Screw Compressor Central Chiller
Chapter 6: Troubleshooting
68
Problem
Possible cause
Corrective action
Freeze control set higher than
temperature of liquid in
system. (Freezestat alarm)
Lower freeze control setting to
10°F (6ºC) below the leaving
temperature you want.
Remote Air cooled units:
Check
condenser fans for proper
rotation. Check for dirty
condenser. Check for condenser
air obstruction. Check for
blown fuses or bad condenser
fan motor.
High pressure refrigerant
cutout switch contacts open.
Water cooled units:
Check for
water valves turned on. Check
for dirty condenser. Check
water flow through condenser.
Allow time to cool and reset.
Check for high/low voltage.
Voltage must be within plus or
minus ten percent (±10%) of
nameplate rating.
Compressor internal overload
open. (Alarm)
Check for poor compressor
electrical connections.
Compressor contactor holding
coil open.
Low refrigerant pressure
switch contact open. (Low
pressure alarm)
Repair or replace.
Defective pump motor
interlock to PLC.
Repair or replace.
Compressor does not run.
Check active alarm screen.
Broken wire in the compressor
control circuit.
Locate and repair.
Freezestat control setting is too
high. (Freezestat alarm)
Lower set point to 10°F (6ºC)
below the leaving water
temperature you want with at
least 15 degrees differential.
Pump runs, compressor cycles at
two minute intervals. Check
alarm screen.
Refrigerant is too low.
Check refrigeration charge;
check refrigerant sight glass for
bubbles or a level in the glass.
Improper water/glycol mixture.
Be sure the antifreeze mixture
protection is right for the
process.
Defective freezestat control.
Replace.
Leaving water temperature is not
at set point.
Refrigerant charge is low.
Call service to find and repair
the leak. Add refrigerant.
