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The International Authority on Air System Components AIR MOVEMENT AND CONTROL ASSOCIATION INTERNATIONAL, INC. AMCA Publication 202-98 Troubleshooting
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The International Authority on Air System Components
AIR MOVEMENT AND CONTROLASSOCIATION INTERNATIONAL, INC.
AMCAPublication 202-98
Troubleshooting
AMCA PUBLICATION 202-98
Troubleshooting
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 Chief Staff Executive, Air Movement and Control
Association International, Inc. at 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.
Authority
AMCA Publication 202 was approved by the AMCA Membership on 13 February 1998.
AMCA 202 Review Committee
Jim Smith, Chairman Aerovent, A Twin City Fan Company
Mark Schultz American Fan Company
Tung Nguyen Emerson Ventilation Products
Scott Phillips The New York Blower Company
Tom Berger Pace Company, Division of York International
Bill Smiley The Trane Company
Paul R. Saxon AMCA Staff
Disclaimer
AMCA uses its best efforts to produce standards for the benefit of the industry and the public in light of available
information and accepted industry practices. However, AMCA does not guarantee, certify or assure the safety or
performance of any products, components or systems tested, designed, installed or operated in accordance with
AMCA 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 regarding
its standards, certification programs, or interpretations thereof. For information on procedures for submitting and
handling complaints, write to:
Air Movement and Control Association International
30 West University Drive
Arlington Heights, IL 60004-1893 U.S.A.
or
AMCA International, Incorporated
c/o Federation of Environmental Trade Associations
2 Waltham Court, Milley Lane, Hare Hatch
Reading, Berkshire
RG10 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. Procedure for Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
3. Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
4. System Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
5. Fan Manufacturer’s Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
5.1 Data required for analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
5.2 Probable manufacturer action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Annex A. Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Annex B. Insufficient Airflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Annex C. Airflow High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Annex D. Static Pressure Wrong . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Annex E. Power High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Annex F. Fan Does Not Operate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Annex G. Premature Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Annex H. Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
1
Troubleshooting
1. Introduction
After the installation of an air moving system is completed, a system sometimes fails to achieve its designed
performance.
This part of the AMCA Fan Application Manual will help you identify what is wrong and decide how to correct it.
2. Procedure for Troubleshooting
2.1 Look in the "Master Troubleshooting Appendices" for a subject which corresponds with the apparent problem.
2.2 Check each of the "Probable Causes" listed.
2.3 If the cause of the trouble is not found proceed through the "System Checklist" (see Section 4).
2.4 If the problem has still not been solved, it is now advisable to contact the representative of the fan manufacturer.
He should be given the results of the "System Checklist" and the additional information listed in Section 5.1.
2.5 The fan manufacturer or his representative will analyze the information submitted, as outlined in Section 5.2.
With this information and, if necessary, an on-site inspection, he may be able to explain why the system is not
achieving its design performance and may recommend changes in the system or the fan installation which will
overcome the problem.
3. Safety Precautions
Before checking the fan and system it will be necessary to shut down the fan. During inspection the fan must be
electrically isolated and all disconnect switches and other controls LOCKED in the "OFF" position. Where these
are in locations remote from the fan, prominent DO NOT START signs should also be in place.
CAUTION - Even when LOCKED out electrically, fans located outdoors or in a parallel or series fan system may
be subject to "wind-milling." Therefore, as an added precaution, the impeller should be secured to physically restrict
rotational movement.
4. System Checklist
Poor system performance may arise from a number of causes including:
• Improper installation or assembly of the fan
• Damage in handling or transit
• System design error
• Deterioration of the system
• Faulty controls
• Poor fan selection
• A combination of several factors.
A systematic check of the items listed here should help identify the problem - or problems - and allow suitable
corrective action to be taken.
AMCA INTERNATIONAL, INC. AMCA 202-98
SYSTEM CHECKLIST
A) While the impeller is coasting to a stop, see if it is rotating in the proper direction (see Figures 4.1, 4.2 and
4.3).
B) Make certain the impeller rotation is correct for the housing (guide vanes of vaneaxial and tubular centrifugal
fans) and not installed backwards (see Figures 4.1, 4.2, and 4.3).
Note: Tubeaxial fan rotation is the same as shown in Figure 4.2 except without the guide vanes.
2
AMCA 202-98
ROTATION
RADIALBLADE
BACKWARDINCLINED
AIRFOIL
RADIALTIP
BACKWARDCURVED
FORWARDCURVED
Figure 4.1 - Types of Centrifugal Fan Impellers
Note: Fan manufacturers describe the rotation of the fan impeller as being "clockwise" or "counterclockwise”.
• For AXIAL fans when viewing the INLET or OUTLET as specified by the Fan Manufacturer
• For CENTRIFUGAL fans when viewing the DRIVE SIDE (see AMCA Standard 99-2406)
• For TUBULAR CENTRIFUGAL fans when viewing the OUTLET (see AMCA Standard 99-2410).
3
AMCA 202-98
INLETGUIDE VANES
ROTATION ROTATION
OUTLETGUIDE VANES
AIRFLOW AIRFLOW
ROTATION
GUIDE
VANES AIRFLOW
Figure 4.2 - Vaneaxial Fan Impellers and Guide Vanes
Figure 4.3 - Tubular Centrifugal Impeller
4
C) If the fan is belt driven:
1) Are the drive pulley (Motor Sheave) and the driven pulley (Fan Sheave) in alignment? Improper
alignment of the sheaves can cause excessive power consumption (high amperage), squealing belts,
shortened belt and sheave life and high axial vibration.
Figure 4.4 - Sheave Alignment
2) Are the belts loose? Loose belts that flap or slip can cause excessive noise and vibration. Slipping belts
will also affect fan speed and reduce belt and sheave life.
Belts should be tensioned to the belt manufacturer's recommendations. Tension of the drive belts should
be adjusted for stretching after the first 48 hours of operation. Caution! Excessive belt tension will reduce
fan and motor bearing life.
3) Are the belts and/or sheaves worn? If so, an immediate replacement could save down time at a later
date. Where more than one belt is used, replace with a new set of matched belts.
Figure 4.5 - Belt Tension
D) Check the flow surfaces (passages between the inlets, impeller blades and inside of housing) for
cleanliness. A 2 mm (0.0625 in.) buildup of dirt on the flow surface could impair fan performance and/or
cause vibration.
E) Are there any gouges, tears, holes, erosion or corrosion in the impeller blades, rims or backplate: inlets
and/or housing? If so, report the approximate size and location to the fan manufacturer and discontinue
operation until repairs are made.
F) Is any foreign matter trapped in the impeller, housing or ductwork (loose insulation, papers, ice, etc.)? If so,
remove.
IMPROPER BELT TENSION PROPER BELT TENSION(SEE BELT MANUFACTURER’S SPECIFICATIONS)
IMPROPER SHEAVE ALIGNMENT PROPER SHEAVE ALIGNMENT
MOTOR MOTOR
FAN FAN
AMCA 202-98
5
G) Are coils, heaters, filters, ducts, etc. dirt laden? If so, clean or replace. Remove any non-essential
obstructions to airflow in elbows, shutters, transformations, dampers, bird-screens, etc. Verify that all
dampers (control, backdraft, fire, etc.) are adjusted to the proper settings.
H) Have all the parts supplied with the fan been installed?
I) Are there any obstructions to airflow near the fan inlets? Objects such as pipes, airflow measurement
stations, ductwork, columns, belt guards, belt drives, etc. could adversely affect the output of the fan. For
more information, see AMCA Publication 201 Fans and Systems.
J) Are the fan outlet connections correctly designed and installed? Duct takeoffs, or obstructions in the fan
outlet could adversely affect the output of the fan (see AMCA Publication 201).
K) See Figure 4.6A for typical centrifugal fan inlet-impeller relationships and Figure 4.6A for typical axial fan
housing-impeller relationships. A few simple measurements as indicated on these figures can tell the
manufacturer if a problem exists in this area. Note: several measurements should be taken around the
entire inlet/housing circumference to determine the average, maximum and minimum values.
Figure 4.6A - Typical Centrifugal Fan Inlet-Impeller Relationships
Figure 4.6B - Typical Axial Fan Housing-Impeller Relationships
C.
R.C. = RUNNING CLEARANCE(IMPELLER CENTERED IN HOUSING)
C. = VANE CLEARANCE
R.C.
I.G.
I.S.
I.S. = INLET SPACING
I.G. = INLET GAP
R.C. = RUNNING CLEARANCE(INLET CENTERED ON IMPELLER)
I.S. SHOULD BE SAME BOTH SIDESFOR DOUBLE WIDTH FAN
R.C.
I.S. I.S.
AMCA 202-98
6
L) On a double-width fan, is the approach to both inlets identical? Airflow should be symmetrical about the
centerline of the fan housing (see Figure 4.7A). Non-symmetrical airflow can lead to decreased air
performance. Belt drives, belt guards and motors can cause non-symmetrical airflow to the inlets if too
severely restricted (see AMCA Publication 201).
Figure 4.7A - Symmetrical Inlet Airflow
Figure 4.7B - Non-Symmetrical Inlet Airflow
Figure 4.8A - Turning Vanes in Elbow Adjacent to Centrifugal Fan
M) Are turning vanes installed in elbows that are too close to the fan inlet or discharge (see Figures 4.8A and
4.8B). Published pressure losses through elbows are based on a uniform velocity profile. Turning vanes
help achieve this uniform flow (see AMCA Publication 201).
N
R
ML
AIRFLOW
L NOT EQUAL TO MN NOT EQUAL TO R
P
P
LL
AIRFLOW
AMCA 202-98
7
Figure 4.8B - Turning Vanes in Elbow Adjacent to Axial Fan
N) If the fan is equipped with an inlet vane damper, check the operation as follows:
1) Do not rely on the control arm position alone for locating the position of the inlet vane damper blades
without first checking visually to see that the inlet vane damper position agrees with the position of the
control arm.
2) If the unit is a double-width fan equipped with inlet vanes or inlet vane damper control, both inlet vane
dampers must be synchronized (the inlet vane dampers must be in the same relative position with
respect to the impeller on both inlets). If the inlet vane dampers are not synchronized, there will be
unbalanced airflow between inlets resulting in deficient air performance, unbalanced thrust on the
bearings and/or a surge condition in the fan.
3) Make certain that inlet vane dampers are of the proper rotation with respect to the impeller. As the
vanes close they should cause the entering air to spin in the same direction as the impeller.
4) Are the inlet vane dampers correctly positioned for the design operating conditions? If not, the desired
pressure-volume of the fan will not be realized (see Figure 4.9).
Figure 4.9 - Typical Pressure-Volume Curve for Operation with Inlet Vane Damper Control
Percent of Free Delivery Volume
Per
cent
of N
o D
eliv
ery
Pre
ssur
e
100% Open
75% Open
50% Open
25% Open
100
80
60
40
20
0 20 40 60 80 100
AMCA 202-98
8
O) Inspect any ductwork or plenums approaching the fan inlets for the possibility of inducing swirl of air into the
inlet. Pre-swirl of air entering the fan inlet can reduce the fan performance (see Figures 4.10A and 4.10B).
(See AMCA Publication 201.)
P) After completing the above steps and making sure the fan and system are safe to start, remove all DO NOT
START signs on disconnect switches and override systems and put the unit back into operation.
Q) Inspect the entire system including the fan, fan plenum and all ductwork for significant air leaks. Air leaks
may be detected by sound, smoke, feel, soapy solution, etc. Some common air leak sources are: access
doors, coils, duct seams, fan outlet connection, etc. Significant air leaks must be sealed.
5. Fan Manufacturer's Analysis
If the cause of the trouble has still not been found after completing the "System Checklist," the fan manufacturer
should be consulted.
The fan manufacturer will review the information provided concerning the system and recommend an appropriate
course of action.
5.1 Data required for analysis
To make a complete analysis of the problem, in addition to the results of the "System Checklist," the manufacturer
will need:
A) Complete plans (drawings) including all ductwork, location, size, model and manufacturer of all fans,
motors, coils, dampers, etc. with all pertinent dimensions for the complete system as actually installed.
B) If the fan/air handling system fails to achieve the design performance, the measured performance and the
design performance figures should be supplied.
C) A copy of the system design calculations.
D) A copy of the specifications and any addendums.
IMPELLERROTATION
IMPELLERROTATION
AIR SWIRL IN SAME DIRECTIONAS IMPELLER ROTATION
AIR SWIRL IN OPPOSITE DIRECTIONTO IMPELLER ROTATION
Figure 4.10A - Pre-Rotation Figure 4.10B - Counter-Rotation
AMCA 202-98
9
E) If a separate air performance test has been conducted on the installed fan, a statement of measured fan
performance along with a copy of the test data, the type of test and instrumentation, and the measurement
location of the airflow rate and pressure determinations should be supplied. A statement of fan performance
should contain:
1) Fan total pressure (Pt) rise or fan static pressure (Ps)
2) Airflow rate (Q)
3) Power (H)
4) Fan speed (N)
5) Air density (ρ)
5.2 Probable manufacturer action
Among other actions, the fan manufacturer will:
A) Assess the probable accuracy of the field performance measurements (see AMCA Publication 203 FieldPerformance Measurements of Fan Systems).
B) Examine the system drawings (plans) for any System Effect losses (see AMCA Publication 201) which were
not allowed for in the system design calculations or the original fan selection.
C) Reassess the fan performance, accounting for System Effect losses established in step B to the designed
fan/system performance (see Figure 5.1).
D) Check whether the fan selection is correct for the application.
Figure 5.1
FAN OPERATING POINTW/SYSTEM EFFECT
SYSTEM EFFECT
DUCT SYSTEM CURVE
DESIGN FAN OPERATING POINT
FAN CATALOGPRESSURE-VOLUME CURVE
THEORETICAL PRESSURE-VOLUMECURVE ACCOUNTING FOR SYSTEM EFFECTLOSSES (FIELD PERFORMANCE MEASUREMENTSTO BE COMPARED AGAINST THIS CURVE).
DESIGN VOLUME
DE
SIG
N P
RE
SS
UR
E
AMCA 202-98
10
The information obtained through the checklists in this manual should help in defining the necessary corrective
action.
In most cases, if the troubleshooting procedure has been followed carefully and impartially it will be apparent
whether the system has been built and installed in accordance with the design drawings, whether the fan was
properly selected and suitable allowances made for the appropriate System Effect Factors, or whether the fan is
not performing up to its published ratings.
6. Conclusion
By intelligent application of the procedures outlined in this manual it should be possible to find the cause of a
performance problem in any air moving system.
Identification of a problem associated directly with the fan may require the assistance of the fan manufacturer.
Recognition of the cause of the trouble will usually be a major step toward curing it. Corrective measures may
include alterations to the system, modifications to the fan outlet or inlet connections, adjustments to the fan, etc.
In many cases an increase in the fan speed may be decided upon but it is extremely important that the fan shall
not be operated above its cataloged maximum speed or the maximum speed recommended by the
manufacturer. Excessive speed may result in catastrophic impeller failure. If a speed increase proves to be
an acceptable alternative, then the motor should also be checked for its capacity to handle the increased fan power.
AMCA 202-98
11
MASTER TROUBLESHOOTING APPENDICES
Annex A. Noise
SOURCE PROBABLE CAUSE
A-1 IMPELLER HITTING INLET OR HOUSING . . . . . . . . . . . . . a. Impeller not centered in inlet or housing.
b. Inlet or housing damage.
c. Crooked or damaged impeller.
d. Shaft loose in bearing.
e. Impeller loose on shaft.
f. Bearing loose in bearing support.
g. Bent shaft.
h. Misaligned shaft and bearings.
A-2 IMPELLER HITTING CUTOFF . . . . . . . . . . . . . . . . . . . . . . . a. Cutoff not secure in housing.
b. Cutoff damaged.
c. Cutoff improperly positioned.
d. Impeller improperly positioned.
A-3 DRIVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Sheave not tight on shaft (motor or fan).
b. Belts hitting belt tube or belt guard.
c. Belts too loose. Adjust for belt
stretching after 48 hours of operation.
d. Belts too tight.
e. Belts wrong cross-section.
f. Belts not "Matched" in length on
multi-belt drive.
g. Variable pitch sheaves not
adjusted so each groove has same
pitch diameter (multi-belt drive).
h. Misaligned sheaves.
i. Belts worn.
j. Motor, motor base or fan not
securely anchored.
k. Belts oily or dirty.
l. Improper drive selection.
m. Loose key.
A-4 COUPLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Coupling unbalanced, misaligned, loose
or may need lubricant.
b. Loose key.
A-5 BEARING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Defective bearing.
b. Needs lubrication.
c. Loose on bearing support.
d. Loose on shaft.
e. Seals misaligned.
f. Foreign material inside bearing.
g. Worn bearing.
h. Fretting corrosion between inner race
and shaft.
i. Bearing not sitting on flat surface.
A-6 SHAFT SEAL SQUEAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Needs lubrication.
b. Misaligned.
c. Bent shaft.
d. Bearing loose on support.
AMCA 202-98
12
A-7 IMPELLER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Loose on shaft.
b. Defective impeller. DO NOT
OPERATE FAN. LOCK OUT
THE FAN ELECTRICALLY AND
CONTACT THE MANUFACTURER.
c. Unbalance.
d. Coating loose.
e. Worn as result of abrasive or corrosive
material moving through airflow
passages.
f. Blades rotating close to structural
member.
g. The number of blades may coincide
with an equal number of structural
members.
h. Loose key.
A-8 HOUSING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Foreign material in housing.
b. Cutoff or other housing part loose
(rattling during operation).
A-9 MOTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Lead-in cable not secure.
b. AC hum in motor or relay.
c. Starting relay chatter.
d. Noisy motor bearings.
e. Single phasing a three phase motor.
f. Low voltage.
g. Cooling fan striking shroud.
h. Poor motor/inverter match, more
noticeable at low speeds.
A-10 SHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Bent
b. Undersized. May cause noise at
impeller, bearings or sheave.
A-11 HIGH AIR VELOCITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Ductwork too small for application.
b. The installed fan may be too small for
the application.
c. Registers or grilles too small for
application.
d. Heating or cooling coil with
insufficient face area for application.
A-12 OBSTRUCTION IN HIGH VELOCITY
AIR STREAM MAY CAUSE RATTLE, OR
PURE TONE WHISTLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Dampers.
b. Registers.
c. Grilles.
d. Sharp elbows.
e. Sudden expansion in ductwork.
f. Sudden contraction in ductwork.
g. Turning vanes.
A-13 PULSATION OR SURGE . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Restricted system causes fan to
operate at poor point of rating.
b. Fan too large for application.
c. Ducts vibrate at same frequency as fan
pulsations.
d. Rotating stall.
AMCA 202-98
13
e. Inlet vortex surge.
f. Distorted inlet airflow.
A-14 AIR LEAKS AND/OR OBSTRUCTED FLOW . . . . . . . . . . . . a. Air leaks in ductwork.
1) Bad joint connections;
2) Holes or tears;
3) Obstructions inside duct.
b. Fins on coils.
c. Registers or grilles.
A-15 RATTLES AND/OR RUMBLES . . . . . . . . . . . . . . . . . . . . . . . a. Vibrating ductwork.
b. Vibrating cabinet parts.
c. Vibrating parts not isolated from
building.
AMCA 202-98
14
Annex B. Insufficient Air Flow
SOURCE PROBABLE CAUSE
B-1 FAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Impeller installed backwards.
b. Impeller running backwards.
c. Impeller blade angle setting.
d. Cutoff missing or improperly installed.
e. Impeller not centered with inlet collar(s).
f. Fan rpm below design:
1) Incorrect sheave or sheave setting;
2) Incorrect motor rpm;
3) Low voltage to motor;
4) Speed controller set too low;
CAUTION! DO NOT INCREASE FAN
SPEED BEYOND THE FAN
MANUFACTURER'S
RECOMMENDATIONS. ALSO, WHEN
INCREASING FAN SPEED, MONITOR
MOTOR AMPS SO AS NOT TO
EXCEED MOTOR NAMEPLATE AMPS.
g. Impeller/inlet dirty or clogged.
h. Improper running clearance.
i. Improper inlet cone to impeller fit.
j. Improperly set inlet vane or damper.
B-2 DUCT SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Actual system is more restrictive (more
resistance to airflow) than expected.
b. Dampers closed.
c. Registers closed.
d. Air leaks in supply ducts.
e. Insulating duct liner loose.
B-3 FILTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Dirty or clogged.
b. Replacement filter with greater than
specified pressure drop.
B-4 COILS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Dirty or clogged.
b. Incorrect fin spacing.
B-5 RECIRCULATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .a. Internal cabinet air leaks in bulkhead
separating fan outlet (pressure zone)
from inlet(s) (suction zone).
b. Air leaks around fan outlet at
connection through cabinet bulk-head.
B-6 OBSTRUCTED FAN INLETS . . . . . . . . . . . . . . . . . . . . . . . .a. Elbows, cabinet walls or other
obstructions restrict airflow. Inlet
obstructions cause more restrictive
systems but do not cause increased
negative pressure readings near the fan
inlet(s) (see System Effects in AMCA
Publication 201). Fan speed may be
increased to counteract the effect of
restricted fan inlet(s).
CAUTION! DO NOT INCREASE FAN
SPEED BEYOND THE FAN MANUFA-
CTURER'S RECOMMENDATIONS.
ALSO, WHEN INCREASING FAN
AMCA 202-98
15
SPEED, MONITOR MOTOR AMPS SO
AS NOT TO EXCEED MOTOR
NAMEPLATE AMPS.
B-7 NO STRAIGHT DUCT AT FAN OUTLET . . . . . . . . . . . . . . . a. Fans which are normally used in duct
system are tested with a length of
straight duct at the fan outlet. If there is
no straight duct at the fan outlet,
decreased performance may result. If it
is not practical to install a straight
section of duct at the fan outlet, the fan
speed may need to be increased to
overcome this pressure loss (see
System Effects in AMCA Publication
201).
CAUTION! DO NOT INCREASE FAN
SPEED BEYOND THE FAN MANUFA-
CTURER'S RECOMMENDATIONS.
ALSO, WHEN INCREASING FAN
SPEED, MONITOR MOTOR AMPS SO
AS NOT TO EXCEED MOTOR
NAMEPLATE AMPS.
B-8 OBSTRUCTION IN HIGH VELOCITY AIR STREAM . . . . . . a. Obstruction near fan outlet or inlet(s).
b. Sharp elbows near fan outlet or inlet(s).
c. Improperly designed turning vanes.
d. Projections, dampers or other
obstruction in a part of the system
where air velocity is high.
AMCA 202-98
16
Annex C. Airflow High - (Too Much Airflow)
SOURCE PROBABLE CAUSE
C-1 SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Oversized ductwork.
b. Access door open.
c. Registers or grilles not installed.
d. Dampers set to by-pass coils.
e. Filter(s) not in place.
f. System resistance low.
C-2 FAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Fan speed too fast.
b. Improper impeller blade angle.
AMCA 202-98
17
Annex D. Static Pressure Wrong
SOURCE PROBABLE CAUSE
D-1 SYSTEM, FAN OR INTERPRETATION
OF MEASUREMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GENERAL DISCUSSION:
The velocity pressure at any point of
measurement is a function of the velocity of
the air and its density.
The static pressure at a point of
measurement in the system is a function of
the system design (resistance to airflow), air
density and the amount of air flowing through
the system.
The static pressure measured in a "loose" or
oversized system will be less than the static
pressure in a "tight" or undersized system for
the same airflow rate.
In most systems, pressure measurements
are indicators of how the installation is
operating. These measurements are the
result of airflow and as such are useful
indicators in defining system characteristics.
Field static pressure measurements rarely
correspond with laboratory static pressure
measurements unless the fan inlet(s) and
fan outlet conditions of the installation are
exactly the same as the inlet(s) and outlet
conditions in the laboratory.
Also see D-2 through D-6, E-2, F-1 and G-1
for specific cases.
Static Pressure Low, Airflow Correct
D-2 GAS DENSITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressures will be less with high
temperature gases or at high altitudes.
Static Pressure Low, Airflow High
D-3 SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . System has less resistance to airflow
than expected. This is a common
occurrence. Fan speed may be reduced to
obtain desired airflow rate. This will reduce
power consumption (operating cost).
Static Pressure Low, Airflow Low
D-4 SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Fan inlet(s) and/or outlet conditions not
same as tested. See System EffectFactors, in AMCA Publication 201.
AMCA 202-98
18
D-5 FAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Impeller installed backwards.
b. Impeller running backwards.
c. Improper impeller blade angle.
d. Cutoff missing or improperly installed.
e. Impeller not centered with inlet collar(s).
f. Fan speed too slow.
g. Impeller/inlet dirty or clogged.
h. Improper running clearance.
i. Improper inlet cone to impeller fit.
j. Improperly set inlet vanes or damper.
Static Pressure High, Airflow Low
D-6 DUCT SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Actual system is more restrictive (more
resistance to airflow) than designed.
b. Dampers closed.
c. Registers closed.
d. Insulating duct liner loose.
D-7 FILTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Dirty or clogged.
b. Replacement filter with greater than
specified pressure drop.
D-8 COILS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Dirty or clogged.
b. Fin spacing too close.
AMCA 202-98
19
Annex E. Power High
SOURCE PROBABLE CAUSE
E-1 FAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Backward Inclined impeller installed
backwards.
b. Fan speed too high.
c. Forward Curve or Radial Blade
impeller operating below design
pressures.
d. Incorrect impeller blade angle.
E-2 SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Oversized ductwork.
b. Face and bypass dampers
oriented so coil dampers are open at
same time bypass dampers are open.
c. Filter(s) left out.
d. Access door open.
Note: The causes listed under E-2 pertain
primarily to radial blade, radial tip and
forward curve centrifugal fans, i.e., fans that
exhibit rising power curves. Normally,
backward inclined, backward curve or
backward inclined airfoil centrifugal fans and
axial flow fans do not fall into this category.
E-3 GAS DENSITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .a. Calculated power requirements based
on light gas (e.g. high temperature) but
actual gas is heavy (e.g. cold start-up).
E-4 FAN SELECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .a. Fan not selected at efficient point of
rating.
AMCA 202-98
20
Annex F. Fan Does Not Operate
SOURCE PROBABLE CAUSE
F-1 ELECTRICAL OR MECHANICAL . . . . . . . . . . . . . . . . . . . . . Mechanical and electrical problems are
usually straight-forward and are normally
analyzed in a routine manner by service
personnel. In this category are such items:
a. Blown fuses.
b. Broken belts.
c. Loose pulleys.
d. Electricity turned off.
e. Impeller touching housing.
f. Wrong voltage.
g. Motor too small and overload protector
has broken circuit.
h. Low voltage, excessive line drop or
inadequate wire size.
i. Load inertia too large for motor.
j. Seized bearing.
AMCA 202-98
21
Annex G. Premature Failure
SOURCE PROBABLE CAUSE
G-1 BELTS, BEARINGS, SHEAVES IMPELLERS
HUBS, ETC.GENERAL DISCUSSION . . . . . . . . . . . . . . . . . Each fan component is designed to operate
satisfactorily for a reasonable lifetime. Fans
intended for heavy duty service are made
especially for that type of service. For
example, Class I fans are intended for
operation below certain limits of pressure
and outlet velocity. Class II fans are
designed for higher operating limits (see
AMCA Standard 99-2408). Not all
components are limited by the same factors,
e.g. limiting factors may be power, RPM,
temperature, impeller tip speed, torque,
corrosive atmospheres, expected life, etc.
Also see A-2, A-5, A-6, A-7.
G-2 COUPLINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Coupling unbalanced, misaligned, loose
or may need lubricant.
b. Loose key.
G-3 SHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Bent.
b. Undersized.
G-4 BEARINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Over-lubrication or under- lubrication.
b. Locking collar or set screw loose.
c. Excessive belt tension.
d. False brinelling.
e. Wrong lubricant.
f. Undersized shaft.
G-5 DRIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Over-tensioned or under-tensioned belts.
b. Mismatched belts on multi-belt drive.
c. Misalignment of motor and fan sheaves.
d. Excessive start-stop cycles.
e. Set screw on sheave loose.
AMCA 202-98
22
Annex H. Vibration
AERODYNAMIC VIBRATION (PULSATION)
SOURCE PROBABLE CAUSE
H-1 AIRSTREAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Operating fan left of peak in unstable
(stall) region.
b. Poor inlet conditions which generate air
turbulence.
1. Partially obstructed inlet(s).
2. Sharp elbow at fan inlet(s) and/or
outlet.
c. System pulsation which is transmitted to
the fan.
d. Blade Pass frequency -- number of
blades x fan RPM.
e. Guide vane frequency -- number of
vanes x fan RPM.
f. Fan support frequency -- motor or
bearing supports, belt tube, on axial
fans.
MECHANICAL VIBRATION
H-2 UNBALANCED IMPELLERS . . . . . . . . . . . . . . . . . . . . . . . . a. Material build-up on impeller.
b. Impeller components subject to
abrasion, corrosion or impact.
c. Moisture inside hollow airfoil blades.
d. Lost balance weight.
e. Excessive temperature.
f. Impeller (blades) not tracking evenly.
g. Eccentricity:
1. Bore off center.
2. Bore on angle (see H-2.f)
h. Improper key-to-keyway length.
i. Impeller rubbing stationary equipment.
j. Shaft seal rub.
k. Inverter drives.
l. Motor torque pulses (on single phase
motors).
H-3 DRIVE OR COUPLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Alignment:
1. Improper assembly.
2. Shift during handling or shipment.
b. Worn, loose, or mismatched belts.
c. Eccentric sheaves or couplings.
d. Belt resonance.
e. Worn or chipped sheaves.
f. Improper key-to-keyway length.
g. Unbalanced sheave(s) or coupling.
H-4 LOOSE FASTENERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Impeller set screws.
b. Bearing set screws.
c. Drive component set screws.
d. Fan mounting bolts.
e. Bearing bolts.
f. Motor bolts.
AMCA 202-98
23
H-5 FAN SUPPORT STRUCTURE . . . . . . . . . . . . . . . . . . . . . . . a. Support structure natural frequencies.
b. Insufficient mass or stiffness.
c. Large unsupported mass.
d. Lack of lateral support, particularly with
fans mounted on isolators.
e. Fan skewed (bolted down to uneven
surface).
f. Broken support members.
g. Short-circuited or improperly adjusted
isolators.
h. Fan (mounted on isolators) with rigid
inlet(s) and outlet connections.
H-6 SHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Bent.
b. Undersized.
H-7 BEARINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Misalignment.
b. Worn out; loose.
c. Too much, too little, or incorrect
lubricant.
H-8 BACKGROUND EXCITATION
(FLANKING TRANSMISSION) . . . . . . . . . . . . . . . . . . . . . . .a. Interconnected piping.
b. Heavy machinery transmitting vibration
through foundation.
c. Fan(s) mounted on floating roofs.
d. Wind-loading of fan mounted on
isolators.
ELECTRICALLY INDUCED VIBRATION
H-9 ELECTRIC MOTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a. Loose stator laminations.
b. Broken rotor bar.
c. Stator problems.
d. Phase unbalance.
e. Eccentric rotor.
f. Capacitor-start motor causes "shudder"
during coast-down.
AMCA 202-98
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.