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Troubleshooting
60
Flooding
Defective or improperly set expansion
valve
Increase superheat or replace valve
Evaporator fan motor or belt Correct problem or replace fan motor and/
or belts.
Low condensing pressure Check head pressure control device
Slipping belts Inspect and adjust
Low compressor capacity or
inability to pull down system
Compressor rotation in reverse
direction.
Check for proper power phase wiring to
unit and to compressor motor.
Leaking liquid line solenoid valve or dirt
in valve
Replace valve if clean; clean out valve if
dirty.
Compressor noisy Loose compressor or piping support Tighten clamps.
Pipe rattle Loose pipe connections Check pipe connections
Compressor running hot
Compression ratio too high Check setting of high and low pressure
switches. Check condenser -- is it
plugged? Check that all evaporator and
condenser fans are operating properly.
Compressor cycles intermittently
Low-pressure switch erratic in operation Check tubing to switch to see if clogged or
crimped. Check for proper switch
operation.
Insufficient refrigerant in system Check for leaks, fix, and add refrigerant on
air cooled unit. Evacuate and recharge
water/glycol unit.
Suction service valve closed Open valve.
Insufficient fluid flowing through
condenser or clogged condenser, or
dirty air cooled condenser coils
Adjust fluid regulating valve to condenser.
Flush the condenser.
Discharge service valve not fully open Open valve
Compressor cycles continually
Faulty low pressure switch Repair or replace.
Dirt or restriction in tubing to pressure
stat
Check and clean tubing.
Defective liquid line solenoid valve Check valve and solenoid operator;
replace if necessary.
Plugged filter-drier Replace filter.
Compressor motor protectors
tripping or cycling
High discharge pressure Check for loss of condenser water or
blocked condenser fan or coil.
Defective overload relay Replace.
High suction temperature Reduce suction temperature by expansion
valve adjustment or provide
desuperheating.
Loose power or control circuit wiring
connection
Check all power and control circuit
connections.
Defective motor Check for motor ground or short. Replace
compressor, if either condition is found.
Compressor cycles on locked rotor
Low line voltage Check line voltage and determine location
of voltage drop.
Compressor motor defective Check for motor winding short or ground.
Single phasing Check voltage across all 3 legs at
contactor. Correct source problem.
Motor burnout
Check control panel for welded
contactor contacts or welded overload
contacts
Replace defective components
Table 23 Compressor and refrigeration system troubleshooting (continued)
Symptom Possible Cause Check or Remedy