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McQuay AGZ 065A - User Manual

McQuay AGZ 065A
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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

Other manuals for McQuay AGZ 065A

Preview: Installation And Operation Manual
Installation And Operation Manual88 pages

Questions and Answers

  • J
    James DavisAug 22, 2025
    What causes high discharge pressure in a McQuay AGZ 065A Chiller and how to fix it?
    • J
      Jamie GrayAug 22, 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).
  • D
    Darrell ClarkAug 25, 2025
    What to do if my McQuay AGZ 065A has compressor overloads or circuit breakers open?
    • M
      markortegaAug 25, 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).
  • J
    Jerry MartinezAug 27, 2025
    What causes low suction pressure in McQuay AGZ 065A?
    • L
      loribrownAug 27, 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).
  • T
    Taylor HaleAug 28, 2025
    Why is the discharge pressure low in my McQuay AGZ 065A?
    • K
      Kristen EvansAug 28, 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).
  • C
    Chris ChristensenAug 29, 2025
    What causes high suction pressure in a McQuay AGZ 065A?
    • M
      Margaret SanchezAug 29, 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
    Susan JacksonAug 31, 2025
    What causes a McQuay AGZ 065A to have erratic loading and unloading?
    • R
      robertrobertsonAug 31, 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).
  • V
    vsimpsonSep 2, 2025
    How to resolve freeze protection trips in a McQuay AGZ 065A?
    • K
      Kevin HortonSep 2, 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).
  • J
    Jeffrey DanielSep 4, 2025
    What to do if my McQuay AGZ 065A Chiller has compressor internal motor switch open?
    • M
      Michael WilkinsonSep 4, 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).
  • T
    Tiffany HoffmanSep 5, 2025
    What causes compressor oil loss in a McQuay Chiller?
    • C
      Christine PhillipsSep 6, 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).
  • K
    Kara BowmanSep 9, 2025
    What to do if a McQuay AGZ 065A has high discharge pressure?
    • J
      jamiedaltonSep 9, 2025
      To address high discharge pressure in your McQuay Chiller, begin by purging any noncondensables from the system. If there's excess refrigerant, remove it and check the liquid subcooling. Ensure the valve is open. Inspect the FanTrol wiring and check both the electrical circuit and fan motor. Finally, clean the coil to ensure proper heat exchange.

Summary

Introduction

General Description

Overview of the chiller's components, features, and electrical system.

Inspection

Procedures for checking the unit upon arrival for damage and verifying nameplate data.

Installation

Handling and Location

Guidance on safe unit movement, placement, and foundation requirements.

Clearances and Sound Isolation

Requirements for airflow, service access, and noise reduction measures.

Vibration Isolators

Details on selecting and installing vibration isolators for roof-mounted units.

Physical Data

Electrical Data

Field Wiring

Guidelines for connecting power, field wiring requirements, and wire sizing.

Electrical Legend

Explanation of symbols and abbreviations used in electrical diagrams.

Dimensional Data

Startup

Pre Start-Checkout

Essential checks before applying power and starting the controller.

Start-Up Procedures

Step-by-step guide for initial unit startup and operation.

Shutdown Procedures

Instructions for temporary and extended unit shutdowns.

Operation

Sequence of Operation

Detailed explanation of how the chiller starts, stages, and operates.

System Checks and Adjustments

Covers filter driers, sightglasses, charging, TXV, and heaters.

Water Cooler

Information on the evaporator's water cooler unit and connections.

Global UNT Controller Installation and Operation

General Description

Overview of the microprocessor-based leaving water controller and its functions.

Controller Inputs;Outputs

Details on analog and digital inputs, outputs, and their connections.

UNT Troubleshooting Chart

Guide to diagnosing and resolving common problems with the UNT controller.

MicroTech Controller Installation and Operation

General Description

Overview of the MicroTech control panel and its capabilities.

Controller Inputs;Outputs

Information on analog/digital inputs, outputs, and relay board functions.

Test Procedures

Methods for diagnosing and troubleshooting MicroTech controller hardware issues.

Manual Operation

Compressor Staging

Explanation of how compressors stage and control head pressure.

Pumpdown Control

Description of the unit's one-time pumpdown sequence and conditions.

Sequence of Operation

Off Conditions

Conditions that prevent the chiller from starting or cause it to turn off.

Start - Up

Detailed steps for initiating chiller operation and staging.

Low Ambient Start

Specific logic for starting the chiller in low ambient temperature conditions.

Start-Up and Shutdown

Pre-Start Checkout

Essential checks before applying power and starting the controller.

Extended Shutdown

Procedures for safely shutting down the unit for extended periods.

Unit Maintenance

General Maintenance

Routine checks, compressor maintenance, lubrication, and electrical terminal inspection.

Preventive Maintenance Schedule

A schedule outlining weekly, monthly, and annual maintenance tasks.

Service

Filter-Driers

Information on filter-drier replacement based on pressure drop or moisture indication.

Refrigerant Charging

Procedures for field charging refrigerant and checking system subcooling.

AGZ Troubleshooting Chart

McQuay AGZ 065A Specifications

General IconGeneral
ModelAGZ 065A
ManufacturerMcQuay
CategoryChiller
Cooling Capacity65 tons
RefrigerantR-410A
Compressor TypeScroll
Number of Compressors2
Voltage460V/3Ph/60Hz

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