8 Trouble Shooting
8.1 Competent Persons Trouble Shooting Guide
PROBLEM POSSIBLE CAUSE ACTION
Compressor does not operate Interlock circuit for chilled water
pump is open
Electrical protective devices have
tripped.
Incorrect wiring connection for
compressor power source
Check the pump contactor. Repair or replace, if
necessary.
Check the pump.
Locate and rectify the fault. Reset the "ON" switch.
Interchange two of three terminals R, S and T at the
main power source terminals.
Compressor stopped by high
pressure switch
Excessively high discharge pressure
Malfunction of high pressure switch
See "High Discharge Pressure"
Readjust the setting or replace if defective.
Compressor stopped by
overcurrent relay
Excessively high discharge pressure
and suction pressure
High or low voltage, single-phase or
phase imbalance
Loose electrical connections
Faulty overcurrent relay
See "High Discharge Pressure" and "High Suction
Pressure".
Check the power supply line and contactors. Repair, if
necessary.
Tighten the loose electrical connection or repair, if
necessary.
Replace overcurrent relay.
Compressor stopped by freeze
protection thermistor
Excessively low chilled water outlet
temperature
Defective thermistor
Shortage of chilled water flow
Air in water circuit
Check for excessively low setting of the chilled water
tempearture switch..
Check for malfunction of the thermistor. Replace, if
necessary.
Check chilled water pump.
Purge air.
Compressor stopped by internal
thermostat or discharge gas
thermostat
High or low voltage, single-phase or
phase imbalance
Excessive superheat
Defective element
Excessive high discharge pressure
and low suction pressure
Check the power supply line and contactors. Repair, if
necessary.
Check for refrigerant leakage
Check the internal thermostat for correct operation.
See "High Discharge Pressure" and "High Suction
Pressure".
Insufficient cooling High discharge pressure or low
suction pressure
Improper thermostat setting
Defective unload mechanism
See "High Discharge Pressure" and "Low Suction
Pressure".
Readjust the setting.
Adjust unload mechanism. Repair or replaceany
defective components.
Noisy compressor Slugging due to liquid flooding back
to compressor
Worn internal components
Check the superheat of suction gas. Ensure the
superheat is within range.
Replace the compressor.
Unloaded does not function Faulty thermistor
Faulty solenoid valve
Faulty unloader mechanism
Adjust the emperature setting t.
Replace the thermistor.
Check the coil in the solenoid valve.
Check oil passage for clogging.
Check the unloaded system parts in the compressor.
8-1
035-21786-100 Rev. 1 (0909)
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