.4)] (449/460)

= 17.40 hp

Hmo = (19.52 + 17.40)/2

= 18.46 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 4.9%.

HL = 0.049 Hmo

= 0.049 × 18.46

= 0.90 hp

H = Hmo - HL

= 18.46 - 0.90

= 17.56 hp

SYSTEM EFFECT FACTORS

SEF 1 = 0 See item 6 under COMMENTS.

To determine the value of SEF 2, AMCA Publication

201-90, Figure 8.2 indicates that a vaneaxial fan with

no outlet duct will use System Effect Curve U.

Q2 = Q3 (ρ3/ρ2)

= 26015 (0.0694/0.0694)

= 26015 cfm

V2 = (Q2/A2)

= (26015/8.0)

= 3252 fpm

From Figure 7.1, using 3252 fpm and curve U, SEF 2

= 0.26 in. wg at 0.075 lbm/ft3. At 0.0694 lbm/ft3:

SEF 2 = 0.26 (0.0694/0.075)

= 0.24 in. wg

FAN STATIC PRESSURE

Pv4 = Pv3 (A3/A4)2 (ρ3/ρ4)

= 0.044 (29.8/12.4)2 (0.0694/0.0691)

= 0.26 in. wg

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

= 0.044 (29.8/8.0)2 (0.0694/0.0691)

= 0.61 in. wg

Ps1 + Pv1 = Ps4 + Pv4

Ps1 = Ps4 + Pv4 - Pv1

= -1.57 + 0.26 - 0.61

= -1.92 in. wg

Pv5 = Pv3 (A3/A5)2 (ρ3/ρ5)

= 0.044 (29.8/9.6)2 (0.0694/0.0694)

= 0.42 in. wg

Pv2 = Pv3 (A3/A2)2 (ρ3/ρ2)

= 0.044 (29.8/8.0)2 (0.0694/0.0694)

= 0.61 in. wg

Ps2 + Pv2 = Ps5 + Pv5

Ps2 = Ps5 + Pv5 - Pv2

= 1.22 + 0.42 - 0.61

= 1.03 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

= 1.03 - (-1.92) - 0.61 + 0 + 0.24

= 2.58 in. wg

Losses between Planes 1 and 4 and between Planes

2 and 5 have been ignored.

CONVERSION TO SPECIFIED CONDITIONS

Qc = 26128 (1580/1590)

= 25964 cfm

Psc = 2.58 (1580/1590)2 (0.0690/0.0691)

= 2.54 in. wg

Hc = 17.56 (1580/1590)3 (0.0690/0.0691)

= 17.21 hp

AMCA 203-90 (R2007)

45

AMCA 203-90 (R2007)

1. This fan, as supplied and rated by the

manufacturer, includes the inlet box damper and the

inlet box. Performance ratings for fans with inlet box

dampers cover operation with the dampers in the full

open positions. In order to be able to compare the

test results to the fan performance ratings, it is

essential that the damper be fixed in the full open

position for the duration of the test.

2. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located shortly upstream of the

inlet damper. Determine Ps3 by averaging the static

pressure measurements made in the same traverse.

Procedures for traverses are described in Section

9.4. Measure A3, the area of the traverse plane,

located at the tip of the Pitot-static tube and A1, the

area of the inlet to the damper.

3. Determine Ps2 by averaging the pressure

measurements at each of four static pressure taps

located near the end of the fan outlet. See Annex E

for details of static pressure taps.

4. Measure td3 and tw3 in the traverse plane.

Determine pb for the general vicinity of the fan.

Measure td2 in Plane 2. These measurements are

used in the determination of densities at the various

planes of interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV), and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

6. SEF 1 is due to the effect of insufficient length of

duct at the fan outlet. In order to calculate the value

of SEF 1, it is necessary to measure the length of the

outlet duct, L; the fan outlet area, A2; and the blast

area of the fan.

7. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1

Since Plane 1 is located shortly downstream of Plane

3 in an airway of uniform cross-section (A1 = A3), the

conditions which exist at Plane 3 are assumed to

exist at Plane 1. Therefore, Ps1 = Ps3 and Pv1 = Pv3.

8. In order to compare the test results to the quoted

fan curve drawn for operation at 1780 rpm and 0.059

lbm/ft3 density, it is necessary to convert the results

EXAMPLE 2D: CENTRIFUGAL FAN IN A SCRUBBER SYSTEM

COMMENTS

INLET BOX

OUTLET SIDE VIEWSIDE VIEW

INLET BOX DAMPER

STATIC PRESSURE TAPS

DIFFUSER

SEF 1

31

2

L

46

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.44 in. Hg

td2 = 97°F

td3 = 63°F

tw3 = 62°F

Ps2 = 1.1 in. wg

Ps3 = -70.2 in. wg

Pv3 = 0.64 in. wg

N = 1790 rpm

A1 = 6.5 ft2

A2 = 5.32 ft2

A3 = 6.5 ft2

Blast Area = 1.89 ft2

L = 2.50 ft

MEASURED MOTOR DATA

Volts = 4160, 4150, 4150

= 4153 av

Amps = 50, 51, 52

= 51 av

NLA = 14

MOTOR NAMEPLATE DATA

500 hp, 3 phase, 60 hertz

4160 volts, 1785 rpm, 61 FLA

GENERAL

Inlet box damper in full open position. Fan direct

connected to motor.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 63°F

tw3 = 62°F

p3 = pb + (Ps3/13.6)

= 29.44 + (-70.2/13.6)

= 24.28 in. Hg

Use the modified Apjohn equation, described in

Section M.2.3 in Annex M, and the table in Figure N.2

in Annex N to calculate the density at Plane 3.

pe = 0.5603 in. Hg

pp = pe - [p3 (td3 - tw3)/2700]

= 0.5603 - [24.28 (63 - 62)/2700]

= 0.5513 in. Hg

Consider ρ1 to be equal to ρ3.

The density at Plane 2:

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.64/0.0610)0.5

= 3550 fpm

Q3 = V3A3

= 3550 × 6.5

= 23075 cfm

Q = Q1 = Q3

= 23075 cfm

FAN POWER INPUT

Measured amps/FLA = 51/61

= 0.84

= 84%

Annex K indicates that the average of the results of

Equation A and Equation B will provide a reasonably

accurate estimate of motor power output for a 500 hp

motor operating at 84% FLA.

Eqn A = 500 (51/61) (4153/4160)

= 417 hp

Eqn B = 500 [(51 - 14)/(61 - 14)] (4153/4160)

= 393 hp

Hmo = (417 + 393)/2

= 405 hp

ρ ρ2 3

3

13 6

13 6

460

460

0 06101 1

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= +

P pp

tt

s2 b d3

d2

.

.

.. 113 6 29 44

13 6 24 28

523

557

0 0696

. .

. .

.

××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft3

ρ3

31 3257 0 378

460

1 3257 24 28 0 378 0 5513

63

=−

+

=− ×( )+

. ( . )

. . . .

p pt

p

d3

4460

0 0610= . lbm/ft3

AMCA 203-90 (R2007)

47

Since the fan is direct-connected to the motor, there

is no drive loss, and:

H = Hmo

= 405 hp

SYSTEM EFFECT FACTOR

AMCA Publication 201-90, Figures 7.1 and 8.3

indicate the following calculations.

Q2 = Q3 (ρ3/ρ2)

= 23075 (0.0610/0.0696)

= 20224 cfm

V2 = Q2/A2

= 20224/5.32

= 3802 fpm

Duct diameter equivalent to the diffuser outlet area:

De2 = (4A2/π)0.5

= (4 × 5.32/π)0.5

= 2.60 ft

Figure 8.3 shows that for velocities over 2500 fpm

100% effective duct length is one duct diameter for

every 1000 fpm:

= De2 (V2/1000)

= 2.60 (3802/1000)

= 9.89 ft.

L in % effective duct length:

= (L/9.89) 100

= (2.50/9.89) 100

= 25%

Blast area ratio = Blast Area/A2

= 1.89/5.32

= 0.36

For a blast area ratio of 0.36, and 25% effective duct

length, Figure 8.3 shows System Effect Curve U

applies. For 3802 fpm velocity and curve U, Figure

7.1 shows SEF 1 = 0.36 in. wg at 0.075 lbm/ft3. At

0.0696 lbm/ft3:

SEF 1 = 0.36 (0.0696/0.075)

= 0.33 in. wg

FAN STATIC PRESSURE

Ps1 = Ps3

= - 70.2 in. wg

Pv1 = Pv3

= 0.64 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= 1.1 - (-70.2) - 0.64 + 0.33

= 71.0 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 23075 (1780/1790)

= 22946 cfm

Psc = 71.0 (1780/1790)2 (0.059/0.0610)

= 67.9 in. wg

Hc = 405 (1780/1790)3 (0.059/0.0610)

= 385 hp

AMCA 203-90 (R2007)

48

AMCA 203-90 (R2007)

1. This fan, as supplied and rated by the

manufacturer, includes the inlet box dampers and the

inlet boxes, but does not include the outlet damper.

Performance ratings for fans with inlet box dampers

cover operation with the dampers in the full open

positions. Also, performance ratings for items such as

the outlet damper are for operation in the full open

position. In order to be able to compare the test

results to the fan performance ratings, it is essential

that the outlet damper and the inlet dampers be fixed

in their full open positions.

2. Determine Pv3a and Pv3b by using the root mean

square of the velocity pressure measurements made

in Planes 3a and 3b. Determine Ps3a and Ps3b by

averaging each of the two sets of static pressure

measurements made in the same traverses.

Procedures for traverses are described in Section

9.4. Measure A3a and A3b, the areas of the traverse

planes and A1a and A1b, the areas of the inlets to the

inlet dampers.

3. Determine Ps5 by averaging the pressure

measurements of each of four static pressure taps

located downstream of the outlet damper.

4. Measure td3a, td3b, and td5. Since flue gas is being

handled by the fan, the Orsat apparatus is used by

process personnel to determine the density of the

gas. Determine pb for the general vicinity of the fan.

These data are used in the determination of densities

at the various planes of interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV) and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Motor performance data, supplied by the

motor manufacturer, are used in the determination of

motor power output for this example.

6. In this example, the duct downstream of the outlet

damper is of sufficient length, and no SEF applies.

7. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1

EXAMPLE 2E: CENTRIFUGAL FAN IN A PROCESS SYSTEM

COMMENTS

STATICPRESSURE TAPS

OUTLET DAMPER

INLET BOXES

INLET BOXDAMPERS

52

SIDE VIEW OPPOSITE OUTLET SIDE VIEW

3a 3b1a 1b

49

Ps2 is calculated on the basis of total pressure

considerations using Ps5, the outlet damper pressure

loss, and the calculated velocity pressures at Planes

2 and 5. Since the inlets to the inlet dampers (Planes

1a and 1b) are located shortly downstream of the

traverse planes (Planes 3a and 3b) in an airway of

uniform cross-section, the conditions which exist at

the traverse planes are assumed to exist at the inlets

to the inlet dampers.

Ps1 = Ps3

= (Ps3a + Ps3b)/2

Pv1 is calculated using the total flow rate and the total

area at the inlets to the inlet dampers.

Pv1 = (Q1/1096A1)2 ρ1

8. In order to compare the test results to the quoted

fan curve drawn for operation at 880 rpm and 0.049

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for calculations

is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 30.12 in. Hg

td3a = 345°F

td3b = 359°F

td5 = 363°F

Ps3a = -18.8 in. wg

Ps3b = -18.3 in. wg

Pv3a = 2.053 in. wg

Pv3b = 2.028 in. wg

Ps5 = -1.6 in. wg

N = 892 rpm

A1a = A1b

= 60.7 ft2

A2 = 115 ft2

A3a = A3b

= 60.7 ft2

A5 = 140 ft2

Blast Area = 80 ft2

The density of the gas, as determined by Orsat

analysis, is 0.0725 lbm/ft3 at 29.92 in. Hg and 70°F.

MEASURED MOTOR DATA

Volts = 4300, 4250, 4200

= 4250 av

Amps = 378, 376, 380

= 378 av

kW = 2519

MOTOR NAMEPLATE DATA

3000 hp, 3 phase, 60 hertz

4000 volts, 880 rpm, 385 FLA

GENERAL

Inlet box dampers and outlet damper in full open

positions. Fan direct connected to motor. Motor

efficiency data supplied by motor manufacturer.

Pressure loss data supplied by manufacturer of outlet

damper.

CALCULATIONS

DENSITIES

The densities at Planes 3a and 3b are:

It is assumed that ρ1a = ρ3a and ρ1b = ρ3b.

The density at Plane 5:

It is assumed that ρ2 = ρ5.

FLOW RATES

V3a = 1096 (Pv3a/ρ3a)0.5

= 1096 (2.053/0.0458)0.5

= 7338 fpm

Q3a = V3aA3a

= 7338 × 60.7

= 445417 cfm

ρ5s5 b

d5

= +×

⎛⎝⎜

⎞⎠⎟

++

⎝⎜

⎠⎟

=

0 072513 6

13 6 29 92

70 460

460

0 0

..

. .

.

P pt

77251 6 13 6 30 12

13 6 29 92

530

823

0 0468

− + ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

. . .

. .

. lbm/fft3

ρ3bs3b b

d3b

= +×

⎛⎝⎜

⎞⎠⎟

++

⎝⎜

⎠⎟

=

0 072513 6

13 6 29 92

70 460

460.

.

. .

P pt

00 072518 3 13 6 30 12

13 6 29 92

530

819

0 0451

.. . .

. .

.

− + ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= llbm/ft3

ρ3as3a b

d3a

= +×

⎛⎝⎜

⎞⎠⎟

++

⎝⎜

⎠⎟

=

0 072513 6

13 6 29 92

70 460

460.

.

. .

P pt

00 072518 8 13 6 30 12

13 6 29 92

530

805

0 0458

.. . .

. .

.

− + ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= llbm/ft3

AMCA 203-90 (R2007)

50

V3b = 1096 (Pv3b/ρ3b)0.5

= 1096 (2.028/0.0451)0.5

= 7349 fpm

Q3b = V3bA3b

= 7349 × 60.7

= 446084 cfm

Q3 = Q3a + Q3b

= 445417 + 446084

= 891501 cfm

Since the air is divided evenly between the two inlet

boxes:

ρ1 = ρ3

= (ρ3a + ρ3b)/2

= (0.0458 + 0.0451)/2

= 0.0455 lbm/ft3

Q = Q1

= Q3 (ρ3/ρ1)

= 891501 (0.0455/0.0455)

= 891501 cfm

FAN POWER INPUT

Measured amps/FLA = (378/385)

= 0.98

= 98%

Annex K indicates that Equation A will provide a

reasonably accurate estimate of motor power output

for a 3000 hp motor operating at 98% FLA.

Hmo = 3000 (378/385) (4250/4000)

= 3130 hp

The data supplied by the motor manufacturer indicate

motor efficiency of 94% at the measured power input

of 2519 kW. Using this information:

Hmo = (2519 × 0.94)/0.746

= 3174 hp

The more accurate method of estimating the motor

power output is assumed to be the latter. Since the

fan is direct connected to the motor, there is no drive

loss, and:

H = Hmo

= 3174 hp

FAN STATIC PRESSURE

Pv1 = (Q1/1096A1)2 ρ1

= (891501/1096 × 121.4)2 0.0455

= 2.04 in. wg

Pv2 = Pv1 (A1/A2)2 (ρ1/ρ2)

= 2.04 (121.4/115)2 (0.0455/0.0468)

= 2.21 in. wg

Pv5 = Pv1 (A1/A5)2 (ρ1/ρ5)

= 2.04 (121.4/140)2 (0.0455/0.0468)

= 1.49 in. wg

Ps2 + Pv2 = Ps5 + Pv5 + Damper Loss

Ps2 = Ps5 + Pv5 + Damper Loss - Pv2

= -1.6 + 1.49 + 0.75 - 2.21

= -1.57 in. wg

Ps1 = Ps3

= (Ps3a + Ps3b)/2

= (-18.8 - 18.3)/2

= -18.55 in. wg

Ps = Ps2 - Ps1 - Pv1

= -1.57 - (-18.55) - 2.04

= 14.94 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 891501 (880/892)

= 879508 cfm

Psc = 14.94 (880/892)2 (0.049/0.0455)

= 15.66 in. wg

Hc = 3174 (880/892)3 (0.049/0.0455)

= 3282 hp

AMCA 203-90 (R2007)

51

AMCA 203-90 (R2007)

1. The unusual duct arrangement in this example

makes it very difficult to obtain accurate pressure

measurements, and this fact should be understood

before testing begins. Also, the use of a diverging

inlet fitting and a converging outlet fitting with this fan

can pose additional problems. Unless the degrees of

divergence and convergence are moderate, as they

are in this example, the fan performance will be

adversely affected.

2. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located well downstream in a

straight run of duct, such as shown in the diagram.

Determine Ps3 by averaging the static pressure

measurements made in the same traverse.

Procedures for traverses are described in Section

9.4. Ps3 is used in determining the density at the

traverse plane. Measure the area of the traverse

plane, A3.

3. Determine Ps5 by averaging the pressure

measurements at each of four static pressure taps

located near the end of the duct connection at the fan

outlet. Determine Ps4 by using static pressure taps in

the duct connection at the fan inlet. Measure A4 and

A5, the cross-sectional areas of the duct connections

at the static pressure taps.

4. Measure td3 and tw3 in the traverse plane.

Determine pb for the general vicinity of the fan.

Measure td4. These measurements are used in

determining densities at the various planes of

interest.

5. Measure the fan speed, motor amps, volts, and if

possible, watts. Record all pertinent motor nameplate

data, including volts (NPV) and full load amps (FLA).

If the motor power output is to be estimated by using

the phase current method described in Annex K, it is

not necessary to measure motor watts; however, it

may be necessary to disconnect the drive and

measure the no load amps (NLA) if the motor is not

operating at or near its full load point. Motor

performance data, supplied by the motor

manufacturer, are used in the determination of motor

power output for this example.

6. SEF 1 is due to the effect of insufficient length of

duct between the fan inlet and the elbow upstream of

the fan. SEF 2 is due to the effect of insufficient

length of duct between the fan outlet and the elbow

downstream of the fan. In order to calculate the

values of the SEFs, it is necessary to measure the

inlet area and the outlet area of the fan, A1 and A2;

and the lengths of the inlet and outlet duct

connections, L1 and L2.

EXAMPLE 2F: AXIAL FAN IN A VENTILATION SYSTEM

COMMENTS

3

4 5

1 2

INNERCYLINDER

GUIDE VANES STATIC PRESSURE TAPS

SEF 1

SEF 2

2-PIECE ELBOW(TYPICAL)

L1 L2

52

7. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

Where:

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

Ps2 and Ps1 are calculated using measured static

pressure values and constant total pressure

considerations.

Ps1 + Pv1 = Ps4 + Pv4

Ps2 + Pv2 = Ps5 + Pv5

Where each velocity pressure is calculated in a

manner similar to the calculation of Pv1, shown

above.

8. In order to compare the test results to the quoted

fan curve drawn for operation at 1750 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.76 in. Hg

td3 = 82.8°F

tw3 = 57.2°F

td4 = 80°F

Ps3 = 0.5 in. wg

Pv3 = 0.783 in. wg

Ps4 = -1.1 in. wg

Ps5 = 0.82 in. wg

A1 = A2

= 7.1 ft2

A3 = A5

= 4.91 ft2

A4 = 6.2 ft2

L1 = 3.0 ft

L2 = 3.5 ft

MEASURED MOTOR DATA

Volts = 460, 461, 459

= 460 av

Amps = 25.0, 25.0, 24.8

= 24.9 av

kW = 18.0

MOTOR NAMEPLATE DATA

20 hp, 3 phase, 60 hertz

460 volts, 1760 rpm, 24.6 FLA

GENERAL

Fan direct connected to motor. Motor efficiency data

supplied by motor manufacturer. Fan speed

measurement was not obtained due to the closed

duct arrangements on both sides of the fan. The

measured amps indicate that the motor is operating

very close to the full load condition, so the rpm was

assumed to be the motor nameplate value of 1760.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 82.8°F

tw3 = 57.2°F

p3 = pb + (Ps3/13.6)

= 29.76 + (0.5/13.6)

= 29.80 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0728

lbm/ft3.

It is assumed ρ2 = ρ5 = ρ3.

The density at Planes 1 and 4:

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.783/0.0728)0.5

= 3594 fpm

Q3 = V3A3

= 3594 × 4.91

= 17647 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 17647 (0.0728/0.0729)

= 17623 cfm

ρ ρ

ρ

1 4

3

13 6

13 6

460

460

0 0728

=

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= −

P pp

tt

s4 b

3

d3

d4

.

.

.11 1 13 6 29 76

13 6 29 80

542 8

540

0 0729

. . .

. .

.

.

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft33

AMCA 203-90 (R2007)

53

FAN POWER INPUT

The data supplied by the motor manufacturer indicate

motor efficiency of 87.5% at the measured power

input of 18.0 kW. Using this information:

Hmo = (18.0 × 0.875)/0.746

= 21.1 hp

Since the fan is direct connected to the motor, there

is no drive loss, and:

H = Hmo

= 21.1 hp

SYSTEM EFFECT FACTORS

To determine the value of SEF 1, calculate the

velocity at the fan inlet:

V1 = (Q1/A1)

= (17623/7.1)

= 2482 fpm

Diameter of the fan inlet:

D1 = (4A1/π)0.5

= (4 × 7.1/π)0.5

= 3.01 ft

The length of the duct between the elbow and the fan

inlet in terms of the fan inlet diameter:

= (L1/D1)

= (3.0/3.01)

= 1.00

AMCA Publication 201-90, Figure 9.2 indicates that

for a two piece elbow with a length of duct between

the elbow and the fan inlet equal to 1.00 diameter

System Effect Curve S-T applies. For a velocity of

2482 fpm and curve S-T, Figure 7.1 shows SEF 1 =

0.25 in. wg at 0.075 lbm/ft3. At 0.0729 lbm/ft3:

SEF 1 = 0.25 (0.0729/0.075)

= 0.24 in. wg

For SEF 2, AMCA Publication 201-90, Figures 7.1,

8.1, and 8.4 indicate the following calculations:

Q2 = Q3 (ρ3/ρ2)

= 17647 (0.0728/0.0728)

= 17647 cfm

V2 = Q2/A2

= 17647/7.1

= 2485 fpm

Diameter of the fan outlet:

D2 = (4A2/π)0.5

= (4 × 7.1/π)0.5

= 3.01 ft

Figure 8.1 shows that for velocities of 2500 fpm or

less, the 100% effective duct length is 2.5 diameters:

= 2.5 × 3.01

= 7.53 ft

The length of the outlet duct in % effective duct

length:

= (L2/7.53) 100

= (3.5/7.53) 100

= 46%

From Figure 8.4, for a vaneaxial fan with a 46%

effective duct length between its discharge and a two

piece elbow, System Effect Curve W applies. From

Figure 7.1 for 2485 fpm velocity and curve W, SEF 2

is less than 0.1 in. and is considered negligible.

SEF 2 = 0.00

FAN STATIC PRESSURE

Pv5 = Pv3 (A3/A5)2 (ρ3/ρ5)

= 0.783 (4.91/4.91)2 (0.0728/0.0728)

= 0.783 in. wg

Pv2 = Pv3 (A3/A2)2 (ρ3/ρ2)

= 0.783 (4.91/7.1)2 (0.0728/0.0728)

= 0.37 in. wg

Ps2 + Pv2 = Ps5 + Pv5

Ps2 = Ps5 + Pv5 - Pv2

= 0.82 + 0.783 - 0.37

= 1.23 in. wg

Pv4 = Pv3 (A3/A4)2 (ρ3/ρ4)

= 0.783 (4.91/6.2)2 (0.0728/0.0729)

= 0.49 in. wg

Pv1 = Pv3 (A3/A1)2 (ρ3/ρ1)

= 0.783 (4.91/7.1)2 (0.0728/0.0729)

= 0.37 in. wg

Ps1 + Pv1 = Ps4 + Pv4

Ps1 = Ps4 + Pv4 - Pv1

= -1.1 + 0.49 - 0.37

= -0.98 in. wg

AMCA 203-90 (R2007)

54

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

= 1.23 - (-0.98) - 0.37 + 0.24 + 0

= 2.08 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 17623 (1750/1760)

= 17523 cfm

Psc = 2.08 (1750/1760)2 (0.075/0.0729)

= 2.12 in. wg

Hc = 21.1 (1750/1760)3 (0.075/0.0729)

= 21.3 hp

AMCA 203-90 (R2007)

55

AMCA 203-90 (R2007)

1. The two single inlet fans in this example have

been rated by the manufacturer as a two stage

assembly. Although rated as an assembly, sufficient

measurements are made to provide performance

data for each fan. The damper downstream of the

second fan is not included as part of the rated

assembly. In virtually all cases in which an air flow

control damper, such as the one shown in the

diagram, is included in the system, the point of

operation of major interest and for which the fan has

been selected is at the maximum air flow rate. This

example is no exception. Therefore, it is essential

that the damper be fixed in its full open position for

the duration of the test.

2. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3. Determine Ps3 by averaging the

static pressure measurements made in the same

traverse. Procedures for traverses are described in

Section 9.4. Ps3 is used in determining the density at

the traverse plane, A3, which is located at the tip of

the Pitot-static tube.

3. Determine the static pressures at Planes 1a, 1b-

2a, and 2b. As shown in the diagram, these planes

are located shortly downstream of the inlets and

outlets of the fans, which are the planes of interest. In

each case, the conditions which exist at the plane of

measurements are assumed to exist at the

respective plane of interest because of the close

proximity and the fact that the two planes are equal in

area. The static pressure at each plane may be

determined by averaging the static pressure

measurements at each of four static pressure taps, or

by averaging the static pressure measurements

made in a Pitot-static tube traverse of the plane.

However, due to the turbulence existing in the

regions of the outlets of the fans, it is recommended

that static pressure taps be used at Planes 1b-2a and

2b.

4. Measure td3, tw3, td1b, and td2b; td1a is assumed to be

equal to td3. Determine pb for the general vicinity of

the fan. These measurements are used in

determining densities at the planes of interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts for each fan. Record all

pertinent motor nameplate data, including volts

(NPV), and full load amps (FLA). If the motor power

outputs are to be estimated by using the phase

current method described in Annex K, it is not

necessary to measure motor watts; however, it may

be necessary to disconnect the drives and measure

the no load amps (NLA) if the motors are not

operating at or near their full load points. In this

example, a watts input measurement is made for

EXAMPLE 2G: HIGH PRESSURE CENTRIFUGAL FAN IN A SERIES

COMMENTS

3

STATIC PRESSURE TAPS

INLET BOXFAN A

INLET BOX

DAMPER

FAN B1a

1b2a

2b

SIDE VIEW

56

each motor and motor performance data, supplied by

the motor manufacturer, are used in determining

motor power outputs.

6. The SEF which would normally be attributed to

insufficient length of duct at the outlet of the first

stage fan does not apply in this case because the

fans have been rated as an assembly.

7. To calculate the static pressure for the two stage

assembly:

Ps = Ps2b - Ps1a - Pv1a

Where:

Pv1a = Pv3 (A3/A1a)2 (ρ3/ρ1a)

8. In order to compare the test results to the

performance quoted for the two stage assembly for

operation at 1780 rpm and 0.045 lbm/ft3 density, it is

necessary to convert the results to the specified

conditions. The basis for the calculations is described

in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 28.64 in. Hg

td3 = 35°F

tw3 = 33°F

td1b = td2a

= 95°F

td2b = 147°F

Pv3 = 0.745 in. wg

Ps3 = -150 in. wg

Ps1b = Ps2a

= -79.5 in. wg

Ps2b = 0.5 in. wg

Na = 1790 rpm, first stage fan speed

Nb = 1790 rpm, second stage fan speed

A1a = A2a = A1b = A2b

= 5.6 ft2

A3 = 4.92 ft2

MEASURED MOTOR DATA

First Stage

Volts = 4000, 4040, 4080

= 4040 av

Amps = 44.5, 45, 45.5

= 45 av

kW = 278

Second Stage

Volts = 4080, 4040, 4020

= 4047 av

Amps = 44, 44.5, 45

= 44.5 av

kW = 272

MOTOR NAMEPLATE DATA

Data identical for each stage:

350 hp, 3 phase, 60 hertz

4000 volts, 1790 rpm, 44.5 FLA

GENERAL

Fans direct connected to motors. Motor efficiency

data supplied by motor manufacturer.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 35°F

tw3 = 33°F

p3 = pb + (Ps3/13.6)

= 28.64 + (-150/13.6)

= 17.61 in. Hg

Use the modified Apjohn equation for partial vapor

pressure and the density equation based on perfect

gas relationships, both of which are described in

Annex M, and the data in Figure N.2 in Annex N to

calculate the density at Plane 3.

pe = 0.1879 in. Hg

Any conversion of velocity pressure to static pressure

which may occur between Planes 3 and 1a can be

ignored with no significant effect on the accuracy of

the test results. Therefore:

p p p t tp e

d3 w3

in. Hg

= − −

= − −

=

3

2700

0 187917 61 35 33

2700

0 1749

( )

.. ( )

.

ρ33

31 3257 0 378

460

1 3257 17 61 0 378 0 1749

35

=−

+

=− ×( )+

. ( . )

. . . .

p pt

p

d3

4460

0 0470 3= . lbm/ft

AMCA 203-90 (R2007)

57

AMCA 203-90 (R2007)

Ps1a = Ps3

= -150 in. wg

Assuming no change in temperature between Planes

3a and 1a:

ρ1a = ρ3

= 0.0470 lbm/ft3

To provide information regarding the flow rates

between stages and leaving the second stage,

additional density values are calculated as follows:

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.745/0.0470)0.5

= 4364 fpm

Q3 = V3A3

= 4364 × 4.92

= 21471 cfm

Q = Q1a

= Q3 (ρ3/ρ1a)

= 21471 (0.0470/0.0470)

= 21471 cfm

Q1b = Q2a

= Q3 (ρ3/ρ2a)

= 21471 (0.0470/0.0543)

= 18584 cfm

Q2b = Q3 (ρ3/ρ2b)

= 21471 (0.0470/0.0624)

= 16172 cfm

FAN POWER INPUT

At the measured power input values of 278 kW and

272 kW, the data supplied by the motor manufacturer

indicate efficiency of 95% for each motor.

Hmoa = (278 × 0.95)/0.746

= 354 hp

Hmob = (272 × 0.95)/0.746

= 346 hp

Since each fan is direct connected to its motor, there

are no drive losses and:

Ha = Hmoa

= 354 hp

Hb = Hmob

= 346 hp

FAN STATIC PRESSURE

Pv1a = Pv3 (A3/A1a)2 (ρ3/ρ1a)

= 0.745 (4.92/5.6)2 (0.0470/0.0470)

= 0.575 in. wg

The static pressure for the two stage assembly:

Ps = Ps2b - Ps1a - Pv1a

= 0.5 - (-150) - 0.575

= 149.9 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 21471 (1780/1790)

= 21351 cfm

Psc = 149.9 (1780/1790)2 (0.045/0.0470)

= 141.9 in. wg

Hac = 354 (1780/1790)3 (0.045/0.0470)

= 333 hp

Hbc = 346 (1780/1790)3 (0.045/0.0470)

= 326 hp

ρ ρ

ρ

1b 2a

s1b b d3

d4

=

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

3

3

13 6

13 6

460

460

0 04

P pp

tt

.

.

. 77079 5 13 6 28 64

13 6 17 61

495

555

0 0543

− + ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

. . .

. .

. lbm/fft

2bs2b b d3

d2b

3

3

3

13 6

13 6

460

460

0 0

ρ ρ= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

P pp

tt

.

.

. 44700 5 13 6 28 64

13 6 17 61

495

607

0 0624

. . .

. .

.

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ftt3

58

AMCA 203-90 (R2007)

1. This fan, as supplied and rated by the

manufacturer, does not include the backdraft damper.

2. Normally, velocity pressure measurements would

be made in a single plane, located in a duct common

to all branches. In this example, a measurement

plane which provides a satisfactory velocity profile

cannot be located within the short length of duct

between the point of connection of the branch ducts

and the fan inlet. The alternative, as indicated in the

diagram, is to make a velocity pressure

measurement traverse in the longest available duct

run of each branch. The velocity pressure for each

branch is determined by using the root mean square

of the velocity pressure measurements made in the

traverse. The static pressure at each traverse plane

is determined by averaging the static pressure

measurements made in the same traverse. These

static pressure values are used in determining the

densities at the traverse planes. Procedures for

traverses are described in Section 9.4. In order to

determine the air flow rates it is necessary to

measure the area of each traverse point.

3. Ps1, the static pressure at the fan inlet may be

determined by averaging the static pressure

measurements at each of four static pressure taps or

by averaging the static pressure measurements

made in a Pitot-static tube traverse of Plane 1. If a

Pitot-static tube is used, it should be positioned well

within the inlet collar in which Plane 1 is located.

Measure the area of Plane 1 for use in calculating

Pv1. The static pressure at the outlet of the backdraft

damper is zero gauge pressure, referred to the

atmospheric pressure in the region of the outlet of the

backdraft damper. In situations such as this example,

the air may be discharging from the damper into a

region in which the atmospheric pressure is

somewhat different from that to which all other

pressure measurements are referred. When this

possibility exists, it is essential that the static

pressure in the region of the discharging air be

measured, referred to the same atmospheric

pressure as used in all other pressure

measurements.

4. Measure the dry-bulb and wet-bulb temperatures

at each velocity traverse plane and the dry-bulb

temperature at Plane 1. In this example, td2 is

assumed to be equal to td1. Determine pb for the

general vicinity of the fan. These measurements are

used in determining densities at the planes of

interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV) and full load

amps (FLA). If the motor power output is to be

EXAMPLE 3A: CENTRIFUGAL FAN IN AN EXHAUST SYSTEM

COMMENTS

3a

3c

3b

1

2

SEF 1

BACKDRAFT DAMPER

AIR INTAKE VENTS

STATIC PRESSURE TAPS

PLAN VIEW

59

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

6. SEF 1 is due to the effect of there being no duct

at the fan outlet. In order to calculate the value of

SEF 1, it is necessary to measure the outlet area of

the fan, A2, and the blast area of the fan.

7. Determine the backdraft damper pressure loss by

using the performance ratings supplied by the

manufacturer and the pressure loss multiplier data in

Figure 8.7 of AMCA Publication 201-90. The use of

the multiplier is indicated because the damper is

mounted directly to the fan outlet.

8. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1

Where:

Pv1 = (Q1/1096 A1)2 ρ1

Q1 = Q3a (ρ3a/ρ1) + Q3b (ρ3b/ρ1) + Q3c (ρ3c/ρ1)

Ps2 is the sum of the static pressure in the region of

the damper outlet, which was measured as zero, and

the backdraft damper pressure loss.

9. In order to compare the test results to the quoted

fan curve drawn for operation at 810 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.8 in. Hg

td1 = 72°F

tw1 = 62°F

td3a = 77°F

tw3a = 67°F

td3b = 65°F

tw3b = 56°F

td3c = 70°F

tw3c = 62°F

Ps1 = -1.00 in. wg

Ps3a = -0.80 in. wg

Ps3b = -0.45 in. wg

Ps3c = -0.040 in. wg

Pv3a = 0.765 in. wg

Pv3b = 0.88 in. wg

Pv3c = 0.86 in. wg

N = 800 rpm

A1 = 16.8 ft2

A2 = 13.8 ft2

A3a = 5.4 ft2

A3b = A3c

= 3.0 ft2

Blast Area = 11.0 ft2

MEASURED MOTOR

Volts = 460, 458, 462

= 460 av

Amps = 28, 27, 26

= 27 av

NLA = 14.7

MOTOR NAMEPLATE DATA

25 hp, 3 phase, 60 hertz

460 volts, 1760 rpm, 32 FLA

GENERAL

Fan connected to motor through belt drive. Pressure

loss data supplied by manufacturer of backdraft

damper.

CALCULATIONS

DENSITIES

Since the static pressure values at Planes 1, 3a, 3b,

and 3c are very small, no appreciable error will occur

by using the barometric pressure instead of the

absolute pressure at each plane in the determination

of the densities. The densities at these planes are

obtained by using Figure N.1 in Annex N.

ρ1 = 0.0739 lbm/ft3

ρ3a = 0.0731 lbm/ft3

ρ3b = 0.0750 lbm/ft3

ρ3c = 0.0741 lbm/ft3

FLOW RATES

V3a = 1096 (Pv3a/ρ3a)0.5

= 1096 (0.765/0.0731)0.5

= 3546 fpm

V3b = 1096 (Pv3b/ρ3b)0.5

= 1096 (0.88/0.0750)0.5

= 3754 fpm

AMCA 203-90 (R2007)

60

V3c = 1096 (Pv3c/ρ3c)0.5

= 1096 (0.86/0.0741)0.5

= 3734 fpm

Q3a = V3aA3a

= 3546 × 5.4

= 19148 cfm

Q3b = V3bA3b

= 3754 × 3.0

= 11262 cfm

Q3c = V3cA3c

= 3734 × 3.0

= 11202 cfm

FAN POWER INPUT

Measured amps/FLA = (27/32)

= 0.84

= 84%

Annex K indicates that the average of the results of

Equation A and Equation B will provide a reasonably

accurate estimate of motor power output for a 25 hp

motor operating at 84% FLA.

Eqn A = 25 (27/32) (460/460)

= 21.1 hp

Eqn B = 25 [(27 - 14.7)/(32 - 14.7)] (460/460)

= 17.8 hp

Hmo = (21.1 + 17.8)/2

= 19.45 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 4.8%.

HL = 0.048 Hmo

= 0.048 × 19.45

= 0.93 hp

H = Hmo - HL

= 19.45 - 0.93

= 18.52 hp

SYSTEM EFFECT FACTOR

AMCA Publication 201-90, Figures 7.1 and 8.3

indicate the following calculations:

Q2 = Q1

= 41603 cfm

It is assumed that ρ2 = ρ1.

V2 = (Q2/A2)

= (41603/13.8)

= 3015 fpm

Blast area ratio = Blast area/A2

= 11.0/13.8

= 0.80

For a blast area ratio of 0.8 and no duct, Figure 8.3

shows System Effect Curve T-U applies. For 3015

fpm velocity and curve T-U, Figure 7.1 shows SEF 1

= 0.27 in. wg at 0.075 lbm/ft3 density. At 0.0739

lbm/ft3:

SEF 1 = 0.27 (0.0739/0.075)

= 0.27 in. wg

BACKDRAFT DAMPER LOSS MULTIPLIER

The data supplied by the manufacturer of the damper

indicate that the pressure loss for the damper, ΔPs, is

0.4 in. wg at the flow rate of 41603 cfm at 0.075

lbm/ft3 density. AMCA Publication 201-90, Figure 8.7

indicates a ΔPs multiplier of 1.9 for a damper which is

mounted directly to the outlet of a fan which has a

blast area ratio of 0.8.

Backdraft damper loss = ΔPs × 1.9 × (ρ2/0.075)

= 0.4 × 1.9 (0.0739/0.075)

= 0.75 in. wg

FAN STATIC PRESSURE

Pv1 = (Q1/1096 A1)2 ρ1

= [41603/(1096 × 16.8)]2 0.0739

= 0.38 in. wg

Ps2 is equal to the static pressure at the outlet of the

damper, which is zero, plus the damper loss.

Ps2 = 0 + damper loss

= 0 + 0.75

= 0.75 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= 0.75 - (-1.0) - 0.38 + 0.27

= 1.64 in. wg

Q QQ Q Qa a b b c c

== + +

=

1

3 3 1 3 3 1 3 3 1

191480 0731

0 0739

( / ) ( / ) ( / )

.

.

ρ ρ ρ ρ ρ ρ

⎛⎛⎝⎜

⎞⎠⎟

+ ⎛⎝⎜

⎞⎠⎟

+ ⎛⎝⎜

⎞⎠⎟

=

112620 0750

0 073911202

0 0741

0 0739

41

.

.

.

.

6603 cfm

AMCA 203-90 (R2007)

61

CONVERSION TO SPECIFIED CONDITIONS

Qc = 41603 (810/800)

= 42123 cfm

Psc = 1.64 (810/800)2 (0.075/0.0739)

= 1.71 in. wg

Hc = 18.52 (810/800)3 (0.075/0.0739)

= 19.51 hp

AMCA 203-90 (R2007)

62

AMCA 203-90 (R2007)

1. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located near the end of a straight

run of duct, as shown in the diagram. Determine Ps3

by averaging the static pressure measurements

made in the same traverse. Procedures for traverses

are described in Section 9.4. Ps3 is used in

determining the density at the traverse plane.

Measure the area of the traverse plane, A3, which is

located at the tip of the Pitot-static tube.

2. Determine Ps5 by averaging the pressure

measurements at each of four static pressure taps

located near the end of the duct connection at the fan

outlet. Determine Ps1 by using a Pitot-static tube or

static pressure taps in the duct connection at the fan

inlet. If a Pitot-static tube is used, it should not project

into the upstream elbow but be located well within the

length of the duct connection.

3. Measure td3 and tw3 in the traverse plane; td1 is

assumed to be equal to td3. Determine pb for the

general vicinity of the fan. Measure td5. These

measurements are used in determining densities at

the planes of interest.

4. Measure the fan speed and the motors amps,

volts, and if possible, watts. Record all pertinent

motor nameplate data, including volts (NPV), and full

load amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

5. SEF 1 is due to the effect of insufficient length of

duct between the fan inlet and the elbow upstream of

the fan. SEF 2 is due to the effect of insufficient

length of duct between the fan outlet and the elbow

downstream of the fan. In order to calculate the

values of the SEFs, it is necessary to measure the

inlet area and the outlet area of the fan, A1 and A2;

and the lengths of the inlet and outlet duct

connections, L1 and L2.

6. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

Where: Pv1 = Pv3

Since:

A1 = A3

And:

EXAMPLE 3B: AXIAL FAN IN AN EXHAUST SYSTEM

COMMENTS

3

1

2

5

SEF 1

2-PIECE ELBOW

STATICPRESSURE TAPS

PLAN VIEW

SEF 2

GUIDE VANESINNER CYLINDER

L1

L2

63

ρ1 = ρ3

Due to the close proximity of Planes 2 and 5 and the

fact that there is no change in area between the two

planes, all conditions which exist at Plane 5 are

assumed to exist at Plane 2.

Therefore:

Ps2 = Ps5

7. In order to compare the test results to the quoted

fan curve drawn for operation at 1730 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.20 in. Hg

td3 = 72°F

tw3 = 66°F

td5 = 73°F

Ps1 = -2.02 in. wg

Ps3 = -1.92 in. wg

Pv3 = 0.35 in. wg

Ps5 = 0.10 in. wg

N = 1710 rpm

A1 = A2 = A3 = A5

= 2.64 ft2

L1 = 1.5 ft, length of inlet duct

L2 = 2.25 ft, length of the outlet duct

MEASURED MOTOR DATA

Volts = 227, 229, 228

= 228 av

Amps = 12.2, 12.3, 12.4

= 12.3 av

NLA = 7

MOTOR NAMEPLATE DATA

5 hp, 3 phase, 60 hertz

230 volts, 1760 rpm, 14.0 FLA

GENERAL

Fan connected to motor through belt drive.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 72°F

tw3 = 66°F

p3 = pb + (Ps3/13.6)

= 29.20 + (-1.92/13.6)

= 29.06 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0719

lbm/ft3.

Assume that td1 = td3.

Assume that td2 = td5 and Ps2 = Ps5.

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.35/0.0719)0.5

= 2418 fpm

Q3 = V3A3

= 2418 × 2.64

= 6384 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 6384 (0.0719/0.0719)

= 6384 cfm

Q2 = Q5

= Q3 (ρ3/ρ5)

= 6384 (0.0719/0.0721)

= 6366 cfm

ρ ρ

ρ

2

s5 b

3

d3

d5

=

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

5

3

13 6

13 6

460

460

0 07190

P pp

tt

.

.

... . .

. .

.

10 13 6 29 20

13 6 29 06

532

533

0 0721

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft3

ρ ρ1s1 b

3

d3

d1

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= −

3

13 6

13 6

460

460

0 07192 0

P pp

tt

.

.

.. 22 13 6 29 20

13 6 29 06

532

532

0 0719

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

. .

. .

. lbm/ft3

AMCA 203-90 (R2007)

64

FAN POWER INPUT

Measured amps/FLA = (12.3/14.0)

= 0.88

= 88%

Annex K indicates that the average of the results of

Equation A and Equation B will provide a reasonably

accurate estimate of motor power output for a 5 hp

motor operating at 88% FLA.

Eqn A = 5 (12.3/14) (228/230)

= 4.35 hp

Eqn B = 5 [(12.3 - 7)/(14 - 7)] (228/230)

= 3.75 hp

Hmo = (4.35 + 3.75)/2

= 4.05 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 6.3%.

HL = 0.063 Hmo

= 0.063 × 4.05

= 0.26 hp

H = Hmo - HL

= 4.05 - 0.26

= 3.79 hp

SYSTEM EFFECT FACTORS

To determine the value of SEF 1, calculate the

velocity at the fan inlet:

V1 = (Q1/A1)

= (6384/2.64)

= 2418 fpm

Calculate the diameter of the fan inlet:

D1 = (4A1/π)0.5

= (4 × 2.64/π)0.5

= 1.83 ft.

Calculate the length of duct between the elbow and

the fan inlet in terms of the fan inlet diameter:

= (L1/D1)

= (1.5/1.83)

= 0.82

AMCA Publication 201-90, Figure 9.2, indicates that

for a vaneaxial fan with a two piece elbow with a

length of duct between the elbow and the fan inlet

equal to 0.8 diameters, System Effect Curve R-S

(estimated) applies. For 2418 fpm velocity and curve

R-S, Figure 7.1 shows SEF 1 = 0.24 in. wg at 0.075

lbm/ft3 density. At 0.0719 lbm/ft3:

SEF 1 = 0.24 (0.0719/0.075)

= 0.23 in. wg

For SEF 2, AMCA Publication 201-90, Figures 7.1,

8.1, and 8.4 indicate the following calculations:

V2 = (Q2/A2)

= (6366/2.64)

= 2411 fpm

The diameter of the fan outlet:

D2 = (4A2/π)0.5

= (4 × 2.64/π)0.5

= 1.83 ft

Figure 8.1 shows that for velocities of 2500 fpm or

less, the 100% effective duct length is 2.5 diameters:

= 2.5 × 1.83

= 4.58 ft

The length of the outlet duct in % effective duct

length:

= (L2/4.58) 100

= (2.25/4.58) 100

= 49%

From Figure 8.4, for a vaneaxial fan with a 49%

effective duct length between its discharge and a two

piece elbow, System Effect Curve W applies. From

Figure 7.1, for 2411 fpm velocity and curve W, SEF 2

is less than 0.1 in. wg, and is considered negligible.

SEF 2 = 0.00

FAN STATIC PRESSURE

Since:

A1 = A3

ρ1 = ρ3

Pv1 = Pv3

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

= 0.10 - (-2.02) - 0.35 + 0.23 + 0.00

= 2.00 in. wg

AMCA 203-90 (R2007)

65

CONVERSION TO SPECIFIED CONDITIONS

Qc = 6384 (1730/1710)

= 6459 cfm

Psc = 2.00 (1730/1710)2 (0.075/0.0719)

= 2.14 in. wg

Hc = 3.79 (1730/1710)3 (0.075/0.0719)

= 4.09 hp

AMCA 203-90 (R2007)

66

AMCA 203-90 (R2007)

1. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located in the duct connection at

the fan inlet, as shown in the diagram. Determine Ps3

by averaging the static pressure measurements

made in the same traverse. Procedures for traverses

are described in Section 9.4. Ps3 is used in

determining the density at the traverse plane.

Measure the area of the traverse plane, A3, which is

located at the tip of the Pitot-static tube. In locating

Plane 3 downstream of the scrubber, changes in the

composition of the air as a result of the action of the

scrubber are properly taken into account in the

determination of fan air flow rate. Due to the close

proximity of Planes 1 and 3, and the fact that there is

no change in area between the two planes, the

conditions which exist at Plane 3 are assumed to

exist at Plane 1.

2. Ps2, the static pressure at the fan outlet, is zero.

3. Measure td3 and tw3 in the traverse plane.

Determine pb for the general vicinity of the fan.

Measure td2. These measurements are used in

determining densities at the planes of interest.

4. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV), and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

5. SEF 1 is due to the effect of there being no duct

at the fan outlet. In order to calculate the value of

SEF 1, it is necessary to measure the outlet area of

the fan, A2, and the blast area of the fan.

6. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1

Where:

Pv1 = Pv3

Ps1 = Ps3

Ps2 = 0

7. In order to compare the test results to the quoted

fan curve drawn for operation at 1700 rpm and 0.071

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

COMMENTS

WET CELL SCRUBBER

SEF 1 PLAN VIEW

SIDE VIEW

3

1

2

EXAMPLE 3C: CENTRIFUGAL FAN IN A SCRUBBER SYSTEM

67

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.80 in. Hg

td3 = 65°F

tw3 = 64°F

td2 = 70°F

Ps3 = -8.0 in. wg

Pv3 = 0.337 in. wg

N = 1672 rpm

A1 = A3

= 7.06 ft2

A2 = 5.15 ft2

Blast Area = 3.67 ft2

MEASURED MOTOR DATA

Volts = 450, 458, 462

= 457 av

Amps = 44, 45, 44.5

= 44.5 av

MOTOR NAMEPLATE DATA

40 hp, 3 phase, 60 hertz

460 volts, 1780 rpm, 49 FLA

GENERAL

Fan connected to motor through belt drive.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 65°F

tw3 = 64°F

p3 = pb + (Ps3/13.6)

= 29.80 + (-8.0/13.6)

= 29.21 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0732

lbm/ft3.

It is assumed that:

td1 = td3

Ps1 = Ps3

ρ1 = ρ3

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.337/0.0732)0.5

= 2352 fpm

Q3 = V3A3

= 2353 × 7.06

= 16605 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 16605 (0.0732/0.0732)

= 16605 cfm

Q2 = Q3 (ρ3/ρ2)

= 16605 (0.0732/0.0740)

= 16425 cfm

FAN POWER INPUT

Measured amps/FLA = (44.5/49)

= 0.91

= 91%

Annex K indicates that Equation A will provide a

reasonably accurate estimate of motor power output

for a 40 hp motor operating at 91% FLA.

Hmo = 40 (44.5/49) (457/460)

= 36.1 hp

Figure L.1 in Annex L indicates estimate belt drive

loss of 4.5%.

HL = 0.045 Hmo

= 0.045 × 36.1

= 1.6 hp

H = Hmo - HL

= 36.1 - 1.6

= 34.5 hp

SYSTEM EFFECT FACTOR

AMCA Publication 201-90, Figures 7.1 and 8.3,

indicate the following calculations:

ρ ρ2s2 b

3

d3

d2

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= +

3

13 6

13 6

460

460

0 07320 13

P pp

tt

.

.

... .

. .

.

6 29 80

13 6 29 21

525

530

0 0740

××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft3

AMCA 203-90 (R2007)

68

V2 = (Q2/A2)

= (16425/5.15)

= 3189 fpm

Blast area ratio = Blast area/A2

= 3.67/5.15

= 0.71

For a blast area ratio of 0.7 and no duct, Figure 8.3

shows System Effect Curve S applies. For 3189 fpm

velocity and curve S, Figure 7.1 shows SEF 1 = 0.5

in. wg at 0.075 lbm/ft3 density. At 0.0740 lbm/ft3:

SEF 1 = 0.5 (0.074/0.075)

= 0.49 in. wg

FAN STATIC PRESSURE

Pv1 = Pv3

= 0.337 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= 0 - (-8.0) - 0.337 + 0.49

= 8.15 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 16605 (1700/1672)

= 16883 cfm

Psc = 8.15 (1700/1672)2 (0.071/0.0732)

= 8.17 in. wg

Hc = 34.5 (1700/1672)3 (0.071/0.0732)

= 35.2 hp

AMCA 203-90 (R2007)

69

AMCA 203-90 (R2007)

1. This centrifugal roof ventilator, as supplied and

rated by the manufacturer, does not include the

backdraft damper. It is essential that the backdraft

damper blades be fixed in their full open positions,

otherwise uneven velocity distribution will occur at

the inlet to the ventilator, adversely affecting its

performance.

2. Normally, velocity pressure measurements would

be made in a single plane, located in a duct common

to all branches. In this example, a measurement

plane which provides a satisfactory velocity profile

cannot be located within the short length of duct

between the point of connection of the branch ducts

and the ventilator inlet. The alternative, as indicated

in the diagram, is to make a velocity pressure

measurement traverse in each branch. The velocity

pressure for each branch is determined by using the

root mean square of the velocity pressure

measurements made in the traverse. The static

pressure at each traverse plane is determined by

averaging the static pressure measurements made in

the same traverse. These static pressure values are

used in determining the densities at the traverse

planes. Procedures for traverses are described in

Section 9.4. In order to determine the air flow rates, it

is necessary to measure the area of each traverse

plane.

3. Ps4 may be determined by averaging the static

pressure measurements at each of four static

pressure taps or by averaging the static pressure

measurements made in a Pitot-static tube traverse of

Plane 4. If a Pitot-static tube is used, it should be

positioned well within the duct in which Plane 4 is

located, and not project into the upstream elbows.

Measure the area of Plane 1 for use in calculating

Pv1. In this example, A4 = A1. Ps2, the static pressure

at the outlet of the ventilator, is zero gauge pressure,

referred to the atmospheric pressure in the region of

the ventilator outlet. In situations such as this

example, the air may be discharging from the

ventilator into a region in which the atmospheric

pressure is somewhat different from that to which all

other pressure measurements are referred. When

this possibility exists, it is essential that the static

pressure in the region of the discharging air be

measured, referred to the same atmospheric

pressure as used in all other pressure

measurements. In this case, Ps2 was measured as

zero.

4. Measure the dry-bulb and wet-bulb temperatures

at each velocity traverse plane. In this example, td1

and td4 are assumed to be equal to td3a. Determine pb

for the general vicinity of the fan. These

measurements are used in determining densities at

the planes of interest.

COMMENTS

BACKDRAFT DAMPER

STATIC PRESSURE TAPS

3a 3b

2

1

4

SIDE VIEW

EXAMPLE 3D: CENTRIFUGAL ROOF VENTILATOR WITH DUCTED INLET

70

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV) and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

6. Determine the backdraft damper pressure loss by

using the performance ratings supplied by the

manufacturer.

7. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1

Where:

Pv1 = (Q1/1096 A1)2 ρ1

Q1 = Q3a (ρ3a/ρ1) + Q3b (ρ3b/ρ1)

Ps1 = Ps4 - backdraft damper pressure loss

Ps2 = 0

8. In order to compare the test results to the quoted

fan curve drawn for operation at 620 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.20 in. Hg

td3a = td3b

= 72°F

tw3a = tw3b

= 66°F

Ps2 = 0 in. wg

Ps4 = -0.88 in. wg

Ps3a = Ps3b

= -0.85 in. wg

Pv3a = 0.27 in. wg

Pv3b = 0.275 in. wg

N = 625 rpm

A1 = A4

= 7.9 ft2

A3a = 3.4 ft2

A3b = 3.3 ft2

MEASURED MOTOR DATA

Volts = 450, 455, 460

= 455 av

Amps = 5.7, 5.85, 5.9

= 5.82 av

MOTOR NAMEPLATE DATA

5 hp, 3 phase, 60 hertz

460 volts, 1780 rpm, 5.95 FLA

GENERAL

Fan connected to motor through belt drive. Pressure

loss data supplied by manufacturer of backdraft

damper.

CALCULATIONS

DENSITIES

For Planes 3a and 3b conditions of:

td3a = td3b

= 72°F

tw3a = tw3b

= 66°F

p3a = p3b

= pb + (Ps3a/13.6)

= 29.20 + (-0.85/13.6)

= 29.14 in. Hg

Use Figure N.1 in Annex N to obtain:

ρ3a = ρ3b

= 0.0721 lbm/ft3

It is assumed that:

td1 = td4 = td3a = td3b

Since the differences in the static pressures at

Planes 1, 3a, and 4 are very small, no appreciable

error will occur by assuming:

ρ1 = ρ4 = ρ3a = ρ3b

FLOW RATES

V3a = 1096 (Pv3a/ρ3a)0.5

= 1096 (0.27/0.0721)0.5

= 2121 fpm

AMCA 203-90 (R2007)

71

V3b = 1096 (Pv3b/ρ3b)0.5

= 1096 (0.275/0.0721)0.5

= 2140 fpm

Q3a = V3aA3a

= 2121 × 3.4

= 7211 cfm

Q3b = V3bA3b

= 2140 × 3.3

= 7062 cfm

Q = Q1

= Q3a (ρ3a/ρ1) + Q3b (ρ3b/ρ1)

= 7211 (0.0721/0.0721) + 7062 (0.0721/0.0721)

= 14273 cfm

FAN POWER INPUT

Measured amps/FLA = (5.82/5.95)

= 0.98

= 98%

Annex K indicates that Equation A will provide a

reasonably accurate estimate of motor power output

for a 5 hp motor operating at 98% FLA.

Hmo = 5 (5.82/5.95) (455/460)

= 4.84 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 5.8%.

HL = 0.058 Hmo

= 0.058 × 4.84

= 0.28 hp

H = Hmo - HL

= 4.84 - 0.28

= 4.56 hp

BACKDRAFT DAMPER LOSS

The data supplied by the manufacturer of the damper

indicate that the pressure loss for the damper, ΔPs, is

0.22 in. wg at the flow rate of 14273 cfm at 0.075

lbm/ft3 density.

Backdraft damper loss = ΔPs (ρ4/0.075)

= 0.22 (0.0721/0.075)

= 0.21 in. wg

FAN STATIC PRESSURE

Pv1 = (Q1/1096 A1)2 ρ1

= [14273/(1096 × 7.9)]2 0.0721

= 0.20 in. wg

Ps1 = Ps4 - damper loss

= -0.88 - 0.21

= -1.09 in. wg

Ps = Ps2 - Ps1 - Pv1

= 0 - (-1.09) - 0.20

= 0.89 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 14273 (620/625)

= 14159 cfm

Psc = 0.89 (620/625)2 (0.075/0.0721)

= 0.91 in. wg

Hc = 4.56 (620/625)3 (0.075/0.0721)

= 4.63 hp

AMCA 203-90 (R2007)

72

AMCA 203-90 (R2007)

1. This is an air conditioning unit which has been

assembled at the installation site. The subject of the

test is the fan, which is rated by the manufacturer as

free-standing, unencumbered by the cabinet in which

it has been installed. The fan performance ratings are

based on operation with the fan outlet ducted. Before

proceeding with the test, it is essential that all

dampers--outside air, return air, mixing box,

multizone, face and bypass or volume control--be

fixed in the positions agreed upon by all interested

parties as being applicable for the installation. Also,

the temperatures of the heating coils must be kept

constant throughout the test period. It may be

necessary to lock out, disconnect, or otherwise

modify automatic control devices in order to prevent

the positions of the dampers and temperatures of the

coils from changing during the test. Refer to Section

17.4.3 for additional considerations affecting the test

procedure for fans in this type of installation.

2. Normally, velocity pressure measurements would

be made in a single plane, located in a duct common

to all branches. In this example, a measurement

plane which provides a satisfactory velocity profile

cannot be located upstream of the fan or between the

point of connection of the branch ducts and the fan

outlet. The alternative, as indicated in the diagram, is

to make a velocity pressure measurement traverse in

each branch. The velocity pressure for each branch

is determined by using the root mean square of the

velocity pressure measurements made in the

traverse. the static pressure at each traverse plane is

determined by averaging the static pressure

measurements made in the same traverse. These

static pressure values are used in determining the

densities at the traverse planes. Procedures for

traverses are described in Section 9.4. In order to

determine the air flow rates, it is necessary to

measure the area of each traverse plane.

3. Determine Ps4 by averaging the static pressure

measurements made in a traverse of Plane 4.

Determine Ps5 in a similar manner. Pitot-static tube

traverses are used in determining these static

pressures because the installation of suitable

pressure taps is usually prevented by the insulating

material encountered in this type of equipment. Due

to the abrupt expansion in area from Plane 2 to Plane

5, it is assumed that there is no conversion of velocity

pressure at Plane 2 to static pressure at Plane 5.

Therefore, it is assumed that Ps2 = Ps5. Measure the

area of Plane 4 for use in calculating Pv4.

4. Measure the dry-bulb and wet-bulb temperatures

at Plane 4 and the dry-bulb temperatures at Planes

3a, 3b, and 5. Determine pb for the general vicinity of

the air conditioning unit. These measurements are

used in determining densities at the planes of interest.

COMMENTS

4

2

5SEF 1

SEF 2

SPRAYSECTION FAN SECTION

REHEAT COILDIFFUSERPLATE

PREHEAT COILSFILTER SECTION

RETURNAIR

OUTSIDEAIR

3a

3b

L

+

+

+

++

+

+

+

+

+

PLAN VIEW

SIDE VIEW

EXAMPLE 4A: CENTRIFUGAL FAN IN A BUILT-UP AIR CONDITIONING UNIT

73

5. Measure the fan speed and motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV), and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

6. SEF 1 is due to the effect of insufficient distance

between the fan inlets and the side walls of the fan

cabinet. SEF 2 is attributed to the high degree of

divergence of the transition fitting at the fan outlet.

The effect created by this fitting is considered to be

equivalent to the effect created by having no duct at

the fan outlet. In order to determine the values of the

SEFs, it is necessary to measure the diameter of an

inlet of the fan, the distance between a fan inlet and

a side wall of the fan cabinet, and the outlet area and

blast area of the fan.

7. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

= Ps2 - (Ps1 + Pv1) + SEF 1 + SEF 2

Where:

Ps2 = Ps5

Ps1 + Pv1 = Ps4 + Pv4

Pv4 = (Q4/1096 A4)2 ρ4

Q4 = Q1

= Q3a (ρ3a/ρ1) + Q3b (ρ3b/ρ1)

The calculation of Pv4 is often ignored in instances

similar to this example on the basis that the

calculated value of Pv4 is relatively small and its

omission does not affect the test results significantly.

8. In order to compare the test results to the quoted

fan curve drawn for operation at 1170 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 28.72 in. Hg

td3a = 59°F

td3b = 90°F

td4 = 56°F

td5 = 58°F

Ps4 = -1.75 in. wg

Ps3a = 3.65 in. wg

Ps3b = 3.45 in. wg

Pv3a = 0.60 in. wg

Pv3b = 0.47 in. wg

Ps5 = 3.77 in. wg

N = 1160 rpm

A2 = 18.9 ft2

A3a = 7.2 ft2

A3b = 9.7 ft2

A4 = 93.2 ft2

Blast Area = 13.3 ft2

D1 = 3.92 ft, fan inlet diameter

L = 2.83 ft

MEASURED MOTOR DATA

Volts = 462, 465, 465

= 464 av

Amps = 82, 81, 83

= 82 av

MOTOR NAMEPLATE DATA

75 hp, 3 phase, 60 hertz

460 volts, 1780 rpm, 90.3 FLA

GENERAL

Fan connected to motor through belt drive.

CALCULATIONS

DENSITIES

For Plane 4 conditions of:

td4 = 56°F

tw4 = 54°F

p4 = pb + (Ps4/13.6)

= 28.72 + (-1.75/13.6)

= 28.59 in. Hg

AMCA 203-90 (R2007)

74

Use Figure N.1 in Annex N to obtain ρ4 = 0.0731

lbm/ft3.

It is assumed that ρ1 = ρ4.

FLOW RATES

V3a = 1096 (Pv3a/ρ3a)0.5

= 1096 (0.60/0.0737)0.5

= 3127 fpm

V3b = 1096 (Pv3b/ρ3b)0.5

= 1096 (0.47/0.0695)0.5

= 2850 fpm

Q3a = V3aA3a

= 3127 × 7.2

= 22514 cfm

Q3b = V3bA3b

= 2850 × 9.7

= 27645 cfm

Q = Q1

= Q3a (ρ3a/ρ1) + Q3b (ρ3b/ρ1)

= 22514 (0.0737/0.0731) + 27645 (0.0695/0.0731)

= 48982 cfm

Q2 = Q1 (ρ1/ρ2)

= 48982 (0.0731/0.0739)

= 48452 cfm

FAN POWER INPUT

Measured amps/FLA = (82/90.3)

= 0.91

= 91%

Annex K indicates that Equation A will provide a

reasonably accurate estimate of motor power output

for a 75 hp motor operating at 91% FLA.

Hmo = 75 (82/90.3) (464/460)

= 68.7 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 4.3%.

HL = 0.043 Hmo

= 0.043 × 68.7

= 2.95 hp

H = Hmo - HL

= 68.7 - 2.95

= 68.75 hp

SYSTEM EFFECT FACTORS

SEF 1 is due to the effect of insufficient distance

between the fan inlets and the side walls of the fan

plenum. The distance is 2.83 ft, or:

(2.83/3.92) = 0.72

= 72%

Of the fan inlet diameter. The area of the fan inlets:

A1 = 2 (π D12/4)

= 2 (π × 3.922/4)

= 24.1 ft2

The fan inlet velocity:

V1 = (Q1/A1)

= (48982/24.1)

= 2032 fpm

AMCA Publication 201-90, Figure 9.11A, indicates

that for a plenum wall spacing of 72% of the fan inlet

diameter System Effect Curve V applies. For 2032

fpm inlet velocity and curve V, Figure 7.1 shows SEF

1 = 0.06 in. wg at 0.075 lbm/ft3 density. At 0.0731

lbm/ft3:

SEF 1 = 0.06 (0.0731/0.075)

= 0.06 in. wg

For SEF 2, AMCA Publication 201-90, Figures 7.1

and 8.3, indicate the following calculations:

ρ ρ5 4

4

13 6

13 6

460

460

0 07313 77

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

P pp

tt

s5 b d4

d5

.

.

.. ++ ×

×⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

13 6 28 72

13 6 28 59

516

518

0 0739

. .

. .

. lbm/ft3

ρ ρ3bs3b b d4

d3b

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

4

4

13 6

13 6

460

460

0 07313

P pp

tt

.

.

... . .

. .

.

45 13 6 28 72

13 6 28 59

516

550

0 0695

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft3

ρ ρ3as3a b d4

d3a

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

4

4

13 6

13 6

460

460

0 07313

P pp

tt

.

.

... . .

. .

.

65 13 6 28 72

13 6 28 59

516

519

0 0737

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft3

AMCA 203-90 (R2007)

75

V2 = (Q2/A2)

= (48452/18.9)

= 2564 fpm

Blast area ratio = Blast Area/A2

= 13.3/18.9

= 0.70

For a blast area ratio of 0.7 and no duct, Figure 8.3

shows System Effect Curve S applies. For 2564 fpm

velocity and curve S, Figure 7.1 shows SEF 2 = 0.33

in. wg at 0.075 lbm/ft3 density. At 0.0739 lbm/ft3:

SEF 2 = 0.33 (0.0739/0.075)

= 0.33 in. wg

FAN STATIC PRESSURE

Pv4 = (Q4/1096 A4)2 ρ4

Since:

ρ4 = ρ1

Q4 = Q1

Pv4 = (48982/1096 × 93.2)2 0.0731

= 0.02 in. wg

Ps1 + Pv1 = Ps4 + Pv4

= -1.75 + 0.02

= -1.73 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1 + SEF 2

= Ps2 - (Ps1 + Pv1) + SEF 1 + SEF 2

= 3.77 - (-1.73) + 0.06 + 0.33

= 5.89 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 48982 (1170/1160)

= 49404 cfm

Psc = 5.89 (1170/1160)2 (0.075/0.0731)

= 6.15 in. wg

Hc = 65.75 (1170/1160)3 (0.075/0.0731)

= 69.22 hp

AMCA 203-90 (R2007)

76

AMCA 203-90 (R2007)

1. This is a factory assembled, draw-through central

station unit. The subject of the test is the fan section,

which is rated by the manufacturer as an assembly of

the fan and the cabinet in which the fan has been

installed. As a draw-through unit, the performance

ratings for the fan section are based on operation

with the fan outlet ducted. Before proceeding with the

test, it is essential that all dampers--outside air, return

air, mixing box, multizone, face and bypass, or

volume control--be fixed in the positions agreed upon

by all interested parties as being applicable for the

installation. Also, the temperatures of heating and

cooling coils must be kept constant throughout the

test period. It may be necessary to lock out,

disconnect, or otherwise modify automatic control

devices in order to prevent the positions of the

dampers and temperatures of the coils from changing

during the test. Refer to Section 17.4.2 for additional

considerations affecting the test procedure in this

type of installation.

2. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located near the end of a straight

run of duct, as shown in the diagram. Determine Ps3

by averaging the static pressure measurements

made in the same traverse. This static pressure value

is used to determine the density at the traverse

plane. Procedures for traverses are described in

Section 9.4. In order to determine the air flow rate, it

is necessary to measure the area of the traverse

plane.

3. Determine Ps1 by averaging the static pressure

measurements made in a traverse of Plane 1. Ps5

may be determined in a similar manner or by

averaging the pressure measurements at each of

four static pressure taps. If it is possible to install

suitable pressure taps, their use is preferred in the

region of the fan outlet. due to the close proximity of

Planes 2 and 5, and the fact that there is no change

in area between the two planes, the conditions which

exist at Plane 5 are assumed to exist at Plane 2.

Measure the area of Plane 1 for use in calculating

Pv1.

4. Measure the dry-bulb and wet-bulb temperatures

at Plane 3 and the dry-bulb temperatures at Planes 1

and 5. Determine pb for the general vicinity of the air

conditioning unit. These measurements are used to

determine densities at the planes of interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV), and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

COMMENTS

1

PLAN VIEWRETURN AIRSTATIC PRESSURE TAPS

SEF 1

OUTSIDEAIR

FILTER SECTION COIL SECTION

FAN SECTION

3

25

L

SIDE VIEW

+

+ +

+

EXAMPLE 4B: CENTRAL STATION AIR CONDITIONING UNIT, FACTORY ASSEMBLED DRAW-

THROUGH TYPE

77

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

6. SEF 1 is due to the effect of insufficient length of

duct between the fan outlet and the elbow

downstream of the fan. In order to determine the

value of SEF 1, it is necessary to measure the outlet

area of the fan, A2; the length of the outlet duct, L;

and the blast area of the fan.

7. To calculate the Fan Section Static Pressure:

Ps = Ps2 - Ps1 - Pv1 + SEF 1

Where:

Ps2 = Ps5

Pv1 = (Q1/1096A1)2 ρ1

The calculation of Pv1 is often ignored in instances

similar to this example on the basis that the

calculated value of Pv1 is relatively small, and it

omission does not affect the test results significantly.

8. In order to compare the test results to the quoted

fan section curve drawn for operation at 1430 rpm

and 0.075 lbm/ft3 density, it is necessary to convert

the results to the specified conditions. The basis for

the calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.27 in. Hg

td1 = 47.5°F

td3 = 49.3°F

tw3 = 47.3°F

td5 = 49°F

Ps1 = -0.847 in. wg

Ps3 = 1.31 in. wg

Pv3 = 0.294 in. wg

Ps5 = 1.39 in. wg

N = 1402 rpm

A1 = 147.2 ft2

A2 = A3 = A5

= 15.42 ft2

Blast Area = 9.4 ft2

L = 2.0 ft, length of outlet duct

MEASURED MOTOR DATA

Volts = 440, 444, 442

= 442 av

Amps = 47.4, 47.7, 48.0

= 47.7 av

MOTOR NAMEPLATE DATA

40 hp, 3 phase, 60 hertz

440 volts, 1770 rpm, 49.7 FLA

GENERAL

Fan connected to motor through belt drive.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 49.3°F

tw3 = 47.3°F

p3 = pb + (Ps3/13.6)

= 29.27 + (1.31/13.6)

= 29.37 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0762

lbm/ft3.

It is assumed ρ2 = ρ5.

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.294/0.0762)0.5

= 2153 fpm

ρ ρ5 3

13 6

13 6

460

460

0 07621 39

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

P pp

tt

s5 b

3

d3

d5

.

.

.. ++ ×

×⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

13 6 29 27

13 6 29 37

509 3

509

0 0763

. .

. .

.

. lbm/ft3

ρ ρ1 3

13 6

13 6

460

460

0 07620 8

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

= −

P pp

tt

s1 b

3

d3

d1

.

.

.. 447 13 6 29 27

13 6 29 37

509 3

507 5

0 0760

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

. .

. .

.

.

. lbm/ftt3

AMCA 203-90 (R2007)

78

Q3 = V3A3

= 2153 × 15.42

= 33199 cfm

Q = Q1

= Q3 (ρ3/ρ1)

= 33199 (0.0762/0.0760)

= 33286 cfm

Q2 = Q5

= Q3 (ρ3/ρ5)

= 33199 (0.0762/0.0763)

= 33155 cfm

FAN POWER INPUT

Measured amps/FLA = (47.7/49.7)

= 0.96

= 96%

Annex K indicates that Equation A will provide a

reasonably accurate estimate of motor power output

for a 40 hp motor operating at 96% FLA.

Hmo = 40 (47.7/49.7) (442/440)

= 38.6 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 4.5%.

HL = 0.045 Hmo

= 0.045 × 38.6

= 1.74 hp

H = Hmo - HL

= 38.6 - 1.74

= 36.86 hp

SYSTEM EFFECT FACTOR

To determine SEF 1, AMCA Publication 201-90,

Figures 7.1 and 8.5, indicate the following

calculations:

V2 = (Q2/A2)

= (33155/15.42)

= 2150 fpm

Duct diameter equivalent to the fan outlet area:

De2 = (4 A2/π)0.5

= (4 × 15.42/π)0.5

= 4.43 ft

For velocities of 2500 fpm or less, the 100% effective

outlet duct length is 2.5 duct diameters:

= 2.5 × 4.43

= 11.1 ft

The length of the outlet duct in % effective duct

length:

= (L/11.1) 100

= (2.0/11.1) 100

= 18%

Blast area ratio = Blast Area/A2

= 9.4/15.42

= 0.61

For a blast area ratio of 0.6, 18% effective duct length

and elbow position A, Figure 8.5 shows SystemEffect Curve R applies. For 2150 fpm velocity and

curve R, Figure 7.1 shows SEF 1 = 0.34 in. wg at

0.075 lbm/ft3 density. At 0.0762 lbm/ft3:

SEF 1 = 0.34 (0.0762/0.075)

= 0.35 in. wg

FAN SECTION STATIC PRESSURE

Pv1 = (Q1/1096 A1)2 ρ1

= (33286/1096 × 147.2)2 0.0760

= 0.003 in. wg

It is assumed that Ps2 = Ps5

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= 1.39 - (-0.847) - 0.003 + 0.35

= 2.58 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 33286 (1430/1402)

= 33951 cfm

Psc = 2.58 (1430/1402)2 (0.075/0.0760)

= 2.65 in. wg

Hc = 36.86 (1430/1402)3 (0.075/0.0760)

= 38.60 hp

AMCA 203-90 (R2007)

79

AMCA 203-90 (R2007)

1. The subject of the test in this example is the air

conditioning unit assembly. This assembly does not

include the inlet plenum. The performance ratings for

the unit assembly are based on operation with the

outlets of the fans ducted. Before proceeding with the

test, it is essential that all system dampers be fixed in

the positions agreed upon by all interested parties as

being applicable for the installation. Also, the

temperature of the cooling coil must be kept constant

throughout the test period. It may be necessary to

lock out, disconnect or otherwise modify automatic

control devices in order to prevent the positions of the

dampers and the temperature of the coil from

changing during the test. Refer to Section 17.4.1 for

additional considerations affecting the test procedure

in this type of installation.

2. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located near the end of a straight

run of duct, as shown in the diagram. Determine Ps3

by averaging the static pressure measurements

made in the same traverse. This static pressure value

is used to determine the density at the traverse

plane. Procedures for traverses are described in

Section 9.4. in order to determine the air flow rate, it

is necessary to measure the area of the traverse

plane.

3. Ps4 may be determined by averaging the pressure

measurements at each of four static pressure taps or

by averaging the static pressure measurements

made in a Pitot-static tube traverse of Plane 4. Ps5 is

determined in a similar manner. However, if it is

possible to install suitable static pressure taps, their

use is preferred in the regions of the outlets of the

fans. Due to the close proximity of Planes 1 and 4

and the fact that there is no change in area between

the two planes, the conditions which exist at Plane 4

are assumed to exist at Plane 1. Although Plane 5 is

greater in area that Plane 2, the degree of divergence

is relatively small. Therefore, Ps2 will be calculated

based on Ps5 and the assumption that there is no

change in total pressure from Plane 2 to Plane 5.

4. Measure the dry-bulb and wet-bulb temperatures

at Plane 4 and the dry-bulb temperatures at Planes 3

and 5. In this example, the cooling medium, normally

circulated in the coil was shut off in order to maintain

constant air temperatures during the test. In order to

account for water vapor which may have been added

to the air as a result of evaporation of moisture

previously condensed on the coil, the wet-bulb

temperature at Plane 3 was measured. Determine pb

for the general vicinity of the air conditioning unit.

These measurements are used in determining

densities at the planes of interest.

COMMENTS

23

5

SEF 1

FANSFILTERS

COOLING COIL

INLET PLENUM

L

PLAN VIEW14

SIDE VIEW

+

+

EXAMPLE 4C: PACKAGED AIR-CONDITIONING UNIT

80

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data including volts (NPV), and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

6. Although an elbow is located shortly downstream

of the fans, SEF 1 is judged to be more closely

characterized as the effect due to insufficient lengths

of duct on the outlets of the fans. In order to

determine the value of SEF 1, it is necessary to

measure the outlet area and the blast area of one of

the fans and the length, L, of its outlet duct.

7. To calculate the static pressure for the unit

assembly:

Ps = Ps2 - Ps1 - Pv1 + SEF 1

Where:

Ps1 = Ps4

Pv1 = (Q1/1096A1)2 ρ1

Ps2 = Ps5 + Pv5 - Pv2

Pv2 and Pv5 are calculated in manners similar to the

calculation of Pv1.

8. In order to compare the test results to the quoted

unit assembly curve drawn for operation at 1050 rpm

and 0.075 lbm/ft3 density, it is necessary to convert

the results to the specified conditions. The basis for

the calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.65 in. Hg

td3 = 75.0°F

tw3 = 59.5°F

td4 = 72.5°F

tw4 = 58.5°F

td5 = 74.5°F

Ps3 = 2.02 in. wg

Pv3 = 0.35 in. wg

Ps4 = -0.32 in. wg

Ps5 = 2.11 in. wg

N = 1025 rpm

A1 = A4

= 31.7 ft2

A2 = 11.5 ft2

A3 = 16.4 ft2

A5 = 14.3 ft2

Blast Area = 4.0 ft2 per fan

L = 2.0 ft, length of outlet duct

MEASURED MOTOR DATA

Volts = 460, 455, 465

= 460 av

Amps = 38.2, 38, 37.9

= 38.0 av

MOTOR NAMEPLATE DATA

25 hp, 3 phase, 60 hertz

460 volts, 1760 rpm, 39.5 FLA

GENERAL

Fans connected to motor through belt drive.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 75.0°F

tw3 = 59.5°F

p3 = pb + (Ps3/13.6)

= 29.65 + (2.03/13.6)

= 29.80 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0736

lbm/ft3.

For Plane 4 conditions of:

td4 = 72.5°F

tw4 = 58.5°F

p4 = pb + (Ps4/13.5)

= 29.65 + (-0.32/13.6)

= 29.63 in. Hg

Use Figure N.1 in Annex N to obtain ρ4 = 0.0735

lbm/ft3.

It is assumed that ρ1 = ρ4.

AMCA 203-90 (R2007)

81

It is assumed ρ2 = ρ5.

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.35/0.0736)0.5

= 2390 fpm

Q3 = V3A3

= 2390 × 16.4

= 39196 cfm

Q2 = Q5

= Q3 (ρ3/ρ5)

= 39196 (0.0736/0.0737)

= 39143 cfm

Q = Q1 = Q4

= Q3 (ρ3/ρ4)

= 39196 (0.0736/0.0735)

= 39249 cfm

FAN POWER INPUT

Measured amps/FLA = (38.0/39.5)

= 0.96

= 96%

Annex K indicates that Equation A will provide a

reasonably accurate estimate of motor power output

for a 25 hp motor operating at 96% FLA.

Hmo = 25 (38.0/39.5) (460/460)

= 24.1 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 4.8%.

HL = 0.048 Hmo

= 0.048 × 24.1

= 1.2 hp

H = Hmo - HL

= 24.1 - 1.2

= 22.9 hp

SYSTEM EFFECT FACTOR

To determine SEF 1, AMCA Publication 201-90,

Figures 7.1 and 8.3, indicate the following

calculations:

V2 = (Q2/A2)

= (39143/11.5)

= 3404 fpm

Duct diameter equivalent to the outlet area of one fan:

De2 = (4A2/2π)0.5

= (4 × 11.5/2π)0.5

= 2.71 ft

Figure 8.3 shows that for velocities over 2500 fpm,

100% effective duct length is one diameter for every

1000 fpm:

= De2 (V2/1000)

= 2.71 (3404/1000)

= 9.22 ft

L in % effective duct length:

= (L/9.22) 100

= (2.0/9.22) 100

= 22%

Blast area ratio = Blast area/A2

= (2 × 4.0)/11.5

= 0.70

For a blast area ratio of 0.7, and 22% effective duct

length Figure 8.3 shows System Effect Curve W

applies. For 3404 fpm velocity and curve W, Figure

7.1 shows SEF 1 = 0.13 in. wg at 0.075 lbm/ft3

density. At 0.0737 lbm/ft3:

SEF 1 = 0.13 (0.0737/0.075)

= 0.13 in. wg

STATIC PRESSURE OF UNIT

Pv5 = (Q5/1096 A5)2 ρ5

= (39143/1096 × 14.3)2 0.0737

= 0.46 in. wg

Pv2 = (Q2/1096 A2)2 ρ2

= (39143/1096 × 11.5)2 0.0737

= 0.71 in. wg

ρ ρ5 3

3

13 6

13 6

460

460

0 07362 11

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

P pp

tt

s5 b d3

d5

.

.

.. ++ ×

×⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

13 6 29 65

13 6 29 80

535

534 5

0 0737

. .

. . .

. lbm/ft3

AMCA 203-90 (R2007)

82

Ps2 + Pv2 = Ps5 + Pv5

Ps2 = Ps5 + Pv5 - Pv2

= 2.11 + 0.46 - 0.71

= 1.86 in. wg

Pv1 = (Q1/1096 A1)2 ρ1

= (39249/1096 × 31.7)2 0.0735

= 0.09 in. wg

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= 1.86 - (-0.32) - 0.09 + 0.13

= 2.22 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 39249 (1050/1025)

= 40206 cfm

Psc = 2.22 (1050/1025)2 (0.075/0.0735)

= 2.38 in. wg

Hc = 22.9 (1050/1025)3 (0.075/0.0735)

= 25.1 hp

AMCA 203-90 (R2007)

83

AMCA 203-90 (R2007)

1. The subject of the test in this example is the air

conditioning unit assembly. This assembly includes

the filter section and the inlet louver. The

performance ratings for the unit assembly are based

on operation with the outlets of the fans ducted.

Before proceeding with the test, it is essential that all

system dampers be fixed in the positions agreed

upon by all interested parties as being applicable for

the installation. Also, the temperature of the heating

coil must be kept constant throughout the test period.

It may be necessary to lock out, disconnect or

otherwise modify automatic control devices in order

to prevent the positions of the dampers and the

temperature of the coil from changing during the test.

Refer to Section 17.5.1 for additional considerations

affecting the test procedure in this type of installation.

2. Normally, velocity pressure measurements would

be made in a single plane, located in a duct common

to all branches. In this example, a measurement

plane which provides a satisfactory velocity profile

cannot be located upstream of the fans or between

the point of connection of the branch ducts and the

outlets of the fans. The alternative, as indicated in the

diagram, is to make a velocity pressure

measurement traverse in each of two branches. the

velocity pressure for reach branch is determined by

using the root mean square of the velocity pressure

measurements made in the traverse. The static

pressure at each traverse plane is determined by

using the root mean square of the velocity

measurement traverse in each of two branches. The

velocity pressure for each branch is determined by

using the root mean square of the velocity pressure

measurements made in the traverse. The static

pressure at each traverse plane is determined by

averaging the static pressure measurements made in

the same traverse. These static pressure values are

used in determining the densities at the traverse

planes. Procedures for traverses are described in

Section 9.4. In order to determine the air flow rates, it

is necessary to measure the area of each traverse

plane.

3. Determine Ps5 by averaging the pressure

measurements at each of four static pressure taps

located in the duct fitting at the outlets of the fans.

The conditions which exist at Plane 5, including the

static pressure, are assumed to exist at Plane 2,

based on their close proximity and the fact that there

is no change in area between the two planes. In

situations such as this example, it is important to be

certain that all pressure measurements are referred

to the same atmospheric pressure.

4. Measure the dry-bulb and wet-bulb temperatures

at Plane 1 and the dry-bulb temperatures at Planes

3a, 3b, and 5. Determine pb for the general vicinity of

COMMENTS

INLET LOUVER

FILTER SECTION

STATIC PRESSURE TAPS

HEATING COIL

SIDE VIEW

PLAN VIEW

SEF 1

3a

3b

25

1

+ +

L

EXAMPLE 4D: PACKAGED AIR-CONDITIONING UNIT

84

the air conditioning unit. These measurements are

used to determine densities at the planes of interest.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV), and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Motor performance data, supplied by the

motor manufacturer, are used in the determination of

motor power output in this example.

6. SEF 1 is due to the effect of insufficient length of

duct between the outlets of the fans and the elbow

downstream of the fans. In order to determine the

value of SEF 1, it is necessary to measure the outlet

area and the blast area of one of the fans and the

length of the duct, L, between the fan and the elbow.

7. The sum of the static pressure, Ps1, and velocity

pressure, Pv1, at the inlet to the unit assembly is

considered to be equal to the sum of the static

pressure, Psx, and velocity pressure, Pvx, at a point

sufficiently distant from the inlet as to be in still air. At

this point, the static pressure is zero, and the velocity

pressure in still air is zero.

Ps1 + Pv1 = Psx + Pvx = 0

This consideration, which is the same as that used in

the methods for testing this type of unit for

performance rating purposes, charges to the unit

losses incurred in accelerating the air into its inlet and

eliminates the inaccuracies which arise in any

attempt to measure the velocity pressure and static

pressure at the inlet. To calculate the static pressure

for the unit assembly:

Ps = Ps2 - Ps1 - Pv1 + SEF 1

= Ps2 - (Ps1 + Pv1) + SEF 1

Since:

Ps1 + Pv1 = 0

Ps = Ps2 + SEF 1

Where:

Ps2 = Ps5

8. In order to compare the test results to the quoted

performance curve for the packaged unit drawn for

operation at 1720 rpm and 0.075 lbm/ft3 density, it is

necessary to convert the results to the specified

conditions. The basis for the calculations is described

in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.65 in. Hg

td1 = 72°F

tw1 = 61°F

td5 = 85°F

td3a = 82.5°F

td3b = 83°F

Ps5 = 1.25 in. wg

Ps3a = 1.15 in. wg

Ps3b = 1.22 in. wg

Pv3a = 0.56 in. wg

Pv3b = 0.60 in. wg

N = 1710 rpm

A2 = A5

= 5.64 ft2

A3a = 3.1 ft2

A3b = 2.2 ft2

Blast Area = 2.5 ft2 per fan

L = 0.96 ft, length of outlet duct

MEASURED MOTOR DATA

Volts = 460, 458, 462

= 460 av

Amps = 10.0, 10.0, 9.8

= 9.9 av

MOTOR NAMEPLATE DATA

10 hp, 3 phase, 60 hertz

460 volts, 1750 rpm, 13.5 FLA

GENERAL

Fans connected to motor through belt drive. The

following motor performance data was supplied by

the motor manufacturer:

Motor Efficiency:

82.5% at 1/2 load

84.5% at 3/4 load

84.5% at full load

Power Factor = 0.85

AMCA 203-90 (R2007)

85

DENSITIES

For Plane 1 conditions of:

td1 = 72°F

tw1 = 61°F

p1 = pb

= 29.65 in. Hg

Use Figure N.1 in Annex N to obtain ρ1 = 0.0735

lbm/ft3.

It is assumed that ρ2 = ρ5

FLOW RATES

V3a = 1096 (Pv3a/ρ3a)0.5

= 1096 (0.56/0.0723)0.5

= 3050 fpm

V3b = 1096 (Pv3b/ρ3b)0.5

= 1096 (0.60/0.0722)0.5

= 3159 fpm

Q3a = V3aA3a

= 3050 × 3.1

= 9455 cfm

Q3b = V3bA3b

= 3159 × 2.2

= 6950 cfm

Q = Q1

= Q3a (ρ3a/ρ1) + Q3b (ρ3b/ρ1)

= 9455 (0.0723/0.0735) + 6950 (0.0722/0.0735)

= 16128 cfm

Q2 = Q5

= Q1 (ρ1/ρ5)

= 16128 (0.0735/0.0720)

= 16464 cfm

FAN POWER INPUT

Measured amps/FLA = (9.9/13.5)

= 0.73

= 73%

The data supplied by the motor manufacturer indicate

power factor of 0.85 and motor efficiency of 84.5% for

the motor operating at 73% FLA. Using the

appropriate equation in Section 10.2.2:

Hmo = (3)0.5 × 9.9 × 460 × 0.85 × 0.845/746

= 7.59 hp

Figure L.1 in Annex L indicates estimated belt drive

loss of 5.6%.

HL = 0.056 Hmo

= 0.056 × 7.59

= 0.43 hp

H = Hmo - HL

= 7.59 - 0.43

= 7.16 hp

SYSTEM EFFECT FACTOR

SEF 1 is due to the effect of insufficient lengths of

duct between the outlets of the fans and the elbow

downstream of the fans. AMCA Publication 201-90,

Figures 7.1, 8.1, and 8.5 indicate the following

calculations:

V2 = (Q2/A2)

= (16464/5.64)

= 2919 fpm

Duct diameter equivalent to the outlet area of one

fan:

De2 = (4A2/2π)0.5

= (4 × 5.64/2π)0.5

= 1.89 ft

Figure 8.1 shows that for velocities over 2500 fpm

100% effective duct length is one diameter for every

1000 fpm:

ρ ρ3bs3b b d1

d3b

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

1

1

13 6

13 6

460

460

0 07351

P pp

tt

.

.

... . .

. .

.

22 13 6 29 65

13 6 29 65

532

543

0 0722

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft3

ρ ρ3as3a b d1

d3a

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

1

1

13 6

13 6

460

460

0 07351

P pp

tt

.

.

... . .

. . .

.

15 13 6 29 65

13 6 29 65

532

542 5

0 0723

+ ××

⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

= lbm/ft33

ρ ρ5 1

1

13 6

13 6

460

460

0 07351 25

= +⎛

⎝⎜

⎠⎟

++

⎝⎜

⎠⎟

=

P pp

tt

s5 b d1

d5

.

.

.. ++ ×

×⎛⎝⎜

⎞⎠⎟⎛⎝⎜

⎞⎠⎟

=

13 6 29 65

13 6 29 65

532

545

0 0720

. .

. .

. lbm/ft3

AMCA 203-90 (R2007)

86

= De2 (V2/1000)

= 1.89 (2919/1000)

= 17%

L, in % effective duct length:

= (L/5.52) 100

= (0.96/5.52) 100

= 17%

Blast area ratio = Blast Area/A2

= (2 × 2.5)/5.64

= 0.89

For a blast area ratio of 0.89, 17% effective duct

length and elbow position C, Figure 8.5 shows

System Effect Curve S applies. For 2919 fpm velocity

and curve S, Figure 7.1 shows SEF 1 = 0.43 in. wg at

0.075 lbm/ft3 density. At 0.0720 lbm/ft3:

SEF 1 = 0.43 (0.0720/0.075)

= 0.41 in. wg

STATIC PRESSURE OF UNIT

Ps2 = Ps5

= 1.25 in. wg

Ps = Ps2 + SEF 1

= 1.25 + 0.41

= 1.66 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 16128 (1720/1710)

= 16222 cfm

Psc = 1.66 (1720/1710)2 (0.075/0.0735)

= 1.71 in. wg

Hc = 7.16 (1720/1710)3 (0.075/0.0735)

= 7.44 hp

AMCA 203-90 (R2007)

87

AMCA 203-90 (R2007)

1. This is a factory assembled, blow-through central

station unit. The subject of the test is the fan section,

which is rated by the manufacturer as an assembly of

the fan and the cabinet in which the fan has been

installed. As a blow-through unit, the performance

ratings for the fan section are based on operation

without the fan outlet ducted. Before proceeding with

the test, it is essential that all dampers (outside air,

return air, mixing box, multizone, face and bypass, or

volume control) be fixed in the positions agreed upon

by all interested parties as being applicable for the

installation. Also, the temperatures of heating and

cooling coils must be kept constant throughout the

test period. It may be necessary to lock out,

disconnect, or otherwise modify automatic control

devices in order to prevent the positions of the

dampers and temperatures of the coils from changing

during the test. In instances in which a cooling coil is

located between a velocity pressure traverse plane

and the fan, as in this example, the flow of the cooling

medium should be stopped or its temperature raised

to a level sufficient to prevent condensation on the

cooling coil, otherwise the moisture condensed will

not be properly taken into account in the

determination of fan air flow rate. Refer to Section

17.5.2 for additional considerations affecting the test

procedure in this type of installation.

2. Normally, velocity pressure measurements would

be made in a single plane, located in a duct common

to all branches. In this example, a measurement

plane which provides a satisfactory velocity profile

cannot be located upstream of the fan or between the

point of connection of the branch ducts and the fan

outlet. The alternative, as indicated in the diagram, is

to make a velocity pressure measurement traverse in

each branch. The velocity pressure for each branch

is determined by using the root mean square of the

velocity pressure measurements made in the

traverse. The static pressure at each traverse plane

is determined by averaging the static pressure

measurements made in the same traverse. These

static pressure values are used in determining the

densities at the traverse plane. Procedures for

traverses are described in Section 9.4. In order to

determine the air flow rates it is necessary to

measure the area of each traverse plane.

3. Determine Ps1 by averaging the static pressure

measurements made in a traverse of Plane 1. Ps5

may be determined in a similar manner or by

averaging the pressure measurements at each of

four static pressure taps. If it is possible to install

suitable pressure taps, their use is preferred in the

regions of the fan outlet. Due to the abrupt expansion

in area from Plane 2 to Plane 5, it is assumed that

there is no conversion of velocity pressure at Plane 2

to static pressure at Plane 5. Therefore, it is assumed

COMMENTS

1 25

3a3b

STATIC PRESSURE TAPS

HEATING COILSPRAYSECTION

FILTER SECTION FAN SECTION COOLING COIL

RETURNAIR

OUTSIDEAIR

++

+

+

+

+

+

+

SIDE VIEW

PLAN VIEW

EXAMPLE 4E: CENTRAL STATION AIR CONDITIONING UNIT, FACTORY ASSEMBLED BLOW-

THROUGH TYPE

88

that Ps2 = Ps5. Measure the area of Plane 1 for use in

calculating Pv1.

4. Measure the dry-bulb and wet-bulb temperatures

at Planes 1, 3a, and 3b. Determine pb for the general

vicinity of the air conditioning unit. These

measurements are used to determine densities at the

planes of interest. The measurements of additional

wet-bulb temperatures were made in this example in

order to provide data which may be used to

determine whether the moisture content of the air

changed between Plane 1 and Planes 3a and 3b.

5. Measure the fan speed and the motor amps, volts,

and if possible, watts. Record all pertinent motor

nameplate data, including volts (NPV), and full load

amps (FLA). If the motor power output is to be

estimated by using the phase current method

described in Annex K, it is not necessary to measure

motor watts; however, it may be necessary to

disconnect the drive and measure the no load amps

(NLA) if the motor is not operating at or near its full

load point. Refer to Annex K.

6. Since the performance ratings for the fan section

are based on operation without the fan outlet ducted,

an SEF does not apply for the unducted position.

7. To calculate the Fan Section Static Pressure:

Ps = Ps2 - Ps1 - Pv1

Where:

Ps2 = Ps5

Pv1 = (Q1/1096 A1)2 ρ1

Q1 = Q3a (ρ3a/ρ1) + Q3b (ρ3b/ρ1)

The calculation of Pv1 is often ignored in instances

similar to this example on the basis that the

calculated value of Pv1 is relatively small, and its

omission does not affect the test results significantly.

8. In order to compare the test results to the quoted

fan section curve drawn for operation at 1650 rpm

and 0.075 lbm/ft3 density, it is necessary to convert

the results to the specified conditions. The basis for

the calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 28.85 in. Hg

td1 = 65°F

tw1 = 60°F

td3a = 100°F

tw3a = 71.5°F

td3b = 60°F

tw3b = 58°F

Ps1 = -2.43 in. wg

Ps5 = 6.55 in. wg

Ps3a = 5.35 in. wg

Ps3b = 5.1 in. wg

Pv3a = 0.53 in. wg

Pv3b = 0.60 in. wg

N = 1695 rpm

A1 = 68.9 ft2

A3a = 5.37 ft2

A3b = 6.78 ft2

MEASURED MOTOR DATA

Volts = 570, 575, 565

= 570 av

Amps = 81.5, 82.5, 81

= 81.7

NLA = 19

MOTOR NAMEPLATE DATA

100 hp, 3 phase, 60 hertz

575 volts, 1790 rpm, 95 FLA

GENERAL

Fan connected to motor through belt drive.

CALCULATIONS

DENSITIES

For Plane 1 conditions of:

td1 = 65°F

tw1 = 60°F

p1 = pb + (Ps1/13.6)

= 28.85 + (-2.43/13.6)

= 28.67 in. Hg

Use Figure N.1 in Annex N to obtain ρ1 = 0.0720

lbm/ft3.

For Plane 3a conditions of:

td3a = 100°F

tw3a = 71.5°F

p3a = pb + (Ps3a/13.6)

= 28.85 + (5.35/13.6)

= 29.24 in. Hg

AMCA 203-90 (R2007)

89

Use Figure N.1 in Annex N to obtain ρ1 = 0.0720

lbm/ft3.

For Plane 3b conditions of:

td3b = 60°F

tw3b = 58°F

p3b = pb + (Ps3b/13.6)

= 28.85 + (5.1/13.6)

= 29.23 in. Hg

Use Figure N.1 in Annex N to obtain ρ3b = 0.0741

lbm/ft3.

FLOW RATES

V3a = 1096 (Pv3a/ρ3a)0.5

= 1096 (0.53/0.0691)0.5

= 3035 fpm

V3b = 1096 (Pv3b/ρ3b)0.5

= 1096 (0.60/0.0741)0.5

= 3119 fpm

Q3a = V3aA3a

= 3035 × 5.37

= 16298 fpm

Q3b = V3bA3b

= 3119 × 6.78

= 21147 cfm

Q = Q1

= Q3a (ρ3a/ρ1) + Q3b (ρ3b/ρ1)

= 16298 (0.0691/0.0720) + 21147 (0.0741/0.0720)

= 37405 cfm

FAN POWER INPUT

Measured amps/FLA = (81.7/95)

= 0.86

= 86%

Annex K indicates that the average of the results of

Equation A and Equation B will provide a reasonably

accurate estimate of motor power output for a 100 hp

motor operating at 86% of FLA.

Eqn. A = 100 (81.7/95) (570/575)

= 85.3 hp

Eqn. B = 100 [(81.7 - 19)/(95 - 19)] (570/575)

= 81.8 hp

Hmo = (85.3 + 81.8)/2

= 83.6 hp

Reference to Figure L.1 in Annex L indicates

estimated belt drive loss of 4.2%.

HL = 0.042 Hmo

= 0.042 × 83.6

= 3.5 hp

H = Hmo - HL

= 83.6 - 3.5

= 80.1 hp

FAN SECTION STATIC PRESSURE

Pv1 = (Q1/1096 A1)2 ρ1

= (37405/1096 × 68.9)2 0.0720

= 0.02 in. wg

It is assumed that Ps2 = Ps5

Ps = Ps2 - Ps1 - Pv1

= 6.55 - (-2.43) - 0.02

= 8.96 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 37405 (1650/1695)

= 36412 cfm

Psc = 8.96 (1650/1695)2 (0.075/0.0720)

= 8.84 in. wg

Hc = 80.1 (1650/1695)3 90.075/0.0720)

= 77.0 hp

AMCA 203-90 (R2007)

90

AMCA 203-90 (R2007)

1. The subject of the test in this example is the roof

ventilator assembly. Before proceeding with the test,

refer to Section 17.4 for considerations affecting the

test procedure in this type of installation.

2. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located in the duct which has

been installed on the inlet side of the ventilator.

Determine Ps3 by averaging the static pressure

measurements made in the same traverse.

Procedures for traverses are described in Section

9.4. Measure the area of the traverse plane, A3,

which is located at the tip of the Pitot-static tube. The

duct, temporarily installed for purposes of the test, is

square in cross-section. Its cross-sectional dimensions

were selected as the maximum permissible for its

installation into the opening in the ventilator mounting

curb. The length of the duct is twice its equivalent

diameter and the entrance to the duct is flared in oder

to reduce inlet losses. The installation of a duct of this

size and cross-sectional configuration is judged as

creating no significant effect on the performance of

the ventilator in this example.

3. Ps2, the static pressure at the outlet of the

ventilator, is zero gauge pressure, referred to the

atmospheric pressure in the region of the ventilator

outlet. In situations such as this example, the air may

be discharging from the ventilator into a region in

which the atmospheric pressure is somewhat

different from that to which all other pressure

measurements are referred. When this possibility

exists, it is essential that the static pressure in the

region of the discharging air be measured, referred to

the same atmospheric pressure as used in all other

pressure measurements. In this example, Ps2 was

measured, referred to the same atmospheric pressure

as in the static pressure measurements made at

Plane 3.

4. Measure the dry-bulb and wet-bulb temperatures

at the velocity traverse plane. Determine pb for the

general vicinity of the ventilator. These measurements

are used to determine densities at the planes of interest.

5. Measure the fan speed and the motor amps and

volts. Record all pertinent motor nameplate data. For

the horsepower rating of the motor in this example, it

is recommended that the fan power input be

determined by using the measured watts input to the

motor and motor performance data, obtained from

the motor manufacturer.

6. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1

= Ps2 - (Ps1 + Pv1)

COMMENTS

2

1

3

TEMPORARY DUCTWITH SQUARECROSS-SECTION,De = EQUIVALENTDIAMETER OF DUCT

1.5 De

2 De

EXAMPLE 5A: FREE INLET, FREE OUTLET ROOF VENTILATOR

91

Where:

Ps1 + Pv1 = Ps3 + Pv3

7. In order to compare the test results to the quoted

fan curve drawn for operation at 1180 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.37 in. Hg

td3 = 73.5°F

tw3 = 58.1°F

Ps2 = 0.037 in. wg

Ps3 = -0.085 in. wg

Pv3 = 0.077 in. wg

N = 1177 rpm

A3 = 5.58 ft2

MEASURED MOTOR DATA

Volts = 235, 230, 230

= 232 av

Watts = 755

MOTOR NAMEPLATE DATA

1 hp, 3 phase, 60 hertz

230 volts, 1175 rpm, 3.6 FLA

General

Fan direct connected to motor. Motor efficiency data

supplied by motor manufacturer.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 73.5°F

tw3 = 58.1°F

p3 = pb + (Ps3/13.6)

= 29.37 + (-0.085/13.6)

= 29.36 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0727

lbm/ft3.

It is assumed that ρ1 = ρ3.

FLOW RATE

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.077/0.0727)0.5

= 1128 fpm

Q = Q1 = Q3

= V3A3

= 1128 × 5.58

= 6294 cfm

FAN POWER INPUT

At the measured power input value of 755 watts, the

data supplied by the motor manufacturer indicate

efficiency of 61% for the motor.

Hmo = (755 × 0.61)/746

= 0.62 hp

Since the fan is direct connected to the motor, there

is no drive loss, and:

H = Hmo

= 0.62 hp

FAN STATIC PRESSURE

Ps1 + Pv1 = Ps3 + Pv3

= -0.085 + 0.077

= -0.008 in. wg

Ps = Ps2 - (Ps1 + Pv1)

= 0.037 - (-0.008)

= 0.045 in. wg

CONVERSION TO SPECIFIED CONDITIONS

Qc = 6294 (1180/1177)

= 6310 cfm

Psc = 0.045 (1180/1177)2 (0.075/0.0727)

= 0.047 in. wg

Hc = 0.62 (1180/1177)3 (0.075/0.0727)

= 0.64 hp

AMCA 203-90 (R2007)

92

AMCA 203-90 (R2007)

1. The subject of the test in this example is the

propeller fan assembly. Before proceeding with the

test, refer to Section 17.4 for considerations affecting

the test procedure in this type of installation.

2. Determine Pv3 by using the root mean square of

the velocity pressure measurements made in a

traverse of Plane 3, located in the duct which has

been installed on the inlet side of the fan. Determine

Ps3 by averaging the static pressure measurements

made in the same traverse. Procedures for traverses

are described in Section 9.4. Measure the area of the

traverse plane, A3, which is located at the tip of the

Pitot-static tube. The duct, temporarily installed for

purposes of the test, is square in cross-section, with

side dimension of 1.5 D2. The shape and area of the

duct cross-section were selected on the basis of

minimizing the effect of the duct on the performance

of the fan while providing velocity pressure readings

of measurable magnitudes. The length of the duct is

twice its equivalent diameter, and the entrance to the

duct is flared in order to reduce inlet losses. The

installation of the duct is judged as creating no

significant effect on the performance of the fan in this

example.

3. Ps2, the static pressure at the outlet of the fan, is

zero gauge pressure, referred to the atmospheric

pressure in the region of the fan outlet. In situations

such as this example, the air may be discharging

from the fan into a region in which the atmospheric

pressure is somewhat different from that to which all

other pressure measurements are referred. When

this possibility exists, it is essential that the static

pressure in the region of the discharging air be

measured, referred to the same atmospheric

pressure as used in all other pressure

measurements. In this example, Ps2 was measured,

referred to the same atmospheric pressure as in the

static pressure measurements made at Plane 3.

4. Measure the dry-bulb and wet-bulb temperatures

at the velocity traverse plane. Determine pb for the

general vicinity of the fan. These measurements are

used to determine densities at the planes of interest.

5. Measure the fan speed and the motor amps and

volts. Record all pertinent motor nameplate data. For

the horsepower rating of the motor in this example, it

is recommended that the fan power input be

determined by using the measured watts input to the

motor and motor performance data obtained from the

motor manufacturer.

6. To calculate the Fan Static Pressure:

Ps = Ps2 - Ps1 - Pv1

= Ps2 - (Ps1 + Pv1)

COMMENTS

32

2 De

1.5 De

TEMPORARY DUCTWITH SQUARECROSS-SECTION,De = EQUIVALENTDIAMETER OF DUCT

D2

EXAMPLE 5B: FREE INLET, FREE OUTLET PROPELLER FAN

93

Where:

Ps1 + Pv1 = Ps3 + Pv3

7. In order to compare the test results to the quoted

fan curve drawn for operation at 1725 rpm and 0.075

lbm/ft3 density, it is necessary to convert the results

to the specified conditions. The basis for the

calculations is described in Section 14.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.65 in. Hg

td3 = 85°F

tw3 = 74°F

Ps2 = 0 in. wg

Ps3 = -0.027 in. wg

Pv3 = 0.025 in. wg

N = 1775 rpm

A3 = 5.06 ft2

MEASURED MOTOR DATA

Volts = 230, 225, 230

= 228 av

Watts = 637

MOTOR NAMEPLATE DATA

3/4 hp, 3 phase, 60 hertz

230 volts, 1760 rpm, 4.8 FLA

GENERAL

Fan direct connected to motor. Motor efficiency data

supplied by motor manufacturer.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 85°F

tw3 = 74°F

p3 = pb + (Ps3/13.6)

= 29.65 + (-0.027/13.6)

= 29.65 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0715

lbm/ft3.

It is assumed that ρ1 = ρ3

FLOW RATES

V3 = 1096 (Pv3/ρ3)0.5

= 1096 (0.025/0.0715)0.5

= 648 fpm

Q = Q1 = Q3

= V3A3

= 648 × 5.06

= 3279 cfm

FAN POWER INPUT

At the measured power input value of 637 watts, the

data supplied by the motor manufacturer indicate

efficiency of 65% for the motor.

Hmo = (637 × 0.65)/746

= 0.56 hp

Since the fan is direct connected to the motor, there

is no drive loss, and:

H = Hmo

= 0.56 hp

FAN STATIC PRESSURE

Ps1 + Pv1 = Ps3 + Pv3

= -0.027 + 0.025

= -0.002 in. wg

Ps = Ps2 - (Ps1 + Pv1)

= 0 - (-0.002)

= 0.002 in. wg

This small value is attributed to the loss at the duct

inlet, and the fan is considered to be operating at free

delivery (Ps = 0).

CONVERSION TO SPECIFIED CONDITIONS

Qc = 3279 (1725/1775)

= 3187 cfm

Psc = 0 in. wg

Hc = 0.56 (1725/1775)3 (0.075/0.0715)

= 0.54 hp

AMCA 203-90 (R2007)

94

AMCA 203-90 (R2007)

1. The subject of the test in this example is the roof

ventilator assembly. Before proceeding with the test,

refer to Section 17.1 for considerations affecting the

test procedure in this type of installation.

2. Ps3, the static pressure in the vicinity of the

ventilator inlet, would normally be determined by

averaging the static pressure measurements made in

a Pitot tube traverse. But in this example, a

temporary duct was not installed and the Pitot tube

traverse could not be accomplished. In this method

for testing a nonducted fan, consider the fan static

pressure (Ps) as the differential pressure, as read on

a manometer, between the pressure measured inside

the room (Ps3) and the pressure measured outside

the room in the vicinity of the ventilator outlet (Ps2).

These pressures are measured at a sufficient

distance from the ventilator so as to be unaffected by

the velocity of the entering or leaving air.

3. Ps2 is considered to be zero gauge pressure, but

since this measurement is actually part of the

differential pressure described in paragraph 2, it is

necessary to make only one density correction; the

correction is to the differential pressure, which is the

fan static pressure.

4. Measure the dry-bulb and wet-bulb temperatures

in the region of the inside pressure measurement.

Also, determine pb in the same vicinity.

5. Measure the fan speed and the motor amps and

volts. Record all pertinent motor nameplate data. For

the horsepower rating of the motor in this example, it

is recommended that the fan power input be

determined by using the measured watts input to the

motor and motor performance data obtained from the

motor manufacturer.

6. Airflow rates are determined from the fan

manufacturer’s certified performance ratings. Draw a

fan performance curve from these ratings converted

to operation at the test values of fan speed and

entering air density. The basis for these calculations

is described in Section 14. The fan airflow rate is then

determined by entering this curve at the test values of

fan static pressure and fan power input.

OBSERVATIONS

SITE MEASUREMENTS

pb = 29.19 in. Hg

td3 = 79°F

tw3 = 63°F

Ps2 - Ps3 = 0.13 in. wg

N = 1735 rpm

COMMENTS

2

1

3

EXAMPLE 5C: FREE INLET, FREE OUTLET ROOF VENTILATOR

95

MEASURED MOTOR DATA

Volts = 229, 229, 232

= 230 av

Watts = 1390

MOTOR NAMEPLATE DATA

1.5 hp, 3 phase, 60 hertz

230 volts, 1740 rpm, 4.8 FLA

GENERAL

Fan direct connected to motor. Motor efficiency data

supplied by motor manufacturer.

Fan performance, at standard air density, as supplied

by fan manufacturer for 1750 rpm.

CALCULATIONS

DENSITIES

For Plane 3 conditions of:

td3 = 79°F

tw3 = 63°F

pb3 = pb + (Ps2 - Ps1)/13.6

= 29.19 + (0.13/13.6)

= 29.2 in. Hg

Use Figure N.1 in Annex N to obtain ρ3 = 0.0715

lbm/ft3.

It is assumed that ρ1 = ρ3.

FAN POWER INPUT

At the measured power input value of 1395 watts, the

data supplied by the motor manufacturer indicate

efficiency of 77% for the motor.

Hmo = (1390 × 0.77)/746

= 1.43 hp

Since the fan is direct connected to the motor, there

is no drive loss, and:

H = Hmo

= 1.43 hp

FAN STATIC PRESSURE

The fan static pressure is considered to be the

differential static pressure.

Ps = Ps2 - Ps3

= 0.13 in. wg

It is assumed that Ps1 = Ps3

CONVERSION OF MANUFACTURER’S FAN

RATINGS TO OPERATING CONDITIONS

Rating Point #1

Q1c = 8900 (1735/1750)

= 8824 cfm

Ps1c = 0

H1c = 1.45 (1735/1750)3 (0.0715/0.0750)

= 1.35 hp

Rating Point #2

Q2c = 8520 (1735/1750)

= 8447 cfm

Ps2c = 0.125 (1735/1750)2 (0.0715/0.0750)

= 0.117 in. wg

H2c = 1.50 (1735/1750)3 (0.0715/0.0750)

= 1.39 hp

Rating Point #3

Q3c = 8060 (1735/1750)

= 7991 cfm

Ps3c = 0.25 (1735/1750)2 (0.0715/0.0750)

= 0.234 in. wg

H3c = 1.55 (1735/1750)3 (0.0715/0.0750)

= 1.44 hp

Draw a performance curve for these operating

conditions. Enter the measured values for static

pressure and horsepower on the appropriate curves.

Ideally, these two points will coincide at the same

cfm. However, usually they will not coincide and

should be averaged to determine the fan airflow rate.

If this difference is small, such as in this example, it

is only a reflection of test inaccuracies. If, however,

these differences exceed 10%, the system should be

reanalyzed for SEFs that may have been overlooked,

or for procedural errors in the initial testing.

Point CFM Ps HP

1) 8900 0 1.45

2) 8520 1/8 1.50

3) 8060 1/4 1.55

AMCA 203-90 (R2007)

96

AMCA 203-90 (R2007)

Qa = 8070 cfm (based upon horsepower)

Qb = 8400 cfm (based upon static pressure)

Use:

Q = 8235 cfm (average of above).

.40

.30

.20

.10

07000 8000 9000

BH

P (H

)

1.50

1.25

1.00

CFM(Q)

SP

BHP

x

x

x

xx

x

STA

TIC

PR

ES

SU

RE

IN. W

G (P

s)

Fan Performance at 0.0715 Air Density

97

AMCA 203-90 (R2007)

Total Pressure

Static Pressure

90° ± 0.1°

3D Radius

SECTION A-A

8D

Head shall be free from nicks and burrs.

All dimensions shall be within ±2%.

Note: Surface finish shall be 32 micro in. or better. The static

orifices may not exceed 0.04 in. diameter. The minimum Pitot

tube stem diameter recognized under this standard shall be

0.10 in. In no case shall the stem diameter exceed 1/30 of the

test duct diameter.

8 holes - 0.13D, not to exceed 0.04 in.,

diameter equally spaced and free from burrs.

Hole depth shall not be less than the hole

diameter.

0.5D Radius

0.4DD

0.8D

16D

All other dimensions are the sameas for spherical head pitot-statictubes.

8D

0.2D Diameter

V

XD

X/D V/D X/D V/D

0.000

0.237

0.336

0.474

0.622

0.500

0.496

0.494

0.487

0.477

1.602

1.657

1.698

1.730

1.762

0.314

0.295

0.279

0.266

0.250

0.741

0.936

1.025

1.134

1.228

0.468

0.449

0.436

0.420

0.404

1.796

1.830

1.858

1.875

1.888

0.231

0.211

0.192

0.176

0.163

1.313

1.390

1.442

1.506

1.538

1.570

0.388

0.371

0.357

0.343

0.333

0.323

1.900

1.910

1.918

1.920

1.921

0.147

0.131

0.118

0.109

0.100

ALTERNATE PITOT-STATIC TUBE WITH ELLIPSOIDAL HEAD

Figure B.1

PITOT-STATIC TUBE WITH SPHERICAL HEAD

Annex B. Pitot Static Tubes

98

AMCA 203-90 (R2007)

READING A

FLEXIBLE TUBINGTOTAL PRESSURE = READING ACORRECTED FOR MANOMETERCALIBRATION

READING B

VELOCITY PRESSURE = READING B CORRECTED FORMANOMETER CALIBRATION ANDCALIBRATION FACTOR FOR THEDOUBLE REVERSE TUBE.

TUBE ENDS MUST BE SMOOTHAND FREE FROM BURRS

REVERSE TUBEIMPACT TUBE

STAINLESS STEELTUBING PREFERREDAPPROX. 0.375 in. OD

SECTION VIEW

AIR FLOW

Notes:

1. For use in dirty or wet gas streams.

2. The double reverse tube must be calibrated and used in the same orientation as used in its calibration

3. Also referred to as impact reverse tube, combined reverse tube, and type S tube.

Figure C.1 - Double Reverse Tube

Annex C. Double Reverse Tubes

99

AMCA 203-90 (R2007)

Figure D.1 - Pitot-Static Tube Holder (Typical)

PITOT-STATIC TUBESPLIT BRASS BUSHINGPRESS TO FIT INTO TUBING

DUCT WALL

1½ in. PIPENIPPLE12 in. LONG

1½ in. PIPEHALF-COUPLINGWELDED TO DUCT

STAINLESS STEEL TUBING1 in. OUTSIDE DIA. × 8 ft. LONGSLIP FIT IN BRASS BUSHINGS

CUT-OFF AND REBRAZEAFTER ASSEMBLY

SPLIT BRASSBUSHING

¼ in. OUTSIDE DIA.STAINLESS STEEL TUBINGFOR GAS SAMPLING

BRASSBUSHINGS

0.312 in. DIA.

THERMOCOUPLE

Notes:

1. Apparatus for mounting Pitot-static tube on duct2. For use in large ducts or high velocity gas streams3. 1 in. diameter tube slides inside 1.5 in. pipe, which can be unscrewed and moved to another traverse location4. The gas sampling tube and thermocouple may be omitted if these data are obtained in other manners

Annex D. Pitot-Static Tube Holder

100

AMCA 203-90 (R2007)

DUCT WALL

MAXIMUM 0.125 in. DIAMETERFOR USE IN RELATIVELYCLEAN GASES. MAY BENECESSARY TO INCREASETO 0.312 in. DIAMETERFOR DIRTY OR WET GASES

½ in. PIPE HALF-COUPLINGOR SIMILAR ARRANGEMENT

INSIDE SURFACE OF DUCT ANDEDGE OF HOLE ARE TO BESMOOTH AND FREE FROM BURRS

MINIMUM OF FOUR TAPS,LOCATED 90° APART ANDNEAR THE CENTER OFEACH WALL

STATIC PRESSURE MEASUREMENTREQUIRED AT EACH TAP. USETHE AVERAGE OF THE MEASUREMENTSAS THE STATIC PRESSURE FOR THE PLANE

Figure E.1 - Static Pressure Tap

Figure E.2 - Locations of Static Pressure Taps

Annex E. Static Pressure Tap

101

AMCA 203-90 (R2007)

Ps3Ps4

Pv3

Ps3

Pv3

Ps3

Pv3

Ps5

PLANE 3PLANE 4PLANE 1PLANE 2

PLANE 3 PLANE 5 PLANE 2 PLANE 1

PLANE 5 PLANE 2 PLANE 1 PLANE 4 PLANE 3

Ps4

*SEF 1

FAN STATIC PRESSUREPs = - Ps1 - Pv1 + SEF 1where Ps1 = Ps4 Pv1 = Pv3 Ps2 = 0

FAN STATIC PRESSUREPs = Ps2 - Ps1 - Pv1where Ps2 = Ps5 Ps1 = Ps4 Pv1 = Pv3

Figure F.1 - Fan with Inlet Duct Only *SEF 1 is due tono duct at fan outlet

FAN STATIC PRESSUREPs = Ps2where Ps2 = Ps5 Pt1 = 0

Figure F.2 - Fan with Outlet Duct Only

Ps5

Figure F.3 - Fan with Inlet Duct and Outlet Duct

ALTERNATEPLANE 3

Annex F. Pitot-Static Tube Connections

102

AMCA 203-90 (R2007)

Figure G.1 - Manometer Data

0.5 in. wg20:1 SLOPE RATIO

1 in. wg10:1 SLOPE RATIO

2 in. wg5:1 SLOPE RATIO

10 in. wg1:1

SLOPERATIO

Annex G. Manometer Data

103

AMCA 203-90 (R2007)

VELOCITY PRESSURE READING, in. wg

STANDARD AIR VELOCITY, fpm (×1000)

% U

NC

ER

TAIN

TY IN

VE

LOC

ITY

DE

TER

MIN

ATIO

N

0.3 0.4 0.6 0.8 1 2 3 4 6 8 10 15

0.2

0.3

0.4

0.5

0.6

0.8

1.0

2.0

3.0

4.0

5.0

6.0

8.0

10.0.01 .02 .04 .06 0.1 0.2 0.4 0.6 1 2 3 4 6 8 10

MANO

METER

SLOPE RATIO

20:1

10:1

5:1

2:11:1

Figure G.2 - Uncertainty in Velocity Determination

PERCENT UNCERTAINTY IN VELOCITY DETERMINATION

USING PITOT-STATIC TUBE AND MANOMETER DUE TO MANOMETER SLOPE

Based on an uncertainty equivalent to an indicating column length of 0.05 in. wg in a vertical manometer (1:1 slope

ratio)

104

AMCA 203-90 (R2007)

Figure H.1 - Distribution of Traverse Points for Circular Ducts

INSIDE

DIAMETER

OF DUCT

NUMBER OF

TRAVERSE

POINTS IN

EACH OF 3

DIAMETERS

K1 K2 K3 K4 K5 K6 K7 K8 K9 K10 K11 K12 K13 K14 K15 K16

LESS THAN

8 ft.8 .021 .117 .184 .345 .655 .816 .883 .979

8 ft.

THROUGH

12 ft.

12 .014 .075 .114 .183 .241 .374 .626 .759 .817 .886 .925 .986

GREATER

THAN 12 ft.16 .010 .055 .082 .128 .166 .225 .276 .391 .609 .724 .775 .834 .872 .918 .945 .990

Annex H. Distribution of Traverse Points

In order to obtain a representative average velocity in a duct, it is necessary to locate each traverse point

accurately. It is recommended that the number of traverse points increase with increasing duct size. The

distributions of traverse points for circular ducts, as indicated below, are based on log-linear Pitot traverse method.

D

Xa = D × Ka

Xn

X4

X3

X2X160º

Where:

D is the inside diameter of the duct

Ka is the factor corresponding to the duct size and the traverse point location as indicated in the table below

105

AMCA 203-90 (R2007)

NU

MB

ER

OF

TRAV

ER

SE

PO

INTS

DUCT CROSS-SECTIONAL AREA, ft2

10

15

20

25

30

40

50

60708090

100

10 15 20 25 30 40 50 60 70 80 100 150 200 250 300

Figure H.3 - Recommended Minimum Number

of Traverse Points for Rectangular Ducts

The recommended minimum number of traverse points for rectangular ducts is indicated below in Figure H.3. For

rectangular ducts with cross-sectional areas of 24 square feet and less, the recommended minimum number is 24.

For cross-sectional areas greater than 24 square feet, the minimum number of points increases as indicated in

Figure H.3. The points are to be located in the centers of equal areas with the areas as nearly square as practical

(see Figure H.2). If the flow conditions at the traverse plane are less than satisfactory, the accuracy of the

determination of flow rate may be improved by using more than the recommended minimum number of points.

Fewer points may be used if the flow is very uniform; however, the maximum area covered per point should not

exceed 3 square feet.

X2

Y2

Y

X

Figure H.2 - Distribution of Traverse Points for Rectangular Duct

106

AMCA 203-90 (R2007)

1. Glass-stem thermometersMercury-glass thermometer

Alcohol-glass thermometerPentane-glass thermometersJena or quartz mercury nitrogen thermometers

2. Gas thermometer

3. Resistance thermometersPlatinum-resistance thermometer

Nickel-resistance thermometer

Thermistors4. Thermocouples

Temp of gases and liquids by contact

” ” ””

””

””

Primary standard

Precision; remote readings; temp offluids or solids by contact

Remote readings; temp by contact

Standard for thermocouples

General testing of high temp; remoterapid readings by direct contact

Same as above, especially suited forlow tempFor differential temp in same applica-tions as in glass stem thermometer

For approx temp

Remote-testing

For intensity of narrow spectra bandof high temp radiation (remote)

For intensity of total high temp radi-ation (remote)Approx temp (within temp source)Approx temp (in surface)Standards

Pt-Pt-Rh thermocouple

Chromel-alumel thermocouple

Iron-constantain thermocoupleCopper-constantan thermocoupleChromel-constantan thermocouple

5. Beckman thermometers(metastatic)

6. Bimetallic thermometers

7. Pressure-bulb thermometersGas-filled bulb

Vapor-filled bulbLiquid-filled bulb

8. Optical pyrometers

9. Radiation pyrometers

10. Seger cones (fusion pyrometers)11. Indicating crayons12. Melting and boiling points of materials

1000/3600125/900All except ex-tremely hightemp

-38/575

-100/100-200/70

-38/1000-459/1000

-320/1800

-150/300

Up to 600

500/3000

Up to 2200

Up to 1500Up to 700

9 diff

0/1000

-100/1000

20/500-50/21001500 upward

Any range

Less than0.1 to 10

Less than0.01

Less than0.02 to 5

0.3

0.1

0.1 to 5

0.1 to 15

0.1 to 150.1 to 15

0.018

1, usuallymuch more

2

22

15

50±1%Extremelyprecise

For laboratory useonly

Limitations

In gases, accuracy af-fected by radiation

Requires consid-erable skill to use

High cost; accuracyaffected by radiationin gasesAccuracy affected byradiation in gases

High cost; also, re-quires expensivemeasuring deviceLess accurate thanaboveSubject to oxidation

Must be set for tempto be measuredTime lag; unsuitablefor remote use; un-reliable

Caution must be ex-ercised so that in-stallation is correct

Precision

FF

ApproximateRange

ApplicationNo. Measurement Means

Reprinted by permission from ASHRAE Handbook - 1989 Fundamentals

Table J.1 - Temperature Measurement

Annex J. Instrumentation Characteristics

107

AMCA 203-90 (R2007)

1. Micromanometer

2. Draft gauges

3. Manometer

4. Swinging-vane-type gauge

5. Bourdon-tube type

6. Pressure transducers- strain gauge, capacity, po- tentiometer, crystal, magnet

Very low press. diff.

Moderately low press. diff.

Medium press diff.

Moderately low press. diff.

Medium to high press. diff.,usually to atmosphere

Remote reading, respondsto rapid changes of pressure

0 to 6 in. H20

0 to 10 in. H20

0 to 100 in. H20or Hg

0 to 0.5 in. H200 to 20 in. H20

Any

0.05 to 50,000psi

0.005 to0.001 in. H20

0.005 to0.05 in. H20

0.05 in.

5%

0.05 to 5%

0.1 to 0.5%

Not readily portable; not easy touse with pulsating pressure

Must be leveled carefully

Where used with liquid must becompensated for liquid density

Generally usable to atmosphericpressure only

Subject to damage due to overpress-shock or pulsation

Requires electronic amplifier andreadout device

No. Measurement Means Application Range Precision Limitations

No. Measurement Means Application Range Precision Limitations

1. Smoke puff or airborne solid tracer

2. Deflecting-vane anemometer

3. Revolving-vane anemometer

4. Pitot tube

5. Impact tube and side- wall or other static tap

6. Heated thermocouple anemometer

7. Hot-wire anemometer

Low air velocities in rooms;highly directional

Air velocities in rooms, atoutlets, etc; directional

Moderate air velocities inducts and rooms; some-what directional

Std instrument for mea-surement of duct velocities

High velocities, smalltubes and where air direc-tion may be variable

Air velocities in ducts,velocity distributions

(a) Low air velocities; di-rectional and nondirec-tional available

(b) High air velocities

(c) Transient velocity andturbulence

5 to 50

30 to 24,000

100 to 3000

180 to 10,000with micromanometer600 to 10,000 withdraft gauges; 10,000up with manometer

120 to 10,000with micromanometer;600 to 10,000 withdraft gauges; 10,000 upwith manometer

10 to 2000

1 to 1000

up to 60,000

Awkward to use but valuable intracing air movement

Not well suited for duct readings;needs periodic check calibration

Extremely subject to error withvariations in velocities with spaceor time; easily damaged; needsperiodic calibration

Accuracy falls off at low end ofrange

Accuracy depends upon constancyof static pressure across streamsection

Accuracy of some types not goodat lower end of range; steadystate measurements only

Requires accurate calibration atfrequent intervals; complex,costly

10 to 20%

5%

5 to 20%

1 to 5%

1 to 5%

3 to 20%

1 to 20%

1 to 20%

Reprinted by permission from ASHRAE Handbook - 1989 Fundamentals

Table J.2 - Differential Pressure Measurement

Table J.3 - Velocity Measurement

108

Annex K. Phase Current Method for

Estimating the Power Output of Three

Phase Fan Motors

The power output of three phase motors can be

estimated based on the relationship of motor current

and motor power output. Two equations can be used

in estimating the motor power output. The equations

are as follows:

Equation A:

Where:

Hmo = motor power output

NPH = nameplate horsepower

FLA = full load amps

NPV = nameplate volts

measured volts = average of the measured phase

volts

measured amps = average of the measured phase

amps

Equation B:

Where:

NLA = average of the measured phase values of no

load amps

NPH = nameplate horsepower

FLA = full load amps

NPV = nameplate volts

NLA can usually be obtained with the motor operating

and the motor shaft coupling or belt drive

disconnected. In the case where the fan impeller is

mounted directly on the motor shaft, it will be

necessary to remove the impeller in order to obtain

NLA measurements.

Use Equation A to estimate the Hmo for motors of 5

horsepower and greater, operating at 90% or more of

FLA. The uncertainties will be less than 5%.

Use the average of Equation A and Equation B to

estimate the Hmo for all motors operating at less than

90% of FLA and for 3 horsepower and smaller motors

operating above 90% of FLA. An estimated Hmo less

than 50% of NPH can contain 15% uncertainties or

greater.

Figure K.1 represents the relationship of motor

current and motor power output. The “dashed” lines

between 0% NPH and 100% NPH for motor sizes

shown represents Equation B. The solid lines

between these same end points for the motor sizes

shown represent the general shape of typical motor

calibration amp/load curves. The solid line from

100% NPH and 100% FLA to 0% NPH and 0% FLA

represents Equation A. These curves indicate that if

you average the results of Equation A and Equation

B for a specific measured amp draw, that your results

approach the typical calibration curve. It also points

out that the uncertainties are low if just Equation A is

used above 90% FLA, especially in the larger integral

motor horsepowers.

Many fractional horsepower and small integral

horsepower motors do not have a significant change

in current from no load to full load. The actual amps-

load characteristics for motors of the same

horsepower rating can vary greatly from motor

manufacturer to motor manufacturer. No load

amperage (NLA) varies significantly for the same size

motor between manufacturers. In addition, various

motor design requirements result in different amp-

load characteristics even though the horsepower

ratings of the motors are the same. These are some

of the reasons that Figure K.1 cannot be used to

determine the motor output directly. The chart is only

intended to indicate the accuracy and suitability of

using the above equations for estimating motor

power output.

H NPHmo

Measured amps - NLA

FLA - NLA

Measured volts

NPV= ⎛

⎝⎜⎞⎠⎟⎛⎛⎝⎜

⎞⎠⎟

H NPHmo

Measured amps

FLA

Measured volts

NPV= ⎛

⎝⎜⎞⎠⎟⎛⎝⎜

⎞⎠⎟

AMCA 203-90 (R2007)

109

AMCA 203-90 (R2007)

100

90

80

70

60

50

40

30

20

10

00 10 20 30 40 50 60 70 80 90 100

RATEDHORSEPOWER

% NAMEPLATE HORSEPOWER

MEASURED AMPSFLA

3

5

400

10

2500

12

GENERALIZED CURVES ILLUSTRATING THE RELATIONSHIP OF

HORSEPOWER TO AMPS FOR THREE PHASE MOTORS

Do not use for determining actual motor horsepower

DOTTED LINES PER EQUATION B: Hmo ∝ MEASURED AMPS - NLA/FLA - NLA

CAUTION: THIS CHART IS REPRESENTATIVE ONLY! SINCE THE AMP-LOAD CHARACTERISTICS OF THE

SAME SIZE MOTOR WILL VARY BETWEEN THE VARIOUS MOTOR MANUFACTURERS, IT CANNOT BE USED

TO DETERMINE THE HORSEPOWER OUTPUT OF A MOTOR. USE THE EQUATIONS AS DIRECTED ON THE

PREVIOUS PAGE.

PER EQUATION A: Hmo ∝

110

Annex L. Estimated Belt Drive Loss

Drive loss is defined as follows:

Percent drive loss equals power to driving sheave

minus power from driven sheaves times 100, divided

by power to driving sheave.

There are several things which can affect belt drive

efficiencies. Some of these are:

1) Over-designed drives. This was considered good

practice at one time because the drive would last

longer. It will still last longer but it is more

inefficient.

2) Multiple belts on subminimum diameter sheaves

are less efficient than fewer belts on larger

diameter sheaves. Both the National Electric

Motor Association and the Rubber

Manufacturer’s Association publish data dealing

with minimum recommended sheave diameters.

As these minimum sheave diameters are

approached, the drive loss becomes greater.

3) A larger belt section than required will increase

the drive loss.

4) A badly undertensioned drive will increase the

drive loss.

5) Misaligned drives will increase the drive loss.

Drive loss is manifested as heat in belt drives. Under

ambient conditions of less than 100°F, well designed

drives that operate efficiently will be warm to the

touch immediately after being shut down. If the drive

is uncomfortable to the touch (approximately 140°F

or more), then the drive loss is high. Obviously poorly

tensioned and misaligned drives should be corrected

before estimating brake horsepowers and drive

losses.

AMCA 203-90 (R2007)

111

AMCA 203-90 (R2007)

RANGE OF DRIVE LOSSES FOR STANDARD BELTS

MOTOR POWER OUTPUT, hp

DR

IVE

LO

SS

, % M

OTO

R P

OW

ER

OU

TPU

T*

1

1.5

2

3

4

6

8

10

15

20

30

40

60

80

100

0.3 0.4 0.6 0.8 1 2 3 4 6 8 10 20 30 40 60 80 100 200 300 400 600

HIGHER BELT SPEEDS TEND TO HAVE HIGHER LOSSES

THAN LOWER BELT SPEEDS AT THE SAME HORSEPOWER

*Drive losses are based on the conventional V-belt, which has been the “work horse” of the drive industry for

several decades.

EXAMPLE

• Motor power output, Hmo, is determined to be 13.3 hp

• The belts are the standard type and just warm to the touch immediately after shutdown

• From chart, drive loss = 5.1%

• Drive loss, HL = 0.051 × 13.3

= 0.7 hp

• Fan power input, H = 13.3 - 0.7

= 12.6 hp

Figure L.1 - Estimated Belt Drive Loss

112

Annex M. Density Determinations

M.1 General

This annex contains examples illlustrating the

procedures for determining densities. Determinations

of densities are shown for air and for gases other

than air.

M.2 Determination of the density of air,

general case

Determine air density by using the Psychrometric

Density Chart, shown in Figure N.1 in Annex N, the

Psychrometric Density Table, shown in Annex N, or a

calculation procedure which makes use of perfect

gas relationships and the modified Apjohn equation

for partial vapor pressure. Examples of the use of

these procedures are included in this section. Each

of the procedures requires knowledge of the

pressure, dry-bulb temperature and wet-bulb

temperature of the air.

The Psychrometric Density Chart and the

Psychrometric Density Table are limited to the

temperatures and pressures normally encountered in

fan applications.

Limit the use of the calculation procedure that is

based on perfect gas relationships and illustrated in

Example M2.3, to instances in which the dry-bulb

temperature is 180°F or less. Accurate wet-bulb

temperature measurements are difficult to obtain

when the dry-bulb temperature exceeds 180°F.

When the dry-bulb temperature exceeds 180°F, it

may be necessary to rely on site personnel for the

water vapor content of the air. Alternately,

commercially available instrumentation for dew point

determination may be used. For the procedure

required to determine density based on the data

provided in either of the above cases, refer to

Psychrometric Tables and Charts by Zimmerman and

Lavine.1

EXAMPLE M2.1

The conditions that exist at the inlet of a fan that is

not ducted on the inlet side are:

td1 = 78°F

tw1 = 62°F

Since:

Ps1 = 0

p1 = pb

= 28.60 in. Hg

The wet-bulb depression is:

td1 - tw1 = 78 - 62

= 16°F

For wet-bulb depression of 16°F, dry-bulb

temperature of 78°F and absolute pressure of 28.60

in. Hg, obtain ρ1 = 0.0701 lbm/ft3 by using the

Psychrometric Density Chart in Figure N.1 in Annex N.

EXAMPLE M2.2

The conditions at a fan inlet, located at an elevation

of 1000 ft above sea level are:

Ps1 = -3.45 in. wg

td1 = 85°F

tw1 = 75°F

Barometric pressure, obtained from a nearby airport,

is 29.82 in. Hg at sea level.

Using the data in Figure N.3 in Annex N, the

barometric pressure at 1000 ft above sea level is:

pb = 29.82 × 0.964

= 28.75 in. Hg

The absolute pressure at the fan inlet is:

p1 = pb + (Ps1/13.6)

= 28.75 + (-3.45/13.6)

= 28.50 in. Hg

The wet-bulb depression is:

td1 - tw1 = 85 - 75

= 10°F

For dry-bulb temperature of 85°F, absolute pressure

of 28.50 in. Hg and wet-bulb depression of 10°F, use

the Psychrometric Density Table in Figures N.5 in

Annex N to obtain:

ρ1 = 0.06829 + 10 × 0.000041

= 0.0687 lbm/ft3

Example M2.3

The conditions at a fan inlet are:

Ps1 = -8.75 in. wg

td1 = 146°F

tw1 = 93°F

AMCA 203-90 (R2007)

1. O. T. Zimmerman and I. Lavine, Psychrometric Tables and Charts, 2nd ed. (Dover, N.H.: Industrial Research Service Inc., 1964)

113

The barometric pressure, pb, measured for the

atmosphere to which Ps1 is referred, is 28.15 in. Hg.

The absolute pressure at the fan inlet is:

p1 = pb + (Ps1 /13.6)

= 28.15 + (-8.75/13.6)

= 27.51 in. Hg

Use Figure N.2 in Annex N to obtain saturated vapor

pressure, pe, of 1.562 in. Hg for the wet-bulb

temperature of 93°F.

Use the modified Apjohn equation for partial vapor

pressure, pp, to obtain:

pp = pe - p1 (td1 - tw1)/2700

= 1.562 - 27.51 (146 - 93)/2700

= 1.022 in. Hg

ρ1 is calculated by using perfect gas relationships:

M.3 Determination of the density of air,

special cases

The procedures for the determination of the density

of air that are described in Section M.2 are valid for

dry air, air that is saturated with water vapor and air

that is partially saturated with water vapor. This

section contains alternate procedures for cases in

which it is known that the air is either dry or saturated.

Knowledge that the air is either dry or saturated

eliminates the usual requirement of the wet-bulb

temperature determination; however, it should be

noted that an incorrect assumption of either of these

conditions can result in a significant uncertainty in the

density determination.

EXAMPLE M3.1

Dry air is entering a fan inlet, located at an elevation

of 1000 ft above sea level. The pressure and

temperature at the inlet are:

Ps1 = -15 in. wg

td1 = 95°F

Barometric pressure, obtained from a nearby

airport, is 29.24 in. Hg at sea level.

Using the data in Figure N.3 in Annex N, the

barometric pressure at 1000 ft above seal level is:

pb = 29.24 × 0.964

= 28.19 in. Hg

The absolute pressure at the fan inlet is:

p1 = pb + (Ps1/13.6)

= 28.19 + (-15/13.6)

= 27.09 in. Hg

Dry air at 29.92 in. Hg and 70°F has a density of

0.075 lbm/ft3.

Consider the density of air to be directly

proportional to absolute pressure and inversely

proportional to absolute temperature. The density

of the air at the fan inlet is calculated as follows:

ρ1 = 0.075 (p1/29.92) [(70 + 460)/(td1 + 460)]

= 0.075 (27.09/29.92) [530/(95 + 460)]

= 0.0648 lbm/ft3

EXAMPLE M3.2

Saturated air is enterting a fan inlet, located at an

elevation of 1500 ft above sea level. The pressure

and temperature at the inlet are:

Ps1 = - 6.75 in. wg

td1 = 103°F

Barometric pressure, obtained from a nearby

airport, is 29.66 in. Hg at sea level.

Using the data in Figure N.3 in Annex N, the

barometric pressure at 1500 ft above sea level is:

pb = 29.66 × 0.947

= 28.09 in. Hg

The absolute pressure at the fan inlet is:

p1 = pb + (Ps1/13.6)

= 28.09 + (-6.75/13.6)

= 27.59 in. Hg

Refer to Figure N.4 in Annex N to obtain saturated

air density of 0.06868 at 103°F and 29.92 in. Hg.

Assuming the density of saturated air to be directly

proportional to absolute pressure, the density at the

fan inlet is calculated as follows:

ρ1

11 3257 0 378

460

1 3257 27 51 0 378 1 022

14

=−( )

+( )

=− ×( )

. .

. . . .

p pt

p

d1

66 460

0 0593

+( )

= . lbm/ft3

AMCA 203-90 (R2007)

114

AMCA 203-90 (R2007)

ρ1 = 0.06868 (p1/29.92)

= 0.06868 (27.59/29.92)

= 0.0633 lbm/ft3

Assuming the density of saturated air to be directly

proportional to absolute pressure is an

approximation. The uncertainty in the density

determination as a result of this approximation

increases with increasing temperature and

increases with increasing variation between the

actual absolute pressure and 29.92 in. Hg, which is

the stated pressure for the data in Figure N.4. The

uncertainty will be approximately 1% or less under

the following conditions:

• At 120°F and at an absolute pressure within 20%

of 29.92 in. Hg

• At 150°F and at an absolute pressure within 10%

of 29.92 in. Hg

• At 180°F and at an absolute pressure within 4%

of 29.92 in. Hg

M.4 DETERMINATION OF THE DENSITY OF A

GAS OTHER THAN AIR

The determination of the density of a gas other than

air may require the use of complex equipment.

Unless specifically qualified, an expert should be

consulted for the proper use of the equipment. If the

gas is a complex mixture of various consitutuents, as

found in certain industrial processes, it is suggested

that the company chemist be consulted for the gas

analysis. Particular care should be used if the gas is

toxic, corrosive or explosive; and in these cases,

consideration should be given to substituting air for

the test.

The first two examples in this section illustrate gas

density determinations based on analyses that

provide the relative amounts of the gas constituents.

Typical flue gas density data, which is provided in

Figure N.6 in Annex N, is illustrated in Example M4.3.

Since the actual density may be significantly different

from the density determined by using typical data, it

is recommended that the typical data be used only in

the even that more specific information is not

available.

EXAMPLE M4.1

A gas is entering a fan inlet located at an elevation of

2000 ft above sea level. The pressure and

temperature at the inlet are:

Ps1 = - 22 in. wg

td1 = 230°F

Barometric pressure, obtained from a nearby airport,

is 29.92 in. Hg at sea level. The composition of the

gas is 5.5% CO2, 1% CO, 15% O2, 1% H2, and 77.5%

N2, by volume.

The apparent molecular weight of the gas is

determined as follows:

Apparent molecular weight = (29.22/1.00)

= 29.22

The density of the gas at 70°F and 29.92 in. Hg is

calculated as follows:

Using the data in Figure N.3 in Annex N, the

barometric pressure at 2000 ft above sea level is:

pb = 29.92 × 0.930

= 27.83 in. Hg

The absolute pressure at the fan inlet is:

p1 = pb + (Ps1/13.6)

= 27.83 + (-22/13.6)

= 26.21 in. Hg

Consider the density of the gas to be directly

proportional to absolute pressure and inversely

proportional to absolute temperature. The density of

the gas at the fan inlet is calculated as follows:

ρ1 = 0.0756 (p1/29.92)[(70 + 460)/(td1 + 460)]

= 0.0756 (26.21/29.92) [530/(230 + 460)]

= 0.0509 lbm/ft3

EXAMPLE M4.2

The conditions that exist at the inlet of a fan are Ps1 =

-19.5 in. wg and td1 = 240°F. The barometric pressure,

Apparent molecular weight

lbm/ft3

386 7

29 22

386 7

0 0756

.

.

.

.

=

=

Component

Volume

Fraction ×

Molecular

Weight = lb/mole

CO2

CO

O2

H2

N2

0.055

0.01

0.15

0.01

0.775

1.00

44

28

32

2

28

2.42

0.28

4.80

0.02

21.70

29.22

115

AMCA 203-90 (R2007)

pb, measured for the atmospheric to which Ps1 is

referred is 29.35 in. Hg. The composition of the gas

is 5.5% CO2, 1% CO, 15% O2, 1% H2, and 77.5% N2

by weight.

The apparent molecular weight of the gas is

determined as follows:

Apparent molecular weight = 1/0.0390

= 25.6

The density of the gas at 70°F and 29.92 in. Hg is

calculated as follows:

The absolute pressure at the fan inlet is:

p1 = pb + (Ps1/13.6)

= 29.35 + (-19.5/13.6)

= 27.92 in. Hg

Consider the density of the gas to be directly

proportional to absolute pressure and inversely

proportional to absolute temperature. The density of

the gas at the fan inlet is calculated as follows:

ρ1 = 0.0662 (p1/29.92)[(70 + 460)/(td1 + 460)]

= 0.0662 (27.92/29.92) [530/(240 + 460)]

= 0.0468 lbm/ft3

EXAMPLE M4.3

Flue gas is flowing at Plane 3, the Pitot traverse

measurement plane. The flue gas is the result of

using natural gas as the fuel. The conditions that

exsit at Plane 3 are:

Ps3 = 5.74 in. wg

td3 = 680°F

The barometric pressure, pb, measured for the

atmosphere to which Ps3 is referred is 28.85 in. Hg.

The absolute pressure at Plane 3 is:

p3 = pb + (Ps3/13.6)

= 28.85 + (5.74/13.6)

= 29.27 in. Hg

Refer to Figure N.6 in Annex N to obtain typical flue

gas density when natural gas is used as the fuel of

0.0725 lbm/ft3 at 70°F and 29.92 in. Hg.

Consider the density of the flue gas to be directly

proportional to absolute pressure and inversely

proportional to absolute temperature. The density of

the gas at Plane 3 is calculated as follows:

ρ1 = 0.0725 (p3/29.92)[(70 + 460)/(td3 + 460)]

= 0.0725 (29.27/29.92) [530/(680 + 460)]

= 0.0330 lbm/ft3

Apparent molecular weight

lbm/ft3

386 7

25 6

386 7

0 0662

.

.

.

.

=

=

Component

Volume

Fraction ×

Molecular

Weight = lb/mole

CO2

CO

O2

H2

N2

0.055

0.01

0.15

0.01

0.775

1.00

44

28

32

2

28

0.00125

0.00036

0.0047

0.005

0.0277

0.0390

116

AMCA 203-90 (R2007)

AM

CA

203-9

0 (

R2007)

t w °F

p ein

. H

g

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

.1646

.1724

.1805

.1879

.1956

.2036

.2118

.2204

.2292

.2384

.2478

.2576

.2678

.2783

.2892

.3004

.3121

.3241

.3365

.3494

.3626

.3764

.3905

.4052

.4203

.4359

.4520

.4687

.4859

.5036

t w °F

p ein

. H

g

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

.5219

.5408

.5603

.5804

.6011

.6225

.6445

.6667

.6906

.7148

.7397

.7653

.7917

.8188

.8468

.8757

.9053

.9359

.9673

.9997

1.0

33

1.0

67

1.1

03

1.1

39

1.1

76

1.2

14

1.2

54

1.2

94

1.3

36

1.3

79

t w °F

p ein

. H

g

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

1.4

23

1.4

68

1.5

15

1.5

62

1.6

11

1.6

62

1.7

14

1.7

67

1.8

21

1.8

77

1.9

35

1.9

94

2.0

54

2.1

17

2.1

80

2.2

46

2.3

13

2.3

81

2.4

52

2.5

25

2.5

99

2.6

75

2.7

53

2.8

33

2.9

15

2.9

99

3.0

85

3.1

73

3.2

63

3.3

56

t w °F

p ein

. H

g

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

3.4

51

3.5

48

3.6

47

3.7

49

3.8

53

3.9

60

4.0

69

4.1

80

4.2

95

4.4

12

4.5

31

4.6

54

4.7

79

4.9

08

5.0

38

5.1

73

5.3

10

5.4

50

5.5

93

5.7

40

5.8

89

6.0

43

6.1

99

6.3

59

6.5

22

6.6

89

6.8

60

7.0

34

7.2

12

7.3

94

t w °F

p ein

. H

g

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

7.5

80

7.7

70

7.9

63

8.1

61

8.3

62

8.5

69

8.7

79

8.9

94

9.2

13

9.4

37

9.6

65

9.8

98

10.1

4

10.3

8

10.6

3

10.8

8

11.1

3

11.4

0

11.6

6

11.9

4

12.2

1

12.5

0

12.7

9

13.0

8

13.3

8

13.6

9

14.0

0

14.3

2

14.6

4

14.9

4

15.3

1

Adapte

d f

rom

AS

HR

AE

Handbook -

1989 F

andam

enta

ls

Fig

ure

N.2

- T

herm

od

yn

am

ic P

rop

ert

ies o

f W

ate

r at

Ab

so

lute

Vap

or

Pre

ssu

res,

Inch

es o

f M

erc

ury

AM

CA

203-9

0 (

R2007)

An

nex N

. D

en

sit

y C

hart

s a

nd

Tab

les

117

118

Fold

out

for

Fig

ure

N.1

- P

sychro

metr

ic D

ensity C

hart

s

AM

CA

203-9

0 (

R2007)

DR

Y-B

ULB

TE

MP

ER

ATU

RE

, °F

WET-BULB DEPRESSION, °F

AIR DENSITY, lbm/ft3

0.06

0

0.06

1

0.06

2

0.06

3

0.06

4

0.06

5

0.06

6

0.06

7

0.06

8

0.06

9

0.07

0

0.07

1

0.07

2

0.07

3

0.07

4

0.07

5

0.07

6

0.07

7

0.07

8

0.07

9

0.08

00246810121416182022242628303234363840

4244

4648

5052

5456

5860

6264

6668

7072

7476

7880

8284

8688

9092

9496

98

1.

Cal

cula

te w

et-b

ulb

depr

essi

on. E

nter

cha

rt at

the

left.

2.

Pro

ceed

hor

izon

tally

to th

e ap

prop

riate

dry

-bul

b

t

empe

ratu

re.

3.

Rea

d ve

rtica

lly to

the

abso

lute

pre

ssur

e.

4.

The

n re

ad h

oriz

onta

lly to

the

dens

ity.

Exam

ple

•Given

:t d

= 54

°F; t

w =

50°

F; p

b = 2

9.9

in. H

g

•Solution:

W

et-b

ulb

depr

essi

on =

4°F

; pro

ceed

hor

i-

zo

ntal

ly to

54°

F dr

y-bu

lb te

mpe

ratu

re;

read

ver

tical

ly to

29.

9 in

. Hg;

read

hor

izon

-

ta

lly to

the

dens

ity --

ρ =

0.0

769

lbm

/ft3 .

28.0

28.2

28.4

28.6

28.8

29.0

29.2

29.4

29.6

29.8

30.0

ABSOLUTE PRESSURE in. Hg

Fig

ure

N.1

- P

sych

rom

etr

ic D

en

sit

y C

hart

119

AMCA 203-90 (R2007)

ALTITUDE

ft.

SPECIFIC

GRAVITY

PRESSURE

in. Hg

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

2400

2500

2600

2700

2800

2900

1.00

0.996

0.993

0.989

0.986

0.982

0.979

0.975

0.971

0.968

0.964

0.961

0.957

0.954

0.950

0.947

0.944

0.940

0.937

0.933

0.930

0.926

0.923

0.920

0.916

0.913

0.909

0.906

0.903

0.899

29.92

29.81

29.70

29.60

29.49

29.38

29.28

29.17

29.07

28.96

28.86

28.75

28.65

28.54

28.44

28.33

28.23

28.13

28.02

27.92

27.82

27.72

27.62

27.52

27.42

27.32

27.21

27.11

27.01

26.91

ALTITUDE

ft.

SPECIFIC

GRAVITY

PRESSURE

in. Hg

3000

3200

3400

3600

3800

4000

4200

4400

4600

4800

5000

5200

5400

5600

5800

6000

6500

7000

7500

8000

8500

9000

9500

10000

15000

20000

25000

30000

35000

40000

0.896

0.890

0.833

0.877

0.870

0.864

0.857

0.851

0.845

0.838

0.832

0.826

0.820

0.814

0.807

0.801

0.786

0.772

0.757

0.743

0.729

0.715

0.701

0.688

0.564

0.460

0.371

0.297

0.235

0.185

26.82

26.62

26.42

26.23

26.03

25.84

25.65

25.46

25.27

25.08

24.90

24.71

24.52

24.34

24.16

23.98

23.53

23.09

22.65

22.22

21.80

21.39

20.98

20.58

16.89

13.75

11.10

8.89

7.04

5.54

Note: Specific gravity of standard air at sea level and 29.92 in. Hg = 1.00

Figure N.3 - Relative Specific Gravity of Air at Various Altitudes1

1. Robert Jorgensen, ed., Fan Engineering, 7th ed. (Buffalo, NY, Buffalo Forge Co., 1970) p.8 - Reprinted by Permission

Temp

°F

WEIGHT IN A

CUBIC FOOT

OF MIXTUREVOLUME

ft3/lb

OF

DRY AIR

WEIGHT OF

THE VAPOR

DRY AIR

lb

VAPOR

lb

TOTAL

WEIGHT

lb

lb/lb

OF

DRY AIR

lb/lb

OF

MIXTURE

-25

-20

-15

-10

-5

0

5

10

15

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

.09134

.09025

.08922

.08820

.08723

.08625

.08529

.08434

.08340

.08247

.08230

.08210

.08193

.08173

.08156

.08136

.08117

.08099

.08083

.08063

.08043

.08025

.08006

.07989

.07970

.07952

.07933

.07916

.07897

.07880

.07860

.07843

.07825

.07805

.07788

.000018

.000024

.000031

.000041

.000053

.000068

.000087

.000110

.000140

.000176

.000185

.000193

.000202

.000213

.000222

.000233

.000243

.000254

.000264

.000277

.000290

.000303

.000315

.000327

.000339

.000353

.000364

.000380

.000394

.000409

.000425

.000440

.000456

.000473

.000491

.09136

.09027

.08925

.08824

.08728

.08632

.08538

.08445

.08354

.08264

.08248

.08229

.08213

.08194

.08178

.08159

.08141

.08124

.08109

.08090

.08072

.08055

.08038

.08022

.08004

.07987

.07969

.07954

.07936

.07921

.07902

.07887

.07871

.07852

.07837

10.95

11.07

11.21

11.34

11.46

11.59

11.72

11.85

11.99

12.12

12.15

12.18

12.20

12.23

12.26

12.29

12.32

12.34

12.37

12.40

12.43

12.46

12.49

12.51

12.54

12.57

12.60

12.63

12.66

12.69

12.72

12.75

12.78

12.81

12.84

.00020

.00027

.00035

.00046

.00061

.00080

.00102

.00130

.00168

.00213

.00225

.00235

.00246

.00260

.00272

.00285

.00300

.00314

.00328

.00345

.00362

.00378

.00393

.00409

.00426

.00444

.00460

.00480

.00499

.00519

.00541

.00561

.00583

.00606

.00630

.00020

.00027

.00035

.00046

.00061

.00080

.00102

.00130

.00168

.00213

.00224

.00234

.00245

.00259

.00271

.00284

.00299

.00313

.00327

.00344

.00361

.00376

.00392

.00408

.00425

.00442

.00458

.00478

.00496

.00516

.00538

.00558

.00579

.00602

.00626

Temp

°F

WEIGHT IN A

CUBIC FOOT

OF MIXTUREVOLUME

ft3/lb

OF

DRY AIR

WEIGHT OF

THE VAPOR

DRY AIR

lb

VAPOR

lb

TOTAL

WEIGHT

lb

lb/lb

OF

DRY AIR

lb/lb

OF

MIXTURE

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

.07768

.00750

.07731

.07714

.07694

.07676

.07657

.07637

.07620

.07600

.07582

.07562

.07544

.07524

.07506

.07486

.07468

.07447

.07429

.07408

.07390

.07369

.07350

.07330

.07310

.07290

.07270

.07250

.07229

.07208

.07188

.07166

.07144

.07124

.07104

.000509

.000527

.000545

.000567

.000587

.000608

.000632

.000651

.000675

.000700

.000723

.000749

.000775

.000801

.000829

.000857

.000886

.000916

.000947

.000979

.001012

.001045

.001080

.001115

.001152

.001189

.001229

.001268

.001310

.001352

.001395

.001439

.001485

.001532

.001579

.07819

.07803

.07785

.07771

.07753

.07737

.07720

.07702

.07687

.07670

.07654

.07637

.07622

.07604

.07589

.07572

.07557

.07539

.07524

.07506

.07491

.07473

.07458

.07441

.07425

.07409

.07393

.07377

.07360

.07343

.07328

.07310

.07293

.07277

.07262

12.87

12.90

12.93

12.96

12.99

13.02

13.06

13.09

13.12

13.15

13.19

13.22

13.25

13.29

13.32

13.35

13.39

13.42

13.46

13.49

13.53

13.57

13.60

13.64

13.68

13.71

13.75

13.79

13.83

13.87

13.91

13.95

13.99

14.03

14.08

.00655

.00680

.00705

.00734

.00762

.00792

.00823

.00854

.00884

.00921

.00952

.00989

.01026

.01063

.01103

.01143

.01185

.01229

.01273

.01320

.01368

.01417

.01468

.01520

.01576

.01630

.01691

.01748

.01812

.01876

.01941

.02008

.02079

.02150

.0223

.00651

.00675

.00700

.00728

.00756

.00786

.00819

.00845

.00877

.00913

.00943

.00980

.01016

.01052

.01091

.01130

.01171

.01214

.01257

.01303

.01349

.01397

.01447

.01497

.01551

.01604

.01662

.01717

.01780

.01841

.01904

.01968

.02036

.02106

.02174

Figure N.4 - Weights of Air, Water Vapor, and Saturated Mixture of Air and

Water Vapor at Different Temperatures and 29.92 in. Hg

2. Jorgensen, op. cit., pp 15-17 Reprinted by Permission

PROPERTIES OF SATURATED AIR2

AMCA 203-90 (R2007)

120

Temp

°F

WEIGHT IN A

CUBIC FOOT

OF MIXTUREVOLUME

ft3/lb

OF

DRY AIR

WEIGHT OF

THE VAPOR

DRY AIR

lb

VAPOR

lb

TOTAL

WEIGHT

lb

lb/lb

OF

DRY AIR

lb/lb

OF

MIXTURE

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

.07081

.07059

.07038

.07015

.06993

.06970

.06947

.06925

.06902

.06880

.06855

.06832

.06809

.06785

.06760

.06736

.06711

.06688

.06660

.06634

.06610

.06583

.06557

.06530

.06504

.06477

.06451

.06421

.06394

.06364

.06336

.06306

.06278

.06247

.06216

.001629

.001680

.001733

.001785

.001840

.001898

.001954

.002014

.002072

.002139

.002201

.002267

.002334

.002404

.002474

.002546

.002620

.002692

.002770

.002853

.002937

.003019

.003106

.003193

.003283

.003375

.003470

.003568

.003666

.003766

.003872

.003978

.004085

.004199

.004311

.07244

.07227

.07211

.07193

.07177

.07160

.07142

.07126

.07109

.07094

.07075

.07058

.07042

.07025

.07007

.06991

.06973

.06957

.06931

.06919

.06904

.06885

.06868

.06849

.06832

.06814

.06798

.06778

.06761

.06741

.06723

.06704

.06686

.06667

.06647

14.12

14.16

14.21

14.26

14.30

14.34

14.39

14.44

14.48

14.53

14.58

14.63

14.69

14.73

14.79

14.84

14.90

14.95

15.01

15.07

15.12

15.18

15.25

15.31

15.37

15.44

15.50

15.57

15.64

15.71

15.78

15.85

15.93

16.00

16.08

.02301

.02380

.02462

.02545

.02631

.02723

.02813

.02908

.03002

.03109

.03211

.03318

.03428

.03543

.03660

.03780

.03904

.04025

.04159

.04300

.04443

.04586

.04737

.04890

.05048

.05212

.05379

.05556

.05734

.05917

.06111

.06308

.06507

.06722

.06935

.02249

.02325

.02403

.02482

.02566

.02651

.02736

.02826

.02915

.03015

.03111

.03212

.03314

.03422

.03531

.03642

.03757

.03870

.03993

.04124

.04255

.04385

.04523

.04662

.04806

.04953

.05105

.05264

.05422

.05587

.05760

.05934

.06110

.06299

.06486

Temp

°F

WEIGHT IN A

CUBIC FOOT

OF MIXTUREVOLUME

ft3/lb

OF

DRY AIR

WEIGHT OF

THE VAPOR

DRY AIR

lb

VAPOR

lb

TOTAL

WEIGHT

lb

lb/lb

OF

DRY AIR

lb/lb

OF

MIXTURE

116

117

118

119

120

121

122

123

124

125

130

135

140

145

150

155

160

165

170

175

180

185

190

195

200

205

210

212

.06186

.06154

.06124

.06092

.06060

.06027

.05995

.05960

.05927

.05892

.05713

.05524

.05319

.05100

.04865

.04612

.04340

.04048

.03734

.03398

.03035

.02645

.02228

.01779

.01297

.00782

.00232

.00000

.004427

.004548

.004669

.004794

.004921

.005049

.005183

.005319

.005456

.005598

.006355

.007195

.008128

.009162

.010303

.011547

.012937

.014436

.016118

.017926

.019905

.022062

.024393

.026957

.029730

.032715

.035942

.037298

.06629

.06609

.06591

.06571

.06552

.06532

.06513

.06492

.06473

.06452

.06349

.06244

.06132

.06016

.05895

.05767

.05634

.05492

.05346

.05191

.05036

.04851

.04667

.04475

.04270

.04064

.03836

.03730

16.16

16.24

16.32

16.41

16.50

16.58

16.68

16.77

16.87

16.96

17.49

18.10

18.79

19.60

20.55

21.67

23.03

24.69

26.77

29.43

32.94

37.78

44.85

56.20

77.11

127.9

431.0

____

.07157

.07390

.07625

.07869

.08121

.08376

.08646

.08925

.09204

.09502

.11125

.13026

.15280

.17966

.21178

.25038

.29810

.35660

.43168

.52750

.65580

.83410

1.0948

1.5153

2.2923

4.1838

15.493

Inf.

.06678

.06882

.07084

.07296

.07511

.07729

.07958

.08194

.08428

.08677

.10010

.11523

.13255

.15230

.17478

.20022

.22962

.26285

.30150

.34530

.39525

.45425

.52270

.60240

.69660

.80500

.93700

1.0000

Figure N.4 - Weights of Air, Water Vapor, and Saturated Mixture of Air and

Water Vapor at Different Temperatures and 29.92 in. Hg

2. Jorgensen, op. cit., pp 15-17 Reprinted by Permission

PROPERTIES OF SATURATED AIR2

AMCA 203-90 (R2007)

121

Dry-Bulb

Temp. °F

Density of Saturated Air for Various Barometric Conditions - lbm/ft3 Approximate

average

increase in

density per

°F wet-bulb

depression

Barometric Pressure in. Hg Increase in

density per

0.1 in.

pressure28.5 29.0 29.5 30.0 30.5 31.0

30

31

32

33

34

.07703

.07687

.07671

.07654

.07638

.07839

.07822

.07806

.07789

.07772

.07974

.07957

.07940

.07924

.07907

.08110

.08093

.08075

.08058

.08041

.08245

.08228

.08210

.08193

.08175

.08380

.08363

.08345

.08327

.08310

.00027

.00027

.00027

.00027

.00027

.000017

.000017

.000017

.000018

.000018

35

36

37

38

39

.07621

.07605

.07589

.07573

.07557

.07756

.07739

.07723

.07706

.07690

.07890

.07873

.07856

.07840

.07823

.08024

.07807

.07990

.07973

.07956

.08158

.08141

.08123

.08106

.08089

.08292

.08274

.08257

.08239

.08222

.00027

.00027

.00027

.00027

.00027

.000018

.000018

.000019

.000019

.000019

40

41

42

43

44

.07541

.07525

.07509

.07493

.07477

.07674

.07657

.07641

.07625

.07609

.07806

.07790

.07773

.07757

.07740

.07939

.07922

.09705

.07889

.07872

.08072

.08055

.08038

.08021

.08004

.08205

.08187

.08170

.08153

.08135

.00027

.00026

.00026

.00026

.00026

.000019

.000020

.000020

.000020

.000020

45

46

47

48

49

.07461

.07445

.07429

.07413

.07397

.07592

.07576

.07560

.07544

.07528

.07724

.07707

.07691

.07674

.07658

.07855

.07838

.07822

.07805

.07788

.07986

.07970

.07953

.07936

.07919

.08118

.08101

.08084

.08066

.08049

.00026

.00026

.00026

.00026

.00026

.000020

.000021

.000021

.000021

.000022

50

51

52

53

54

.07381

.07366

.07350

.07334

.07318

.07512

.07496

.07479

.07464

.07447

.07642

.07625

.07609

.07593

.07576

.07772

.07755

.07739

.07722

.07706

.07902

.07885

.07868

.07852

.07835

.08032

.08015

.07998

.07981

.07964

.00026

.00026

.00026

.00026

.00026

.000022

.000022

.000023

.000023

.000023

55

56

57

58

59

.07302

.07287

.07271

.07255

.07240

.07431

.07415

.07399

.07383

.07367

.07560

.07544

.07528

.07512

.07495

.07689

.07673

.07656

.07640

.07623

.07818

.07801

.07784

.07768

.07751

.07947

.07930

.07913

.07896

.07879

.00026

.00026

.00026

.00026

.00026

.000024

.000024

.000025

.000025

.000025

60

61

62

63

64

.07224

.07208

.07193

.07177

.07161

.07352

.07336

.07320

.07304

.07288

.07479

.07463

.07447

.07430

.07414

.07607

.07590

.07574

.07557

.07541

.07734

.07718

.07701

.07684

.07668

.07862

.07845

.07828

.07811

.07794

.00026

.00026

.00026

.00026

.00026

.000026

.000026

.000027

.000027

.000028

Note: Approximate average decrease in density per 0.1°F rise in dry-bulb temperature equals .000017 lbm/ft3.

Figure N.5 - Psychrometric Density Table (I-P)

AMCA 203-90 (R2007)

122

Psychrometric Density Table (I-P)

Dry-Bulb

Temp. °F

Density of Saturated Air for Various Barometric Conditions - lbm/ft3 Approximate

average

increase in

density per

°F wet-bulb

depression

Barometric Pressure in. Hg Increase in

density per

0.1 in.

pressure28.5 29.0 29.5 30.0 30.5 31.0

65

66

67

68

69

.07145

.07130

.07114

.07098

.07083

.07272

.07256

.07240

.07224

.07208

.07398

.07382

.07366

.07350

.07333

.07525

.07508

.07492

.07475

.07459

.07651

.07634

.07618

.07601

.07584

.07770

.07760

.07744

.07727

.07710

.00026

.00026

.00026

.00026

.00026

.000028

.000029

.000029

.000030

.000030

70

71

72

73

74

.07067

.07051

.07035

.07020

.07004

.07192

.07176

.07160

.07144

.07128

.07317

.07301

.07285

.07268

.07252

.07442

.07426

.07410

.07393

.07377

.07568

.07551

.07534

.07517

.07501

.07693

.07676

.07659

.07642

.07625

.00026

.00025

.00025

.00025

.00025

.000031

.000031

.000032

.000033

.000033

75

76

77

78

79

.06988

.06972

.06956

.06940

.06925

.07112

.07096

.07080

.07064

.07048

.07236

.07220

.07203

.07187

.07171

.07360

.07343

.07327

.07310

.07294

.07484

.07467

.07451

.07434

.07417

.07603

.07591

.07574

.07557

.07540

.00025

.00025

.00025

.00025

.00025

.000034

.000034

.000035

.000036

.000036

80

81

82

83

84

.06909

.06893

.06877

.06861

.06845

.07032

.07015

.07000

.06983

.06967

.07155

.07138

.07122

.07105

.07089

.07277

.07261

.07244

.07227

.07211

.07400

.07383

.07366

.07349

.07333

.07523

.07506

.07489

.07472

.07454

.00025

.00025

.00024

.00024

.00024

.000037

.000038

.000039

.000039

.000040

85

86

87

88

89

.06829

.06812

.06796

.06780

.06764

.06950

.06934

.06917

.06901

.06885

.07072

.07056

.07039

.07022

.07005

.07194

.07177

.07160

.07143

.07126

.07316

.07299

.07281

.07264

.07247

.07437

.07420

.07403

.07385

.07368

.00024

.00024

.00024

.00024

.00024

.000041

.000042

.000043

.000043

.000044

90

91

92

93

94

.06748

.06731

.06715

.06698

.06682

.06868

.06852

.06835

.06818

.06801

.06989

.06972

.06955

.06938

.06921

.07109

.07092

.07075

.07058

.07041

.07230

.07213

.07195

.07178

.07161

.07351

.07333

.07316

.07298

.07280

.00024

.00024

.00024

.00024

.00024

.000045

.000046

.000047

.000048

.000049

95

96

97

98

99

.06665

.06648

.06632

.06615

.06598

.06785

.06768

.06751

.06734

.06717

.06904

.06887

.06870

.06853

.06835

.07024

.07006

.06989

.06972

.06954

.07143

.07126

.07108

.01091

.07073

.07263

.07245

.07227

.07209

.07191

.00024

.00024

.00024

.00024

.00024

.000050

.000051

.000052

.000053

.000054

100 .06581 .06700 .06818 .06937 .07055 .07174 .00024 .000055

Note: Approximate average decrease in density per 0.1°F rise in dry-bulb temperature equals .000017 lbm/ft3.

Figure N.5 - Psychrometric Density Table (I-P)

AMCA 203-90 (R2007)

123

FUEL FLUE GAS DENSITY

lbm/ft3

COAL 0.078

OIL 0.075

NATURAL GAS 0.0725

BAGASSE 0.070

BLAST FURNACE GAS 0.076

LIGNITE 0.073

WOOD 0.070

The above densities at 70°F and 29.92 in. Hg are based on average fuel analyses and moisture contents

Figure N.6 - Typical Densities for Various Flue Gases

AMCA 203-90 (R2007)

124

OUTLET AREA

BLAST AREA

CENTRIFUGAL FAN

AXIAL FAN

CUTOFF

DISCHARGE DUCT

25%

50%

75%

100% EFFECTIVE DUCT LENGTH

To calculate 100% effective duct length, assume a minimum of 2½ duct diameters for 2500 fpm or less. Add 1 duct

diameter for each additional 1000 fpm.

Example: 5000 fpm = 5 equivalent duct diameters

If the duct is rectangular, with side dimensions equal to a and b, the equivalent duct diameter is equal to (4ab/π)0.5

Figure P.1 - Controlled Diffusion and Establishment of a Uniform

Velocity Profile in a Straight Length of Outlet Duct

Annex P. Diffusion at Fan Outlets

AMCA 203-90 (R2007)

125

BEARINGSINLET BOX GUIDE VANES

MECHANISM FORCONTROLLINGBLADE ANGLE

INNER CYLINDER

IMPELLERDIFFUSER

BELT TUBE

CASING

BEARING CASING

BLADE

HUB

IMPELLER

GUIDE VANEVaneaxial Fan-Belt Drive

Tubeaxial Fan-Direct Drive(Impeller Downstream)

DIFFUSERBLADE

HUB

IMPELLER

INLET BELL

CASING

MOTOR

Tubular Centrifugal Fan - Direct Drive

INLET

BACKPLATERIM

HUB

IMPELLER

BLADEGUIDE VANE

MOTOR

CASING

Vaneaxial Mechanical Draft Fan

FANCASING

Figure R.1 - Common Terminology for Axial and Tubular Centrifugal Fans

Annex R. Terminology for Fans and Air Handling Units

AMCA 203-90 (R2007)

126

HOUSING

DIVERTER

CENTER PLATE

SIDE SHEET

CUT OFF

BEARINGSUPPORT

INLET COLLAR

INLET

BLADE

BACKPLATE

IMPELLER

RIM

CUT OFF

BLAST AREADISCHARGE

OUTLET AREA

SCROLL

FRAME

Figure R.2 - Common Terminology for Centrifugal Fan

AMCA 203-90 (R2007)

127

Figure R.3 - Common Terminology for Centrifugal Fan Appurtenances

AMCA 203-90 (R2007)

128

Figure R.4 - Common Terminology for Central Station Air-Handling Units

MB

MB

MB

MB

FB

FB ASHCINT

F & BP

EXTF & BPFS CS

BELT GUARD

FSMB

FBHCFS

ZONE DAMPERS

COLD DECK

HOT DECK

AS FS CC HC SS FB ELIM

DRIP TRAY

HOT DECK

COLD DECK

+

+

++

+

+

+ +

+

+++

+

+

+

++

+++

+

+

AS ACCESS SECTIONCS COIL SECTIONCC COOLING COILHC HEATING COIL

EXT F & BPINT F & BP

ELIM

EXTERNAL FACE AND BYPASS DAMPERINTERNAL FACE AND BYPASS DAMPERELIMINATORS

FS FAN SECTIONFB FILTER BOXMB MIXING BOXSS SPRAY SECTION

BYPASS

FBCCHCFS

DIFFUSERPLATE

AIR-CONDITIONING BLOW-THROUGH UNIT

AIR-CONDITIONING DRAW-THROUGH UNIT

HEATING AND VENTILATING BLOW-THROUGH UNIT

HC

ZONE DAMPERS

CC

FLEXIBLE CONNECTION

HEATING AND VENTILATING DRAW-THROUGH UNIT

AMCA 203-90 (R2007)

129

JOB DESCRIPTION:

FAN DESCRIPTION:

MOTOR DESCRIPTION:

DRIVE DESCRIPTION:

REFERENCE DRAWINGS ORSKETCHES OF INSTALLATION:

MEASUREMENTSAMBIENT DATA:

MOTOR DATA:

FAN SPEED

GAS DENSITY DATA:GAS TEMPERATURES AT MEASUREMENT PLANES:

Location, User, Contractor, Engineer, . . . . .

Mfgr., Size, Type, Ident. No., . . . . .

Mfgr., Nameplate Data (Ident. No., hp, volts, FLA, . . . ), Performance DataReference, . . . . .

Type, Mfgr., Ident. No., Size, . . . . .

System Configuration with Dimensions, Measurement PlaneLocations, . . . . .

volts, amps, watts, rpm, . . . . .

READING Ps1 or Ps4 Ps2 or Ps5 Ps3 Pv3 Pv3

21

345

TOTALAVERAGE

n

••

••

CALCULATIONS: (Refer to the various sections of this publication for the appropriate calculation procedures.)

Barometric Pressure, Dry-Bulb Temp., Wet-Bulb Temp, . . . . .

FIELD TEST DATA SHEET

Figure S.1 - Typical Format for Field Test Data Sheet

Annex S. Typical Format for Field Test Data Sheet

AMCA 203-90 (R2007)

130

AMCA 203-90 (R2007)

Annex T. Uncertainty Analysis

T.1 Introduction

In an attempt to determine the range of uncertainties

likely to be encountered in field testing of fans, a

statistical uncertainty analysis was undertaken.

Maximum and minimum uncertainties were assigned

to each quantity to be measured based on the degree

of difficulty in measuring the quantity, the previously

specified accuracies of instruments and the

conditions expected to be encountered in field

testing. These individual maximum and minimum

uncertainties were then combined statistically to

arrive at the probable range of overall uncertainties

for the fan flow rate, fan static pressure, and fan

power input. It would be unlikely, however, that any

particular field installation would have all minimum or

all maximum uncertainties occurring simultaneously.

Therefore, an agreement by the parties as to

acceptable measurement tolerances for a given

installation should be established prior to testing.

In Type A tests, it may be sufficient to accept the

results of any field test without consideration of the

probable uncertainties in the results. For Type B and

Type C tests, it may be necessary to calculate the

uncertainties. To do this, each measured quantity is

assigned an estimated uncertainty by agreement of

the parties involved and the overall uncertainty is

calculated as outlined in this annex.

T.2 General

This analysis is based on the assumption that fan

perfomance can be treated as a statistical quantity

and that the performances derived from repeated

tests would have a normal distribution. The most

probable performance would, therefore, be the mean

results based on repeated observations at each point

of operation. Only one set of observations is

specified in this publication. This analysis deals,

therefore, with the probable uncertainty in the results

obtained from a single set of observations.

The results of a fan field performance test for a single

point of operation are a combination of variables

which are normally presented graphically. Test results

will be considered to be the fan static pressure

versus flow rate and fan power input versus flow rate.

The uncertainty in results will be expressed in terms

of fan flow rate, fan static pressure, and fan power

input.

The accuracies specified in this publication are based

upon two standard deviations. This means that there

should be a 95% probability that the actual

uncertainties will be less than the specified value.

This applies only to random uncertainties. Systematic

uncertainties should be eliminated by the use of

properly calibrated test instruments. This analysis

considers only the uncertainties inherent in testing.

This publication specifies uncertainties in percent.

These are, of course, per unit uncertainties,

multiplied by 100. Absolute uncertainties which bear

the units of the quantity being measured or

calculated, are equal to the per unit uncertainty

multiplied by the measured or calculated quantity.

Since the tolerance on measured values is specified

on the basis of 95% confidence limits, the actual

deviations in results will be less than the calculated

deviations 95% of the time.

For the purposes of a field test, an uncertainty range

will be defined with minimum and maximum values.

This range of possible uncertainty is necessary to

cover the varying degrees of difficulty encountered in

performing tests in field installations. Field test

conditions range from near ideal to near impossible.

T.3 Symbols

In the analysis that follows, certain symbols and

notations are used in addition to those shown in

Annex Q.

Symbol Quantity

ex Per Unit Uncertainty in X

ΔX Absolute Uncertainty in X

R Gas Constant (ft-lb/lbm —°R)

Subscript Description

A area

b Barometric Pressure

d Dry-bulb Temperature

f Velocity Pressure

g Static Pressure

h Power Input

H Fan Power Input

N Fan Speed

P Fan Static Pressure

Q Fan Flow Rate

w Wet-bulb Depression

x Generalized Quantity (A, b, ..., ρ)

ρ Density

T.4 Measurement uncertainties

The various measurement uncertainty ranges used in

this publication are listed below. The considerations

that led to their adoption include difficulties in field

testing generally not encountered in laboratory

testing.

131

AMCA 203-90 (R2007)

T.4.1 Barometric pressure. The estimated

uncertainty in measuring barometric pressure is

between 0.3% minimum and 0.7% maximum.

eb = 0.003 (min) to 0.007 (max)

Barometric pressure is generally obtained by

portable aneroid barometer, on-site barometer

(mercury or aneroid) or by use of data obtained from

a nearby airport. The uncertainty range above is

estimated based on the use of portable or on-site

instrumentation and applicable corrections.

T.4.2 Dry-bulb temperature. The estimated

uncertainty in measuring dry-bulb temperature is

between 0.5% of absolute temperature minimum and

2.0% of absolute temperature maximum.

ed = 0.005 (min) to 0.02 (max)

The estimated uncertainty range is based on a broad

temeprature range and the likelihood of stratification.

T.4.3 Web-bulb depression. The estimated

uncertainty in measuring wet-bulb depression is

between 5°F minimum and 10°F maximum.

ew = 5/(td - tw) (min) to 10/(td - tw) (max)

The estimated uncertainty range is based on a broad

temperature range with the associated difficulties in

determining wet-bulb readings at high or low

temperatures and the likelihood of stratification.

T.4.4 Fan speed. The estimated uncertainty in

measuring fan speed is between 0.5% minimum and

1.0% maximum.

eN = 0.005 (min) to 0.01 (max)

The uncertainty range in fan speed is estimated on

the basis of portable instrumentation accuracy and

an allowance for fluctuation in fan speed.

T.4.5 Power input. The estimated uncertainty in

measuring power input is betwen 3.0% minimum and

7.0% maximum.

eh = 0.03 (min) to 0.07 (max)

The estimated uncertainty range is based on the

various measurement methods and their respective

accuracies, estimated drive losses, and the broad

horsepower range encountered in the field.

T.4.6 Pitot traverse. A properly performed field

traverse is estimated to have an accuracy of 1.5%

minimum to 7.5% maximum.

ec = 0.015 (min) to 0.075 (max)

The uncertainty range in the Pitot traverse is

estimated on the basis of traverse location, broad

range of duct sizes, nonuniform velocity profiles, and

turbulence.

T.4.7 Flow measurement area. The estimated

uncertainty in the flow measurement area is between

1.0% minimum to 2.0% maximum.

eA = 0.010 (min) to 0.020 (max)

The estimated uncertainty is based on a broad range

of duct sizes, accessibility, and the rigidity of ducts

under pressure.

T.4.8 Velocity pressure. An allowance of 2.0%

minimum to 5.0% maximum of the reading is

estimated for the mental averaging performed on a

fluctuating reading. An allowance of 1.0% minimum

to 2.0% maximum of the reading is estimated for

calibrated manometer uncertainty and relocation of

the instrument after calibration. In addition, an

allowance of 0.5% minimum to 10.0% maximum of

the reading is estimated for instrument precision. No

allowance is included for yaw on the assumption that

the Pitot-static tube is aligned within 10 degrees of

streamlines. A combined uncertainty can be written

as:

ef (min) = [(0.02)2 + (0.01)2 + (0.005)2]0.5

= 0.0229

ef (max) = [(0.05)2 + (0.02)2 + (0.10)2]0.5

= 0.1136

T.4.9 Static pressure. An allowance of 1.0%

minimum to 5.0% maximum of the reading is

estimated for the mental averaging performed on a

fluctuating reading. An allowance of 1.0% minimum

to 2.0% maximum of the reading is estimated for

calibrated manometer uncertainty and relocation of

the instrument after . In addition, a tolerance of 10%

minimum to 20.0% maximum of the fan velocity

pressure should cover the influence of Pitot-static

tube yaw or velocity influence on static pressure taps

and other possible effects. A combined uncertainty

can be written as:

eg (min) = {(0.01)2 + (0.01)2 + (0.005)2 +

[0.1 Pv/(Ps2 - Ps1)]2}0.5

= {0.000225 + [0.1 Pv/(Ps2 - Ps1)]2}0.5

eg (max) = {(0.05)2 + (0.02)2 + (0.02)2 +

[0.2 Pv/(Ps2 - Ps1)]2}0.5

= {0.0033 + [0.2 Pv/(Ps2 - Ps1)]2}0.5

132

Where the denominator in the final term in each

equation will involve Ps2 or Ps5 and Ps1 or Ps4,

whichever are measured.

The estimated uncertainty range is based on an

allowance for fluctuation in the fan-system operation,

lack of ideal measurement locations, turbulence, and

the relocation of instrumentation after calibration.

T.5 Combined uncertainties

The uncertainties in the test performance are the

result of using various values, each of which contains

a probable uncertainty. The combined uncertainty for

each of the fan performance variables is given below.

T.5.1 Density. Air density involves the various

psychrometric measurements and the approximate

formula:

Where:

V = 1.0 - 0.378 {(pe/pb) - [(td - tw)/2700]}

For random and independant uncertainties in

products, the combined uncertainty is determined as

follows:

Δρ/ρ = {(Δ70.73/70.73)2 + (Δpb/pb)2 + (ΔV/V)2 +

(ΔR/R)2 + [Δtd/(td + 460)]2}0.5

Assuming Δ70.73 and ΔR are both zero:

eρ = (eb2 + ev

2 + ed2)0.5

It can be shown that:

ev2 = [(0.00000725 tw - 0.0000542) Δ(td - tw)]2

Where:

Δ(td - tw) = Absolute uncertainty in wet-bulb depression.

Other methods for determining density are assumed

to have equal accuracy.

T.5.2 Fan flow rate. Fan flow rate directly involves

the area at the flow measuring station, the Pitot

traverse, the square root of the pressure

measurement for flow, and the square root of the

density. Uncertainties in fan speed will produce a

first-power uncertainty in flow rate when making the

fan law conversions. Combining:

eQ = [ec2 + eA

2 (ef/2)2 + (eρ/2)2 + eN2]0.5

T.5.3 Fan static pressure. Fan static pressure

directly involves static pressure measurements.

Uncertainties in density will produce a first-power

uncertainty in fan static pressure while uncertainties

in fan speed will produce a second-power uncertainty

in fan static pressure when making fan law

conversions. Combining:

ep = [eg2 + eρ

2 + (2eN)2]0.5

ρ =+( )

70 73

460

. p VR t

b

d

Table T.1

Measurement Minimum Maximum

eb 0.003 0.007

ed** 0.005 0.020

eW 5/(td - tw) 10/(td - tw)

eN 0.005 0.010

eh 0.030 0.070

ec 0.015 0.075

eA 0.010 0.020

ef 0.0229 0.1136

eg {0.000225 + [0.1 Pv/(Ps2 - Ps1)]2}0.5 {0.0033 + [0.2 Pv/(Ps2 - Ps1)]2}0.5

* These uncertainties do not account for the effect of swirl at the fan inlet. This situation must be corrected in order

to produce acceptable fan-system performance (see Section 5).

** Based on absolute temperature

AMCA 203-90 (R2007)

133

In order to simplify the application of this uncertainty

analysis to the results of field tests, the above

equation was developed on the basis of tests in

which static pressure measurements are made at a

single plane, as would be the case in which a fan is

ducted on one side only. However, the equation is

reasonably accurate for all other fan-system

configurations.

Although in most cases the determination of fan static

pressure involves Pv1, the uncertainty in determining

Pv1 is not included in the above equation on the basis

that it normally has a very small effect on the overall

uncertainty in fan static pressure.

For purposes of this publication, eP is applied directly

to Psc, which may include System Effect Factors.

T.5.4 Fan power input. Fan power input directly

involves the power measurement; in addition, when

making fan law conversions, density has a first-power

effect and speed has a third-power effect on fan

power input. Combining:

eH = [eh2 + eρ

2 + (3eN)2]0.5

T.6 Summary

The minimum and maximum measurement

uncertainties (See Table T.1) were defined earlier in

Section T.4. Summarizing, the per unit uncertainties

are as shown in Table T.1.

The uncertainty calculations lead to absolute

uncertainties in fan flow rate, fan static pressure, and

fan power input that can be applied directly to the

corresponding test results. The uncertainty results

can then be plotted as rectangles around the test

point. Intersection of the rectangles with the quoted

fan performance within the limitations of a field test.

See the examples in Section T.7.

T.7 Examples

Two examples of the calculation of uncertainties and

the method of comparison with the quoted fan curve

are included in this section. Uncertainty calculations

and comparisons have been developed for Examples

2B and 2C of Annex A. Uncertainty calculations for

Example 2B utilize all minimum uncertainty

tolerances. Uncertainty calculations for Example 2C

utilize all maximum uncertainty tolerances. It would

be unlikely that any field installation would lend itself

to all minimum or all maximum measurement

tolerances. Agreement of the parties as to acceptable

measurement tolerances for a given installation

should be established prior to testing.

AMCA 203-90 (R2007)

134

AMCA 203-90 (R2007)

EXAMPLE 1: CALCULATION OF UNCERTAINTIES

IN TEST RESULTS BASED ON MINIMUM

MEASUREMENT UNCERTAINTY

TEST VALUES

Reference: Example 2B in Annex A

SITE MEASUREMENTS

td2 = 91.3°F

tw2 = 70.4°F

Ps1 = -11.4 in. wg

Ps2 = 0.1 in. wg

Pv3 = 1.24 in. wg

A2 = 1.40 ft2

A3 = 1.57 ft2

ρ2 = 0.0714 lbm/ft3

ρ3 = 0.0705 lbm/ft3

CONVERTED RESULTS

Qc = 7114 cfm

Psc = 11.42 in. wg

Hc = 18.90 hp

MEASUREMENT UNCERTAINTIES

Reference: Minimum values per Section T.6

eb = 0.003

ed = 0.005

ew = 5/(td2 - tw2)

eN = 0.005

eh = 0.030

ec = 0.015

eA = 0.010

ef = 0.0229

eg = {0.000225 + [0.1 Pv/(Ps2 - Ps1)]2}0.5

CALCULATIONS

Pv = Pv2

= Pv3 (A3/A2)2 (ρ3/ρ2)

= 1.24 (1.57/1.40)2 (0.0705/0.0714)

= 1.54 in. wg

eg = {0.000225 + [0.1 Pv/(Ps2 - Ps1)]2}0.5

= {0.000225 + [(0.1 × 1.54)/(0.1 + 11.4)]2}0.5

= 0.02011

ev2 = [(0.00000725 tw - 0.0000542) Δ(td - tw)]2

= [(0.00000725 × 70.4 - 0.0000542) 5]2

= 0.00000520

eρ = [eb2 + ev

2 + ed2)0.5

= (0.0032 + 0.00000520 + 0.0052)0.5

= 0.006261

eP = [eg2 + eρ

2 + (2eN)2]0.5

= [0.020112 + 0.0062612 + (2 × 0.005)2]0.5

= 0.0233

eQ = [ec2 + eA

2 + (ef/2)2 + (eρ/2)2 + eN2]0.5

= [0.0152 + 0.0102 + (0.0229/2)2 +

(0.006261/2)2 + 0.0052]0.5

= 0.0222

eH = [eh2 + eρ

2 + (3eN)2]0.5

= [0.0302 + 0.0062612 + (3 × 0.005)2]0.5

= 0.0341

ΔP = ePPsc

= 0.0233 × 11.42

= 0.27 in. wg

Psc + ΔP = 11.42 + 0.27

= 11.69 in. wg

Psc - ΔP = 11.42 - 0.27

= 11.15 in. wg

ΔQ = eQQc

= 0.0222 × 7114

= 158 cfm

Qc + ΔQ = 7114 + 158

= 7272 cfm

Qc - ΔQ = 7114 - 158

= 6956 cfm

ΔH = eHHc

= 0.0341 × 18.90

= 0.64 hp

Hc + ΔH = 18.90 + 0.64

= 19.54 hp

Hc - ΔH = 18.90 - 0.64

= 18.26 hp

135

QUOTED FANPERFORMANCECURVES

Q, FAN FLOW RATE

Q, FAN FLOW RATE

Ps,

FAN

STA

TIC

PR

ES

SU

RE

H, F

AN

PO

WE

R IN

PU

T

GRAPHICAL PRESENTATION

Psc

Psc - ∆P

Psc + ∆P

Qc - ∆Q

Qc - ∆Q

Qc + ∆Q

Qc + ∆Q

Qc

Qc

Hc + ∆H

Hc - ∆H

Hc

Figure T.1

TEST POINT

MINIMUM UNCERTAINTY RANGE

Qc = 7114 cfm

ΔQ = 158 cfm

Psc = 11.42 in. wg

ΔP = 0.27 in. wg

Hc = 18.90 hp

ΔH = 0.64 hp

AMCA 203-90 (R2007)

136

AMCA 203-90 (R2007)

EXAMPLE 2: CALCULATION OF UNCERTAINTIES

IN TEST RESULTS BASED ON MAXIMUM

MEASUREMENT UNCERTAINTIES

TEST VALUES

Reference: Example 2C in Annex A

SITE MEASUREMENTS

td3 = 86.5°F

tw3 = 75.5°F

Ps4 = -1.57 in. wg

Ps5 = 1.22 in. wg

Pv2 = 0.61 in. wg

CONVERTED RESULTS

Qc = 25964 cfm

Psc = 2.54 in. wg

Hc = 17.11 hp

MEASUREMENT UNCERTAINTIES

Reference: Maximum values per Section T.6

eb = 0.007

ed = 0.020

eW = 10/(td3 - tw3)

eN = 0.010

eh = 0.070

ec = 0.075

eA = 0.020

ef = 0.1136

eg = {0.0033 + [0.2 Pv/(Ps5 - Ps4)]2}0.5

CALCULATIONS

eg = {0.0033 + [0.2 Pv/(Ps5 - Ps4)]2}0.5

= {0.0033 + [(0.2 × 0.61)/(1.22 + 1.57)]2}0.5

= 0.07219

ev2 = [(0.00000725 tw - 0.0000542) Δ(td - tw)]2

= [(0.00000725 × 75.5 - 0.0000542) 10]2

= 0.0000243

eρ = (eb2 + ev

2 + ed2)0.5

= (0.0072 + 0.0000243 + 0.0202)0.5

= 0.02176

eP = [eg2 + eρ

2 + (2eN)2]0.5

= [0.072192 + 0.021762 + (2 × 0.010)2]0.5

= 0.0780

eQ = [ec2 + eA

2 + (ef/2)2 + (eρ/2)2 + eN2]0.5

= [0.0752 + 0.0202 + (0.1136/2)2

+ (0.02176/2)2 + 0.0102]0.5

= 0.0973

eH = [eh2 + eρ2 + (3eN)2]0.5

= [0.0702 + 0.021762 + (3 × 0.010)2]0.5

= 0.0792

ΔP = eP Psc

= 0.0780 × 2.54

= 0.20 in. wg

Psc + ΔP = 2.54 + 0.20

= 2.74 in. wg

Psc - ΔP = 2.54 - 0.20

= 2.34 in. wg

ΔQ = eQQc

= 0.0973 × 25964

= 2526 cfm

Qc + ΔQ = 25964 + 2526

= 28490 cfm

Qc - ΔQ = 25964 - 2526

= 23438 cfm

ΔH = eHHc

= 0.0792 × 17.11

= 1.36 hp

Hc + ΔH = 17.11 + 1.36

= 18.47 hp

Hc - ΔH = 17.11 - 1.36

= 15.75 hp

137

QUOTED FANPERFORMANCECURVES

Q, FAN FLOW RATE

Q, FAN FLOW RATE

Ps,

FAN

STA

TIC

PR

ES

SU

RE

H, F

AN

PO

WE

R IN

PU

T

Psc

Psc - ∆P

Psc + ∆P

Qc - ∆Q

Qc - ∆Q

Qc + ∆Q

Qc + ∆Q

Qsc

Qsc

Hc + ∆H

Hc - ∆H

Hc

GRAPHICAL PRESENTATION

Figure T.2

TEST POINT

MAXIMUM UNCERTAINTY RANGE

Qc = 25964 cfm

ΔQ = 2526 cfm

Psc = 2.54 in. wg

ΔP = 0.20 in. wg

Hc = 17.11 hp

ΔH = 1.36 hp

AMCA 203-90 (R2007)

138

AIR MOVEMENT AND CONTROLASSOCIATION INTERNATIONAL, INC.

30 West University DriveArlington Heights, IL 60004-1893 U.S.A.

E-Mail : [email protected] Web: www.amca.orgTel: (847) 394-0150 Fax: (847) 253-0088

The Air Movement and control Association International, Inc. is a not-for-profit international association of the world’s manufacturers of related air system equipment primarily, but limited to: fans, louvers, dampers, air curtains, airflow measurement stations, acoustic attenuators, and other air system components for the industrial, commercial and residential markets.


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