McQuay AGR 055AS - User Manual

McQuay AGR 055AS

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Installation, Operation and Maintenance Manual

IOMM AGR

Group: Chiller

Part Number: 074641101

Effective: June 1998

Supersedes: IOM 690

690None

© 1997 McQuay International

Air-Cooled Reciprocating Chiller

AGR 055AS through 100AS

60 Hertz, English and Metric

Global Chiller Line

Table of Contents

Questions and Answers

A
Alyssa DoyleAug 16, 2025
What to do if the McQuay Chiller compressor will not run?
- T
  Terry HollowayAug 16, 2025
  If the McQuay Chiller's compressor won't run, several issues could be the cause. First, check if the main switch or circuit breakers are open and close the switch. Also, check for blown fuses, shorts, or grounds in the electrical circuits and motor windings. If thermal overloads have tripped, give the unit a close inspection when restarting. Other potential causes include a defective contactor or coil (repair or replace), system shutdown by safety devices (determine the cause and correct it before resetting), a liquid line solenoid that won't open (repair or replace), motor electrical trouble (check for opens, shorts, or burnout), or loose wiring (check and tighten all wire junctions). If no cooling is required, wait for the load.
J
Joe HarrisAug 19, 2025
Why is the discharge pressure high in my McQuay AGR 055AS Chiller?
- K
  Kimberly ArmstrongAug 19, 2025
  High discharge pressure in your McQuay Chiller can stem from several causes. Start by cleaning dirty condenser coils. Ensure the fan is operating correctly by checking the fan motor, contactor, contactor coil, and fan pressure switch, repairing or replacing any defective parts. Verify ambient conditions against design specifications. If the return water temperature is too high, try disabling a compressor on each. An overcharge of refrigerant or the presence of non-condensables can also cause this issue; remove the excess charge or non-condensables accordingly. Lastly, check if the discharge valve is partially closed and back seat the valve.
L
Lindsay CoxAug 22, 2025
What to do if McQuay AGR 055AS compressor overloads or circuit breakers open?
- K
  Keith JacksonAug 22, 2025
  If your McQuay Chiller experiences compressor overloads or open circuit breakers, several factors could be at play. Begin by checking the incoming line voltage and report any issues to your electrical supplier. High compressor amps could be the cause, so determine the underlying reason and correct it. Ensure all power wiring connections are tight. High condenser pressures could also trigger this issue; refer to the troubleshooting steps for high condenser pressure. Finally, check for single phasing and replace fuses or breakers as needed.
J
Jeremy ElliottAug 26, 2025
Why is the suction pressure low in my McQuay Chiller?
- T
  trobinsonAug 26, 2025
  Low suction pressure in your McQuay Chiller can be caused by several factors: * A low refrigerant charge (add refrigerant). * A defective expansion valve (check operation, repair or replace). * A dirty filter drier (replace cores). * Reduced water flow (increase water to design GPM). * A hot gas bypass valve not set properly (set valve for a higher pressure). * A liquid line solenoid valve not opening (repair or replace). * A defective UNT controller (check water sensor, set point dial, control band dial; calibrate, repair, or replace). * Gasket failure in evap head ring (replace gasket).
D
Dylan LoweryAug 28, 2025
What causes low discharge pressure in a McQuay Chiller?
- S
  Sonya OliverAug 28, 2025
  Low discharge pressure in a McQuay Chiller can occur due to several reasons. The fan contactor might have failed in the closed position, requiring repair or replacement. A defective fan pressure switch should be replaced. Low ambient temperatures can also cause this; consider installing a SpeedTrol Kit. Other potential causes include a low refrigerant charge (add refrigerant), reduced chilled water flow (check flow and correct), or the system operating on hot gas bypass with no load (adjust hot gas bypass to maintain a higher evaporator pressure).
T
Tiffany RobertsAug 31, 2025
What causes high suction pressure in a McQuay AGR 055AS Chiller?
- J
  jessica40Aug 31, 2025
  High suction pressure in a McQuay Chiller can be attributed to a few key issues. An excessive load, indicated by high return water temperature, can be a cause; check water flow and reduce the load. The controller might not be staging up correctly, so check the UNT controller and replace it if defective. Reduced compressor capacity could also be the culprit, necessitating compressor replacement. High condenser pressure can also be associated with this issue; investigate the causes of high condenser pressure.
D
David RiveraSep 3, 2025
Why does the freeze protection trip on my McQuay AGR 055AS?
- L
  Lisa AndersenSep 3, 2025
  Freeze protection trips in your McQuay Chiller can be triggered by several issues. Defective pressure transducers may be the cause; compare their output to actual refrigerant pressures. Check for low water flow (correct water GPM) or low/erratic water flow (check pump operation, water strainer, and air handler control valves). The controller stage timing might be off (check and reset as necessary). A defective TXV (check, repair, or replace), an improperly set hot gas bypass (set the hot gas bypass), or low ambient operation (install SpeedTrol, wind baffles) can also cause freeze protection trips.
C
Carla SmithSep 6, 2025
What causes erratic loading and unloading in a McQuay Chiller?
- A
  Andrew KirkSep 6, 2025
  Erratic loading and unloading in your McQuay Chiller can stem from several causes. The chilled water flow might be erratic; check for the reasons and correct them. An erratic system load could also be the issue; check the water flow control valve operation. A bad water sensor should be replaced. The reset function calibration may be off and needs recalibration. Lastly, a defective UNT controller should be replaced.
J
Jodi AndrewsSep 9, 2025
What causes compressor oil loss in my McQuay AGR 055AS Chiller?
- J
  Jacob BrownSep 9, 2025
  Compressor oil loss in your McQuay Chiller can be due to excessive refrigerant flood back (check TXV, repair or replace), a defective crankcase heater (replace heater), a low refrigerant charge (add refrigerant), or an improperly set hot gas bypass (increase hot gas flow).
J
julie20Sep 12, 2025
What causes the compressor internal motor switch to open in a McQuay AGR 055AS?
- I
  ibarrettSep 12, 2025
  If the compressor internal motor switch opens in your McQuay Chiller, it could be due to high compressor amps (refer to troubleshooting for high compressor amps) or a damaged motor winding (check motor winding resistance; replace if defective).

McQuay AGR 055AS Specifications

General

Brand	McQuay
Model	AGR 055AS
Category	Chiller
Language	English

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