McQuay AGR 070AS - User Manual

Questions and Answers

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Dennis BaileyAug 15, 2025
What to do if the McQuay AGR 070AS Chiller compressor will not run?
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  mdavidAug 15, 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.
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Jamie MarshallAug 18, 2025
Why is the discharge pressure high in my McQuay Chiller?
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  Ernest BensonAug 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.
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Daniel GrantAug 21, 2025
What to do if McQuay AGR 070AS Chiller compressor overloads or circuit breakers open?
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  scottkristyAug 21, 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.
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xmooreAug 25, 2025
Why is the suction pressure low in my McQuay AGR 070AS?
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  Tina HancockAug 25, 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).
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Brian ClarkeAug 27, 2025
What causes low discharge pressure in a McQuay Chiller?
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  Sarah StantonAug 27, 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).
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Paul KnightAug 30, 2025
What causes high suction pressure in a McQuay AGR 070AS Chiller?
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  Lisa LeonAug 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.
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Steve MooreSep 2, 2025
Why does the freeze protection trip on my McQuay AGR 070AS Chiller?
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  Matthew EvansSep 2, 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.
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natashasnyderSep 5, 2025
What causes erratic loading and unloading in a McQuay AGR 070AS?
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  Jonathan PageSep 5, 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.
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Lisa TurnerSep 8, 2025
What causes compressor oil loss in my McQuay AGR 070AS?
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  Bryan LopezSep 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).
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Scott BerrySep 12, 2025
What causes the compressor internal motor switch to open in a McQuay AGR 070AS?
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  John FowlerSep 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).