Carrier 50GCQ Series - User Manual

Carrier 50GCQ Series

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Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.

Catalog No. 04-53500340-01 Printed in U.S.A. Form 50GCQ-4-6-02SM Pg 1 8-23 Replaces: 50GCQ-4-6-01SM

Service and Maintenance Instructions

CONTENTS

Page

SAFETY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . 2

UNIT ARRANGEMENT AND ACCESS . . . . . . . . . . . . 3

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Routine Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 3

Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

SUPPLY FAN (BLOWER) SECTION . . . . . . . . . . . . . . 4

Supply Fan (Direct-Drive) . . . . . . . . . . . . . . . . . . . . . . 4

Staged Air Volume . . . . . . . . . . . . . . . . . . . . . . . . . . 10

COOLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Condenser Coil (Outdoor) . . . . . . . . . . . . . . . . . . . . 10

Evaporator Coil (Indoor) . . . . . . . . . . . . . . . . . . . . . . 10

Condenser Coil Maintenance and Cleaning 

Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . 10

Evaporator Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Refrigeration System Components . . . . . . . . . . . . . 12

Evaporator Coil Metering Devices . . . . . . . . . . . . . . 12

THERMOSTATIC EXPANSION VALVE (TXV) . . . . . 13

TXV Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Replacing TXV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Refrigerant System Pressure Access Ports . . . . . . 14

PURON (R-410A) REFRIGERANT . . . . . . . . . . . . . . . 15

Refrigerant Charge . . . . . . . . . . . . . . . . . . . . . . . . . . 15

COOLING CHARGING CHARTS . . . . . . . . . . . . . . . . 15

COMPRESSOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Replacing Compressor . . . . . . . . . . . . . . . . . . . . . . . 16

Compressor Rotation . . . . . . . . . . . . . . . . . . . . . . . . 16

Filter Drier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Condenser-Fan Adjustment . . . . . . . . . . . . . . . . . . . 17

Troubleshooting Cooling System . . . . . . . . . . . . . . 18

CONVENIENCE OUTLETS . . . . . . . . . . . . . . . . . . . . 19

Convenience Outlets . . . . . . . . . . . . . . . . . . . . . . . . 19

Installing Weatherproof Cover . . . . . . . . . . . . . . . . . 19

Non-Powered Type . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Unit-Powered Type . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Duty Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Fuse on Powered Type . . . . . . . . . . . . . . . . . . . . . . . 20

COMMERICAL DEFROST CONTROL . . . . . . . . . . . . 20

Reversing Valve Control . . . . . . . . . . . . . . . . . . . . . 21

Compressor Control . . . . . . . . . . . . . . . . . . . . . . . . . 21

Auxiliary (Electric) Heat Control . . . . . . . . . . . . . . . 21

Defrost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

ELECTRIC HEATERS . . . . . . . . . . . . . . . . . . . . . . . . 22

Single Point Boxes and Supplementary Fuses . . . 23

Safety Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Completing Heater Installation . . . . . . . . . . . . . . . . .23

SMOKE DETECTORS . . . . . . . . . . . . . . . . . . . . . . . . .24

System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Smoke Detector Sensor . . . . . . . . . . . . . . . . . . . . . .24

Smoke Detector Locations . . . . . . . . . . . . . . . . . . . .24

Completing Installation of Return Air Smoke

Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

FIOP Smoke Detector Wiring and Response . . . . .26

SENSOR AND CONTROLLER TESTS . . . . . . . . . . .27

Sensor Alarm Test . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Controller Alarm Test . . . . . . . . . . . . . . . . . . . . . . . .27

Dirty Controller Test . . . . . . . . . . . . . . . . . . . . . . . . .27

Dirty Sensor Test . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Changing the Dirty Sensor Test . . . . . . . . . . . . . . . .27

Remote Station Test . . . . . . . . . . . . . . . . . . . . . . . . .27

SD-TRM4 Remote Alarm Test Procedure . . . . . . . .28

Remote Test/Reset Station Dirty Sensor Test . . . .28

Dirty Sensor Test Using an SD-TRM4 . . . . . . . . . . .28

Detector Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

PROTECTIVE DEVICES . . . . . . . . . . . . . . . . . . . . . . .30

Compressor Protection . . . . . . . . . . . . . . . . . . . . . . .30

Relief Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Control Circuit, 24-v . . . . . . . . . . . . . . . . . . . . . . . . . .30

SYSTEMVU CONTROL SYSTEM . . . . . . . . . . . . . . . .30

SystemVu Interface . . . . . . . . . . . . . . . . . . . . . . . . . .30

Additional SystemVu Installation and

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . .30

RTU OPEN CONTROL SYSTEM . . . . . . . . . . . . . . . .32

Sensory/Accessory Installation . . . . . . . . . . . . . . . .32

Additional RTU Open Installation and

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . .33

ECONOMIZER SYSTEMS . . . . . . . . . . . . . . . . . . . . .33

EconoMi$er 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

EconoMi$er IV (Field-Installed Accessory) . . . . . . .35

EconoMi$er X (Factory Option) . . . . . . . . . . . . . . . .42

PRE-START-UP/START-UP . . . . . . . . . . . . . . . . . . . .53

START-UP, GENERAL . . . . . . . . . . . . . . . . . . . . . . . .54

Unit Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54

Additional Installation/Inspection . . . . . . . . . . . . . .54

Return-Air Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . .54

Outdoor-Air Inlet Screens . . . . . . . . . . . . . . . . . . . . .54

Compressor Mounting . . . . . . . . . . . . . . . . . . . . . . .54

Internal Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54

Refrigerant Service Ports . . . . . . . . . . . . . . . . . . . . .54

Compressor Rotation . . . . . . . . . . . . . . . . . . . . . . . .54

Refrigerant Service Ports . . . . . . . . . . . . . . . . . . . . .54

50GCQ*04-06

Single Package Rooftop Heat Pump

with Puron

®

(R-410A) Refrigerant

3 to 5 Nominal Tons

Table of Contents

Questions and Answers:

J
Jonathan RobertsonAug 12, 2025
Why won't my Carrier Heat Pump compressor start, but the outdoor fan runs?
- A
  Anthony ThomasAug 13, 2025
  If the compressor in your Carrier Heat Pump won't start but the outdoor fan runs, several issues could be responsible. Check for faulty wiring or loose connections in the compressor circuit, and repair or replace as needed. The compressor motor might be burned out, seized, or have an open internal overload; determine the cause and replace the compressor, or allow enough time for the internal overload to cool and reset. A defective run/start capacitor, overload, or start relay could also be the problem; determine the cause and replace the compressor or allow time for the internal overload to cool and reset. Lastly, one leg of the 3-phase power might be dead; replace the fuse or reset the circuit breaker and determine the cause.
D
Donna WilliamsAug 19, 2025
Why does my Carrier Heat Pump compressor operate continuously?
- N
  nicholehernandezAug 19, 2025
  If the compressor on your Carrier Heat Pump is operating continuously, it could be due to several reasons. A dirty air filter can cause this issue, so replace the filter. The unit might also be undersized for the load, in which case you should decrease the load or increase the unit size. If the thermostat is set too low in cooling mode, reset it to a higher temperature. A low refrigerant charge or air in the system can also cause continuous operation; locate any leaks, repair them, and recharge the system, or recover the refrigerant, evacuate the system, and recharge it. Lastly, a dirty or restricted outdoor coil can be the problem; clean the coil or remove any restrictions.
T
Timothy SmallAug 27, 2025
What causes excessive head pressure in Carrier Heat Pump?
- E
  Elizabeth KellerAug 27, 2025
  Excessive head pressure in your Carrier Heat Pump can be caused by a few things. A dirty air filter can contribute to this, so replace it. If you're in cooling mode, a dirty outdoor coil can also be the culprit; clean the coil. An overcharge of refrigerant is another possibility; recover the excess refrigerant. Air in the system can also lead to high head pressure; in this case, recover the refrigerant, evacuate the system, and recharge it. Finally, restricted condensing air or air short-cycling can cause this issue; determine the cause and correct it.
J
Joanne GarciaSep 3, 2025
What causes low head pressure in Carrier 50GCQ?
- F
  Frank JonesSep 3, 2025
  Low head pressure in a Carrier Heat Pump can arise from a few causes. A low refrigerant charge is a primary suspect, so check for leaks, repair them, and recharge the system. Defective compressor scroll plates can also lead to this issue, requiring compressor replacement. Lastly, a restriction in the liquid tube might be the cause; remove the restriction to resolve the problem.
B
Brittany MooreSep 7, 2025
What could cause excessive suction pressure in Carrier Heat Pump?
- S
  stephaniejonesSep 7, 2025
  Excessive suction pressure in your Carrier Heat Pump can be attributed to several factors. A high heat load can cause this issue; check for the source and eliminate it. Defective compressor scroll plates can also lead to excessive suction pressure, requiring compressor replacement. Finally, refrigerant overcharge can be the culprit; recover the excess refrigerant to resolve the problem.
S
sanchezandrewNov 15, 2025
How to troubleshoot Carrier Heat Pump compressor and outdoor fan not starting?
- S
  Susan GrossNov 15, 2025
  If the compressor and outdoor fan of your Carrier Heat Pump won't start, several factors could be at play. First, there might be a power failure, in which case you should call the power company. A blown fuse or tripped circuit breaker could also be the culprit; replace the fuse or reset the breaker, and determine the root cause. Other potential issues include a defective thermostat, contactor, transformer, control relay, or capacitor, all of which would require component replacement. Insufficient line voltage or incorrect/faulty wiring can also prevent startup; determine the cause and correct it, or check the wiring diagram and rewire accordingly. Also, ensure the thermostat isn't set too high. Finally, a tripped high or low pressure switch, or a tripped freeze-up protection thermostat, co...

Carrier 50GCQ Series Specifications

General

Series	50GCQ
Type	Heat Pump
Refrigerant	R-410A
Voltage	208/230V
Cooling Capacity	24, 000 - 60, 000 BTU/h

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