McQuay SEASONCON ALP-120C User Manual

59 pages

Questions and Answers:

R
Robert HortonAug 19, 2025
Why McQuay Heat Pump compressor will not run?
- E
  Edward JamesSep 12, 2025
  The compressor might not be running due to several reasons. The main switch could be open (close it), a fuse could be blown (replace the fuse or reset breakers after correcting the fault), or circuit breakers could be open (check electrical circuits and motor winding for shorts or grounds). Thermal overloads might have tripped (check the unit closely when it comes back online), the contactor or coil could be defective (repair or replace it), or the system might have been shut down by safety devices (determine the type and cause of shutdown and correct it before resetting the safety switch).
K
Kimberly MoonAug 21, 2025
What to do if my McQuay Heat Pump has low suction pressure?
- K
  Kimberly SummersAug 21, 2025
  Low suction pressure may be due to several factors. There could be a lack of refrigerant (check for leaks, repair, and add charge), a dirty evaporator (clean it chemically), or a clogged liquid line filter-drier (replace it). Additionally, the suction line or compressor suction gas could be clogged (clean strainers), the expansion valve might be malfunctioning (check and reset for proper superheat), or the condensing temperature may be too low (check the means for regulating condensing temperature).
C
christophersmithAug 23, 2025
How to fix high discharge pressure in McQuay Heat Pump?
- J
  Justin LittleAug 23, 2025
  High discharge pressure can occur due to several reasons: there may be noncondensables in the system (purge them), the system might be overcharged with refrigerant (remove the excess), the discharge shutoff valve could be partially closed (open the valve), or the fan might not be running (check the electrical circuit).
S
sara39Aug 27, 2025
Why my McQuay Heat Pump compressor loses oil?
- C
  Chelsea ArnoldAug 28, 2025
  The compressor may lose oil due to a lack of refrigerant (check for leaks and repair; add refrigerant), excessive compression ring blow-by (replace the compressor), suction superheat being too high (adjust superheat), or a burned-out crankcase heater (replace the crankcase heater). Other causes may include insufficient oil in the system (add oil until the sight glass is 1/3 full), suction risers that are too large (check line sizing at design conditions and change if incorrect), or insufficient traps in suction risers (install suction P-traps at each 20-foot vertical rise).
D
djamesAug 30, 2025
How to reduce noise of vibrating McQuay Heat Pump compressor?
- A
  Autumn LynnAug 30, 2025
  A noisy or vibrating compressor may be caused by flooding of refrigerant into the crankcase (check the setting of the expansion valve) or improper piping support on the suction or liquid line (relocate, add, or remove hangers).
W
Walter HicksSep 1, 2025
What causes low discharge pressure in McQuay Heat Pump?
- T
  Timothy RomeroSep 1, 2025
  Low discharge pressure can be attributed to a dirty condenser coil (clean the coil) or a FANTROL out of adjustment (adjust FANTROL settings).
J
Jacob MooreSep 3, 2025
What to do if McQuay Heat Pump has high suction pressure?
- B
  Benjamin PriceSep 3, 2025
  High suction pressure can be caused by an excessive load (reduce the load or add additional equipment) or an expansion valve overfeeding (check the remote bulb and regulate superheat).
K
kruizSep 5, 2025
Why McQuay Heat Pump compressor thermal protector switch open?
- M
  Melanie DavisSep 5, 2025
  The compressor thermal protector switch might be open due to operating beyond design conditions (add facilities so conditions are within allowable limits), a discharge valve being partially shut (open the valve), or a blown valve plate gasket (replace the gasket).
J
Jamie MasonSep 7, 2025
What causes McQuay Heat Pump compressor not to unload or load?
- B
  Bryan HensleySep 7, 2025
  The compressor's failure to unload or load may be due to a defective capacity control (replace it), a defective unloader mechanism (replace it), or a faulty thermostat stage or broken capillary tube (replace it). Also, ensure that the thermostat setting is appropriate for the application by resetting it.
C
Carla BlackSep 9, 2025
What to do if liquid line solenoid will not open in McQuay Heat Pump?
- D
  Darrell DavilaSep 10, 2025
  Repair or replace the coil.

McQuay SEASONCON ALP-120C Specifications

General

Category	Heat Pump
Model	SEASONCON ALP-120C
Cooling Capacity	12.0 kW
Heating Capacity	13.5 kW
Refrigerant	R410A
Operating Temperature Range (Heating)	-15°C to 24°C

Summary

Field Wiring

General Wiring Guidelines

Typical Field Wiring Diagrams

Visual guides for unit wiring, including controls and power.

Wire Sizing Ampacities

Normal Sequence of Operation

Startup

Initial steps for starting the unit and its components.

Pumpdown

Typical Control and Safeties Wiring Diagrams

Typical Thermostat Wiring Diagrams

4-Stage Thermostat

6-Stage Thermostat

8-Stage Thermostat

Drawing Reference Decision Table

Power Schematics for Compressor and Condenser Fan Motors

Table to find specific power schematic drawings based on unit configuration.

Control and Safety Schematics

Table to find specific control and safety schematic drawings.

Thermostat Control Schematic

Table to find specific thermostat control schematic drawings.

Startup and Shutdown

Pre-Startup

Checks before initial unit startup.

Initial Startup

Steps for starting the unit for the first time.

Temporary Shutdown

Extended Shutdown

System Maintenance

General

Compressor Oil Level

Procedures for checking and adding oil to compressors.

Refrigerant Sightglass

Appendix

Standard Controls

Oil Pressure Safety Control

Description and check of the oil pressure safety control.

High Pressure Control

Low Pressure Control

FANTROL Head Pressure Control

Compressor Lockout

Optional Controls

SPEEDTROL Head Pressure Control (Optional)

Description of the optional SPEEDTROL system for head pressure.

Compressor Unloaders (Optional)

Low Ambient Start (Optional)

High Ambient (Optional)

Part Winding Start (Optional)

Phase/Voltage Monitor (Optional)

Hot Gas Bypass (Optional)

ALP Controls, Settings, and Functions

Troubleshooting Chart

Compressor Will Not Run

Troubleshooting steps for a non-running compressor.

Compressor Noisy or Vibrating

Troubleshooting steps for noise or vibration issues.

High Discharge Pressure

Troubleshooting steps for high discharge pressure.

Low Discharge Pressure

Troubleshooting steps for low discharge pressure.

High Suction Pressure

Troubleshooting steps for high suction pressure.

Low Suction Pressure

Troubleshooting steps for low suction pressure.

Compressor Will Not Unload or Load

Troubleshooting for compressor loading/unloading issues.

Compressor Loading/Unloading Intervals Too Short

Troubleshooting for compressor short cycling.

Loss of Oil Pressure or Nuisance Oil Pressure Control Trips

Troubleshooting for oil pressure related trips.

Compressor Loses Oil

Troubleshooting steps for compressor oil loss.

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