Troubleshooting - Refrigeration Circuit - Greenheck DGX Installation, Operation And Maintenance Manual

Troubleshooting – Refrigeration Circuit
Symptom
Compressor starts
but cuts out on high
pressure switch.
High pressure
activates at 600 psig
Compressor cuts out
on thermal overload
Compressor hums,
but will not start
Compressor noisy or
vibrating
Always have a completed Pre Start-Up Checklist, Unit Start-Up Checklist and Optional Accessories Checklist
prior to requesting parts or service information.
14
Packaged DX Module for Make-Up Air Unit
Possible Cause
Refrigerant overcharge.
Condenser fan motor defective.
Condenser coil inlet obstructed or dirty.
Air or non-condensables in system.
Defective high pressure switch.
Restriction in discharge or liquid line.
Condensing fan relay not pulling in.
Reheat valve and bypass valve not
opening.
Low voltage.
Sustained high discharge pressure.
High suction and discharge pressures.
Defective compressor overload.
Improper refrigerant charge.
Improperly wired.
Loose wiring.
Defective start relay.
Motor windings damaged.
Improperly wired.
Low line voltage.
Loose wiring.
Defective start relay.
Motor winding damaged.
Internal compressor mechanical damage.
Refrigerant overcharge.
Liquid floodback.
Tubing rattle.
Scroll Compressor rotating in reverse
(3-phase).
Worn or damaged compressor.
Improper mounting on unit base.
(continued)
Corrective Action
Check pressures, charge by subcooling.
Check fan motor.
Check coil and inlet clearances.
Check high side equalized pressures,
check thermal expansion valves.
Replace.
Check refrigerant line pressures, check
thermal expansion valves, replace any
defective component.
Replace.
Check valves or valve circuit board.
Check voltage.
Check running amperage and conditions
described under "low suction pressure"
symptoms.
Check thermal expansion valve setting,
check for air in system. Check air
conditions and cfm.
If compressor is hot, allow compressor
to cool for two hours. Recheck for open
circuit.
Check subcooling.
Review wiring schematics.
Check all connections.
Replace relay.
Verify amp draw.
Review wiring schematics.
Check voltage.
Check all connections.
Replace relay.
Verify amp draws. Replace compressor if
necessary.
Replace.
Check pressures and subcooling.
Check thermal expansion valve setting.
Check for refrigerant overcharge.
Dampen tubing vibration by taping or
clamping. Carefully bend tubing away from
contact where possible.
Rewire for opposite rotation.
Replace the compressor.
Check that compressor is properly
isolated.
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