McQuay ACZ 020A

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Installation, Operation and Maintenance Manual

IOMM ACZ1

Group:

Chiller

Part Number

: 330262002

Effective:

December 2001

Supersedes:

New

Air-Cooled Scroll Condensing Units

ACZ 010A – ACZ 039A

10 to 43 Tons, 35 to 150 kW

R-22, 60 Hertz

Table of Contents

Questions and Answers:

M
melissa11Aug 17, 2025
What to do if the McQuay Heat Pump compressor will not run?
- J
  Jose FullerAug 17, 2025
  If the McQuay Heat Pump compressor will not run, first ensure the main switch is closed. Check for blown fuses or open breakers, inspecting electrical circuits and motor windings for shorts, overloads, and loose connections; replace the fuse or reset the breaker if necessary. Also, check if thermal overloads have tripped (they auto reset). Inspect the contactor or coil for defects and repair or replace if needed. Determine if a protection device has shut the system off and correct the cause. If no cooling is required, the compressor should start on a call for cooling. Check if the liquid line solenoid will not open and repair or replace the coil if needed. Inspect the motor for open or short circuits, or burnout. Finally, check all wire junctions and tighten all terminals.
M
mario14Aug 19, 2025
What to do if my McQuay ACZ 020A has high discharge pressure?
- A
  Angie NixonAug 19, 2025
  If your McQuay Heat Pump has high discharge pressure, it could be due to several reasons. First, there might be noncondensables in the system, which should be removed using authorized procedures. Another cause could be a refrigerant overcharge, so remove the excess. Check if the fan is running and inspect the electrical circuit. Dirty condenser coils can also cause this issue, so clean the coil. Lastly, the FanTrol might be out of adjustment, so adjust the FanTrol setting.
J
Jennifer YangAug 22, 2025
Why is my McQuay Heat Pump compressor noisy or vibrating?
- J
  Joseph SuarezAug 22, 2025
  If your McQuay Heat Pump compressor is noisy or vibrating, it may be due to refrigerant flooding the compressor, so check the expansion valve setting. Another cause could be improper line support, in which case you should relocate or add supports. Finally, the compressor might be worn, requiring replacement.
A
Abigail JonesAug 25, 2025
What causes motor overload relays to open or blown fuses in McQuay ACZ 020A?
- R
  Rebecca WalshAug 26, 2025
  Motor overload relays opening or blown fuses in your McQuay Heat Pump can be caused by several factors. These include: 1. Low voltage during high loads, in which case you should check the supply voltage. 2. Defective or grounded motor wiring, requiring you to replace the compressor. 3. Loose power wiring, so check all connections and tighten them. 4. High condensing temperature (see steps for high discharge pressure). 5. Unbalanced voltage, so check the voltage and contact the power company.
M
Mr. Brandon ColemanAug 28, 2025
What to do if my McQuay ACZ 020A has low suction pressure?
- A
  Andrew GutierrezAug 28, 2025
  If your McQuay Heat Pump has low suction pressure, it could be due to a lack of refrigerant, so check for leaks and repair and replace the refrigerant. Another cause could be a dirty evaporator, which needs to be cleaned chemically. A clogged filter-drier can also cause this, so replace it. Additionally, the expansion valve might be malfunctioning; check and adjust for proper superheat. Low condensing temperature can also be a factor; check discharge pressure control settings.
J
Jeremy EvansAug 30, 2025
Why is my McQuay ACZ 020A Heat Pump's compressor losing oil?
- Z
  zfarrellAug 31, 2025
  If your McQuay Heat Pump's compressor is losing oil, it could be due to a lack of refrigerant, so check for leaks and repair them. Another cause could be suction superheat being too high, so adjust the superheat. Lastly, the crankcase heater might be burned out, requiring replacement.
X
xblevinsSep 2, 2025
What causes low discharge pressure in a McQuay Heat Pump?
- P
  pthompsonSep 2, 2025
  Low discharge pressure in a McQuay Heat Pump can be caused by a faulty condenser control, so check the condenser control operation. It can also be caused by a low refrigerant charge, so check for leaks and add refrigerant. Another possible cause is low suction pressure; see the low suction pressure steps.
K
Kaitlyn McdanielSep 5, 2025
What causes high suction pressure in a McQuay ACZ 020A?
- K
  Kyle BrownSep 5, 2025
  High suction pressure in a McQuay Heat Pump can be caused by an excessive load, so reduce the load or add capacity. It may also be caused by the expansion valve overfeeding, so check the remote bulb and regulate superheat.
L
Lindsay Mclean DDSSep 8, 2025
What causes a McQuay Heat Pump unit to not load or unload?
- S
  shafferashleySep 8, 2025
  If a McQuay Heat Pump unit will not load or unload, it could be due to a faulty controller sensor or a broken wire, requiring replacement. Another cause could be stages not set for the application, so adjust the thermostat setting.
T
Troy BrownSep 12, 2025
Why does my McQuay ACZ 020A Heat Pump have a short load/unload interval?
- E
  erica47Sep 12, 2025
  If your McQuay Heat Pump has a load/unload interval that is too short, it could be due to an erratic thermostat, in which case you should replace it. Another cause could be insufficient water flow, so adjust the flow.

McQuay ACZ 020A Specifications

General

Brand	McQuay
Model	ACZ 020A
Category	Heat Pump
Language	English

Summary

Introduction and Installation

Vibration Isolators

Recommendations and part numbers for vibration isolation during installation.

System Components and Piping

Refrigerant Piping Introduction

Importance and concerns related to proper refrigerant piping design.

Suction Lines

Guidelines for sizing and routing suction refrigerant lines for oil return.

Liquid Lines

Electrical and Physical Data

Electrical Data Overview

Field Wiring

Instructions and tables for field power wiring connections.

Wiring Diagram

Typical field wiring diagram illustrating power and control connections.

MicroTech II Controller Operation

Start-up and Shutdown Procedures

Setpoints and Alarms

Details on configurable setpoints and equipment protection alarms.

Using the Controller

Service and Troubleshooting

Thermostatic Expansion Valve

Optional Controls

Troubleshooting Chart

Common problems, their causes, and corrective actions.

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