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McQuay AGZ 035A - User Manual

McQuay AGZ 035A
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Installation, Operation and Maintenance Manual
IOMM AGZ-3
Group: Chiller
Part Number: 074641003
Effective: June 2002
Supercedes: IOMM AGZ-2
Air-Cooled Scroll Compressor Chiller
AGZ 035A through 065A
60 Hertz, R-22
Global Chiller Line

Table of Contents

Questions and Answers

  • P
    perezhannahAug 18, 2025
    What causes high discharge pressure in a McQuay Chiller and how to fix it?
    • S
      Sarah BeardAug 18, 2025
      High discharge pressure in your McQuay Chiller can stem from several issues: dirty condenser coils (clean them), a fan not operating (check the fan motor, contactor, contactor coil, and fan pressure switch, repairing or replacing any defective parts), high ambient conditions (check against design conditions), high return water temperature (disable a compressor on each), an overcharge of refrigerant (remove the excessive amount), non-condensables (remove them), or a discharge valve being partially closed (back seat valve).
  • K
    Kyle MasonAug 21, 2025
    What to do if my McQuay AGZ 035A Chiller has compressor overloads or circuit breakers open?
    • D
      Dana OsborneAug 22, 2025
      If your McQuay Chiller experiences compressor overloads or open circuit breakers, it could be due to low line voltage (check incoming voltage and report to the electrical supplier), high compressor amps (determine the cause and correct it), loose power wiring (tighten all connections), high condenser pressures (refer to High Condenser Pressure solutions), or single phasing (replace fuses or breaker).
  • D
    David HowardAug 25, 2025
    What causes low suction pressure in McQuay AGZ 035A Chiller?
    • S
      Shane MorganAug 25, 2025
      Low suction pressure in a McQuay Chiller can result from a low refrigerant charge (add refrigerant), a defective expansion valve (check operation and 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 the 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, and control band dial; calibrate, repair, or replace), or a gasket failure in the evaporator head ring (replace the gasket).
  • K
    Kurt EricksonAug 27, 2025
    Why is the discharge pressure low in my McQuay AGZ 035A Chiller?
    • L
      Lauren AndersonAug 27, 2025
      Low discharge pressure in your McQuay Chiller could be caused by a fan contactor failed in closed position (repair or replace), a defective fan pressure switch (replace the pressure switch), low ambient temperatures (install a SpeedTrol Kit), low refrigerant charge (add refrigerant), reduced chilled water flow (check flow and correct), or no load and on hot gas bypass (adjust hot gas bypass to maintain a higher evaporator pressure).
  • A
    Alexandria CohenAug 30, 2025
    What causes high suction pressure in a McQuay Chiller?
    • S
      shawnchambersAug 30, 2025
      High suction pressure in a McQuay Chiller can be caused by an excessive load (high return water temp) - check water flow, reduce load; a controller not staging up - check UNT controller, replace if defective; compressor capacity reduced - replace compressor; can be associated with high condenser pressure - check reasons for high condenser pressure.
  • S
    Stephen HillSep 3, 2025
    What causes a McQuay AGZ 035A to have erratic loading and unloading?
    • J
      John WalkerSep 3, 2025
      Erratic loading and unloading in a McQuay Chiller can stem from several causes: erratic chilled water flow (check for reasons and correct), erratic system load (check water flow control valve operation), a bad water sensor (replace it), reset function calibration issues (re-calibrate), or a defective UNT controller (replace it).
  • K
    katherinejohnsonSep 5, 2025
    How to resolve freeze protection trips in a McQuay AGZ 035A Chiller?
    • D
      Darren MartinezSep 5, 2025
      Freeze protection trips in your McQuay Chiller might be due to defective pressure transducers (compare output to actual refrigerant pressures), low water flow (check water GPM and correct), low loads or erratic water flow (check pump operation, water strainer, and air handler control valves), controller stage timing issues (check timing and reset as necessary), a defective TXV (check and repair or replace), the hot gas bypass not set properly (set hot gas bypass), or low ambient operation (install SpeedTrol, wind baffles).
  • D
    Dr. William FrySep 9, 2025
    What to do if my McQuay AGZ 035A Chiller has compressor internal motor switch open?
    • J
      Jessica ThomasSep 9, 2025
      If the compressor internal motor switch is open in your McQuay Chiller, it could be because the compressor amps are high (refer to the information concerning high compressor amps) or the motor winding is damaged (check motor winding resistance and replace if defective).
  • A
    Angelica BurtonSep 12, 2025
    What causes compressor oil loss in a McQuay AGZ 035A Chiller?
    • H
      Herbert FullerSep 12, 2025
      Compressor oil loss in a McQuay Chiller may 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 the hot gas bypass not set properly (increase hot gas flow).
  • D
    Dr. Jimmy GuzmanNov 15, 2025
    Why is my McQuay Chiller's compressor not running?
    • M
      Mrs. Charlene Woods DDSNov 15, 2025
      Several factors can prevent the compressor from running. It could be due to an open main switch or circuit breakers (close the switch), a blown fuse (check electrical circuits and motor winding for shorts or grounds; overloading is possible, so replace the fuse or reset breakers after fixing the fault), tripped thermal overloads or blown fuses (overloads are auto reset, so closely monitor the unit when it's operating again), a defective contactor or coil (repair or replace it), the system being shut down by protection devices (determine the type and cause of shutdown and correct it before resetting the control), no cooling being required (wait for the load), the liquid line solenoid not opening (repair or replace it), motor electrical trouble (check the motor for opens, shorts, or burnout)...

Summary

Introduction

General Description

Overview of the chiller unit's components and features.

Installation

Handling

Location

Guidelines for selecting a suitable installation site, considering foundation and clearances.

Clearances

Required space around the unit for proper airflow and service access.

Water Piping

Electrical Data

Field Wiring

Guidelines and requirements for connecting electrical power to the unit.

Global UNT Controller

Controller Inputs;Outputs

Alarms

Information on system and circuit alarm conditions and their meanings.

MicroTech Controller

Installation and Operation

Unit set points and calibration

Controller Inputs;Outputs

Operation

Startup

Procedures for safely starting the chiller unit.

Electrical Check Out

Sequence of Operation

Filter Driers

Troubleshooting

UNT Troubleshooting Chart

Common problems, causes, and corrective actions for the UNT controller.

MicroTech Controller Troubleshooting

Analysis of issues related to the MicroTech control board and its components.

Test Procedures

Unit Maintenance

Preventive Maintenance Schedule

A schedule outlining recommended maintenance tasks and frequencies.

Service

Filter-Driers

Refrigerant Charging

Procedures and guidelines for recharging the refrigerant system.

AGZ Troubleshooting Chart

McQuay AGZ 035A Specifications

General IconGeneral
BrandMcQuay
ModelAGZ 035A
CategoryChiller
LanguageEnglish

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