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Installation, Operation and Maintenance Manual IOM ACAQ Group: Chiller Part Number: 074640501 Effective: February 1998 Supersedes: None © 1998 McQuay International Air-Cooled Condensers Type ACS 010 Through ACS 100 Type ACD 045 Through ACD 210 Type AQS 020 Through AQS 085 Type AQD 040 Through AQD 170
Transcript
Page 1: Air-Cooled Condensers - Daikin Appliedlit.daikinapplied.com/bizlit/literature/lit_ch_ac/IMOM/...6 Air-Cooled Condensers IOM ACAQ Refrigerant Piping Figure 2 illustrates a typical piping

Installation, Operation and Maintenance Manual IOM ACAQ

Group: Chiller

Part Number: 074640501

Effective: February 1998

Supersedes: None

© 1998 McQuay International

Air-Cooled Condensers

Type ACS 010 Through ACS 100Type ACD 045 Through ACD 210

Type AQS 020 Through AQS 085Type AQD 040 Through AQD 170

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2 Air-Cooled Condensers IOM ACAQ

Table of Contents

Introduction............................................................................................................3

Installation..............................................................................................................3

Unit Location...............................................................................................................................3Sound Vibration ...........................................................................................................................3Walls or Obstructions...................................................................................................................4Multiple Units..............................................................................................................................5Units in Pits .................................................................................................................................5Decorative Fences ........................................................................................................................5

Refrigerant Piping..................................................................................................6

Refrigerant Piping........................................................................................................................7Discharge Lines ...........................................................................................................................7

Electrical Wiring ....................................................................................................8

Operation..............................................................................................................17

Start-Up .....................................................................................................................................17Discharge Gas Pulsation.............................................................................................................17Low Ambient Operation Head Pressure Control .........................................................................17Fan Cycling ...............................................................................................................................17Fan Cycling Head Pressure Controls ..........................................................................................18SpeedTrol ..................................................................................................................................18

Maintenance.........................................................................................................18

Cleaning Instructions .................................................................................................................18

1998 McQuay International"Illustrations cover the general appearance of McQuay International products at the time of publication and we reserve the right to make changes in design and

construction at anytime without notice"

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IOM ACAQ Air-Cooled Condensers 3

Introduction

Carefully check each shipment against the bill of lading and account for all items. Report anyshortage or damage to the delivering carrier.

Be careful when uncrating, to prevent damage. Heavy equipment should be left on units shippingbase until it has been moved to the final location.

This equipment must be installed in accordance with accepted industry standards. Failure to meetthe following conditions may void the warranty:

1. System piping must be installed following industry standards for good piping practices.

2. Inert gas must be charged into piping during welding.

3. System must be thoroughly leak checked and evacuated before initial charging. High vacuumgauge capable of reading microns is mandatory. Dial indicating pressure gauges are notacceptable.

4. Power supply to system must meet the following conditions:

§ Voltage for 208/230 motors not less than 195 volts or more than 253 volts.

§ All other voltages must be within 10% of nameplate ratings.

§ Phase imbalance not to exceed 2%.

5. All controls and safety switch circuits properly connected per wiring diagram.

6. Factory installed wiring must not be changed without written factory approval.

7. Relief valves must meet all code requirements.

Installation

Unit LocationUnits are designed for outdoor application and may be mounted on a roof or concrete slab (groundlevel installation). Install roof mounted units on steel channels or an I-beam frame to support theunit above the roof. Use of vibration pads or isolators is recommended. The roof must be strongenough to support the weight of the unit. For ground level installation, mount units on a one-piececoncrete slab with footings extending below the frost line. Be certain concrete slabs are installedlevel and are properly supported to prevent settling. Locate the condenser far enough away fromany wall or other obstruction to provide sufficient clearance for air entrance. Do not attachductwork to the coil inlet or fan outlet. Avoid air recirculation conditions that may be caused bysight screening, walls, etc. and keep unit fan discharge away from any building air intakes. Do notinstall unit where exhaust or ventilation equipment will affect entering air temperature or foul coils.

Sound VibrationInstall units away from occupied spaces, utility areas, corridors and auxiliary spaces to reduce thetransmission of sound and vibration to occupied spaces. The refrigerant piping should be flexibleenough to prevent the transmission of noise and vibration from the unit into the building. If therefrigerant lines are to be suspended from the structure of the building, use isolation hangers toprevent the transmission of vibration. Where piping passes through a wall, pack fiberglass andsealing compound around the lines to minimize vibration and retain flexibility. The unit must besecured in its final location. Holes are provided in the base runner for this purpose.

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Figure 1, Unit Rigging

Walls or ObstructionsLocate the unit to ensure air may circulate freely and not be recirculated. For proper air flow andaccess all sides of the unit must be at least the total width of condenser away from any wall orobstruction. Increase thisdistance whenever possible. Besure enough room is left formaintenance through accessdoors and panels. Overheadobstructions are not permitted.When enclosed by three wallsthe unit must be installed asindicated for units in a pit.

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IOM ACAQ Air-Cooled Condensers 5

Multiple UnitsFor units placed side by side, theminimum distance between unitsis the width of the largest unit. Ifunits are placed end to end, theminimum distance between unitsis 4 feet.

Units in PitsThe top of the unit should belevel with the top of the pit, andside distance increased to at leasttwice the width of condenser. Ifthe top of the unit is not levelwith the top of pit, dischargecones or stacks must be used to raise discharge air to the top of the pit. This is a minimumrequirement.

Decorative FencesFences must have 50% freearea, with 1 foot undercut, atleast the width of condenserminimum clearance, and mustnot exceed the top of unit. Ifthese requirements are notmet, unit must be installed asindicated for "Units in pits".

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Refrigerant Piping

Figure 2 illustrates a typical piping arrangement involving a remote condenser located at a higherelevation, as commonly encountered when the condenser is on a roof and the compressor andreceiver are on grade level or in a basement equipment room. In this case, the design of thedischarge line is very critical. If properly sized for full load condition, the gas velocity might be toolow at reduced loads to carry oil up through the discharge line and condenser coil. Reducing thedischarge line size would increase the gas velocity sufficiently at reduced load conditions; however,when operating at full load, the line would be greatly undersized, and thereby create an excessiverefrigerant pressure drop. This condition can be overcome in one of two following ways:

1. The discharge line may be properly sized for the desired pressure drop at full load conditionsand an oil separator installed at the bottom of the trap in the discharge line from thecompressor.

2. A double riser discharge line may be used as shown in Figure 3. Line "A" should be sized tocarry the oil at minimum load conditions and the line "B" should be sized that at full loadconditions both lines would have sufficient flow velocity to carry the oil to the condenser.

For more complete information, see the ASHRAE Handbook on Systems.

Be aware of the following when fabricating piping:

• All oil traps are to be as short in radius as possible. The trap may be fabricated using three 90degree ells.

• Use pressure relief valves at the condenser to protect the coil.

• Use a drain line check valve when the condenser is at a lower temperature than the receiver.

Figure 2, Typical Piping Arrangement

Figure 3, Double Riser Discharge Piping

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IOM ACAQ Air-Cooled Condensers 7

Refrigerant PipingInstall piping according to standard accepted refrigeration practice. See Table 1 and Table 2 fordischarge and liquid drain line sizes for remote condenser connections. Use only refrigeration gradecopper tubing and put dry nitrogen through lines while brazing.

CAUTION

Do not use soft solder joints. Do not leave dehydrated piping or components open to theatmosphere any longer than is absolutely necessary.

Discharge LinesDesign discharge lines to ensure refrigerant pressure drop is minimized (high pressure losses causeincreased compressor horsepower per ton of refrigerant) and a sufficiently high gas velocity to carryoil through to the condenser coil and receiver at all loading conditions is maintained.

Table 1, Tons of Refrigeration

Line Size Discharge Line Drain Line

Type L R-22 R-404A, R-507 Velocity 100 FPM

Copper Sat. Suction Temp. (°F) Sat. Suction Temp. (°F) Refrigerant

OD -40 0 40 -40 0 40 R-22 R-502

1/2 0.75 0.8 0.85 0.56 0.63 0.7 2.3 1.5

5/8 1.4 1.5 1.6 1.0 1.2 1.3 3.7 2.3

7/8 3.7 4.0 4.2 2.7 3.1 3.4 7.8 4.9

1 1/8 7.5 8.0 8.5 5.5 6.3 7.0 13.2 8.3

1 3/8 13.1 14.0 14.8 9.6 10.9 12.1 20.2 12.6

1 5/8 20.7 22.0 23.4 15.2 17.2 19.1 28.5 17.9

2 1/8 42.8 45.7 48.5 31.4 35.6 39.5 49.6 31.1

2 5/8 75.4 80.4 85.4 55.3 62.8 69.5 76.5 48.0

3 1/8 120.2 128.2 136.2 87.9 99.8 110.5 109.2 68.4

3 5/8 178.4 190.3 202.1 130.5 148.1 164.0 147.8 92.6

4 1/8 251.1 267.8 284.4 183.7 208.4 230.9 192.1 120.3

Notes:1. Source: ASHRAE Refrigeration Handbook:2. Line sizes based on pressure drop equivalent to 1 'F per 100 equivalent feet3. Values in Table are based on 1051F condensing temperature. Multiply Table capacities by the factors in Table 2 for other

condensing temperatures.4. If subcooling is substantial or the line is short, a smaller line size may be used. Applications with very little subcooling or very

long lines may require larger sizes.

Table 2, Condensing Temperature Correction Factor

Condensing Discharge Line

Temperature R-22 R-404, R-507

90 0.88 0.91

100 0.95 -0.97

110 1.04 1.02

120 1.10 1.08

130 1.18 1.16

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Electrical Wiring

All electrical wiring must be installed according to the National Electrical Code, local codes andregulations. Use copper conductors only. Provide overcurrent protection for the fan motors. Allstandard motors have internal inherent overload protectors, allowing contactors to be used instead ofstarters requiring thermal protectors.

WARNING

There may be more than one source of electrical current in this unit. Do not servicebefore disconnecting all power supplies.

All condensers are furnished with either single-phase or three-phase fan motors which are identifiedby the unit dataplate. Electrical leads from each motor terminate at the unit junction box. Fieldconnections must be made from these leads in accordance with local, state and national codes. Themotors are wired into a common junction box. Where fan cycling is furnished and factory installed,the motors are completely wired through the control and to the contactors. Check motors for properrotation and be sure motor voltage and control voltage agree with electric services furnished.

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IOM ACAQ Air-Cooled Condensers 9

Figure 4, Typical Two - Four Fan Wiring With Fan Control

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Figure 5, Typical Four - Eight Fan Wiring With Fan Control

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IOM ACAQ Air-Cooled Condensers 11

Figure 6, Typical Five Fan Wiring With Fan Control

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Figure 7, Typical Six Fan Wiring With Fan Control

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IOM ACAQ Air-Cooled Condensers 13

Figure 8, Typical Ten Fan Wiring With Fan Control

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Figure 9, Typical Twelve Fan Wiring With Fan Control

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IOM ACAQ Air-Cooled Condensers 15

Figure 10, Typical Six Fan Wiring With Individual Contactor Control

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Figure 11, Typical Twelve Fan Wiring With Individual Contactor Control

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IOM ACAQ Air-Cooled Condensers 17

Operation

Start-UpCheck for proper fan rotation. Air is drawn through the coil on all units. Be sure the fans turnfreely. Rotation of the motors and blades should be in a "clock-wise" direction looking at the unitfrom the blade side. On three phase units, it may be necessary to reverse two of the three powerleads to the unit.

Discharge Gas PulsationGas pulsations in a refrigeration system are most commonly associated with the compressor andconnecting discharge piping. Variations in the system piping configuration, line sizing, operatingpressures and compressor and component mounting all contribute to the presence and magnitude ofthese pulsations. The vibration and movement of components caused by the pulsations may result inline breakage or damage to the condenser. In order to eliminate discharge pulsations and thepotential for related condenser damage, install a discharge muffler in the refrigeration piping.Follow the recommendations of the compressor or muffler manufacturer when selecting thesecomponents.

Low Ambient Operation Head Pressure ControlThe capacity of an air-cooled condenser varies with the difference between the entering air dry bulbtemperature and the condensing temperature of the refrigerant. Since air temperature in someregions varies from summer to winter, the condensing temperature must be kept high enough toensure proper operation of the refrigerant expansion valve during low ambient operation, and alsoallow enough capacity to ensure excessively high condensing temperatures do not occur during highambient conditions.

The low limit of the head pressure is dependent upon the required pressure drop across thethermostatic expansion valve. For normal air conditioning applications, maintain head pressureabove a condensing temperature corresponding to 90° F. This corresponds to a normal lower limit ofabout 60°F ambient air. When operation is required below 60°F ambient air temperature, additionalhead pressure control will be required.

Fan CyclingA decrease in ambient air temperature results in a capacity increase in the air-cooled condenser.This capacity increase is directly proportional to the temperature difference between the condensingtemperature and the temperature of the ambient air entering the condenser. Air-cooled condensersare often required to operate over a wide range of ambient air temperatures and variable loadingconditions, provisions must be made to maintain the overall system balance. Low head pressurescause poor expansion valve operation and poor system operation.

The cycling of condenser fans provides an automatic means of maintaining head pressurecontrol, within reasonable limits, at lower ambient air temperatures. A fan cycling control systemallows fans to cycle in sequence by sensing condensing pressures. Short cycling is normally causedby too close a differential in the control settings or set points. If flooding valves are used with fancycling, set valves to follow the fan cycling. Set pressure switches to at least 35 PSIG differentialsetting.

Any fan cycle that is less than three minutes is considered short cycling, and could bedetrimental to the system. Adjust controls accordingly. Wire the fan closest to the header end of thecondenser to run continuously, whenever the compressor(s) is (are) operational. Cycling all of thefans off will cause rapid, short cycling of the fans and erratic head pressure control.

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If additional head pressure control is necessary beyond letting the lead fan run, use variablespeed or flooding controls. If cycling the header fan is necessary for adequate head pressure control,cycle on pressure. Fans must not cycle in multiples except on double wide single circuit condenserswhere they may cycle in pairs (one motor on each side). Do not cycle more than two fans at a timeon double wide condensers and only one fan at a time on single wide condensers.

Fan Cycling Head Pressure ControlsCondenser fans are cycled to maintain adequate head pressure. Pressure fan cycling is available asoptional equipment.

Table 3, Factory Pressure Settings

Pressure fan cycling cycles fans in response to condenser pressure. This style of control is moreappropriate where the load on the condenser will vary due to multiple compressor operation orstages of unloading or systems incorporating heat reclaim or hot gas defrost. Fan pressure anddifferential settings may require adjustment to obtain stable operation.

SpeedTrolCondenser head pressure control is provided by varying the air flow through the condenser bychanging the RPM of the condenser fan. This control package is offered in combination withambient fan cycling. The fan motor next to the header end of the condenser is the variable speedfan. The remainder of the fans are constant speed and are cycled separately using pressure controls.On condensers with two rows of fans, two variable speed fans are provided (one per unit) and theremainder of the fans are constant speed.

Maintenance

Air-cooled condensing units require a minimum of maintenance. The unit coil will require aperiodic cleaning. Clean the unit using a brush, vacuum cleaner, pressurized air stream or acommercially available coil cleaning foam. All of the condenser fan motors have sealed ballbearings and do not need maintenance. If bearings fail, then replace bearings.

Cleaning InstructionsCAUTION

Never clean this unit with an acid-based cleaner.

Clean the finned surface at least every six months; more frequent cleaning may be required ifextreme conditions cause clogging or fouling of air passages through the finned surface.

Use Calgon Corporation's CalClean 41352 (or equal). Apply CalClean liberally to entering airand leaving air surfaces of the finned area according to label directions and rinse thoroughly toremove all cleaners..

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IOM ACAQ Air-Cooled Condensers 19

Notes

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Post Office Box 2510 Staunton, Virginia 24402-2510, USA, 540.248.0711


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