K90-KPCS-IM-2
18/04/22
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System Troubleshooting Guide Continued
Condensing Unit Problem
Possible Causes
Discharge pressure too high.
1. Non-condensables in the system.
2. System overcharged with refrigerant.
3. Discharge service valve partially closed.
4. Condenser fan not running.
5. Dirty condenser coil.(air-cooled condensers)
6. Dirty tubes. .(water-cooled condensers)
7. Defective or improperly set water regulating valve.
(water-cooled condensers)
8. Defective or improperly set flooded head pressure control.
Discharge pressure too low.
1. Low suction pressure.
2. Cold ambient air.
3. Suction service valve partially closed.
4. Shortage of refrigerant.
5. Defective or improperly set water regulating valve.
(water-cooled condensers)
6. Defective or improperly set flooded head pressure control.
Suction pressure too high.
1. Excessive load.
2. Compressor internal valves broken.
3. Incorrect unit selection (undersized).
4. Improper TXV bulb charge.
Suction pressure too low.
1. Shortage of refrigerant.
2. Evaporator dirty or iced up.
3. Clogged liquid line filter drier.
4. Clogged suction line filter or compressor suction strainers.
5. Expansion valve malfunctioning.
6. Condensing temperature too low.
7. Improper TX valve selection.
8. Evaporator distributor feed problems.
Low or no oil pressure.
1. Low oil level. (trapped oil in evaporator or suction line)
2. Clogged suction oil strainer.
3. Excessive liquid refrigerant in the crankcase.
4. Worn oil pump.
5. Oil pump reversing gear sticking in the wrong position.
6. Worn bearings.
7. Loose fitting on oil line.
8. Pump housing gasket leaking.
Compressor loses oil.
1. Refrigerant leak.
2. Short cycling.
3. Excessive compressor ring blowby.
4. Refrigerant flood back.
5. Improper piping or traps.
6. Trapped oil in evaporator.
Compressor runs continuously
1. Excessive load.
2. Too low of a system thermostat setting or defective thermostat.
3. Shortage of refrigerant.
4. Leaking compressor internal valves.
5. Malfunctioning liquid line solenoid.
6. Incorrect unit selection (undersized).
SYSTEM TROUBLESHOOTING (cont’d)
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