Troubleshooting Industrial Refrigeration
Compressor will not start
No power to motor
Check power to and from fuses; replace fuses if necessary
Check starter contacts, connections, overloads, and timer (if
part winding start). Reset or repair as necessary.
Check power at motor terminals.
Repair wiring, if damaged.
Control circuit is open
Safety switches are holding circuit open. Check high
pressure, oil failure, and low-pressure switches. Also check
oil filter pressure differential switch is supplied.
Thermostat is satisfied.
Check control circuit fuses if blown; replace.
Check wiring for open circuit.
Motor "hums" but does not start
Low voltage to motor
Check incoming power for correct voltage. Call power
company or inspect/repair power wiring.
Check at motor terminals. Repair or replace as necessary.
Check at motor terminals. Repair or replace as necessary
Single-phase failure in the three-phase
Check power wiring circuit for component or fuse failure.
Compressor is seized due to damage
Remove belts or coupling. Manually turn crankshaft to check
Compressor is not unloaded
Check unloader system.
Compressor starts but motor Compressor has liquid or oil in
Check compressor crankcase temperature.
cycles off on overloads
Throttle suction stop valve on compressor to clear cylinders
and act to prevent recurrence of liquid accumulation.
Suction pressure is too high
Unload compressor when starting. Use internal unloaders if
Install external bypass unloader.
Motor control located in hot ambient.
Motor overloads may be defective or weak.
Check motor control relay.
Adjust circuit breaker setting to full load amps.
Bearings are "tight"
Check motor and compressor bearings for temperature.
Lubricate motor bearings.
Motor is running on single-phase
Check power lines, fuses, starter, motor, etc., to determine
where open circuit has occurred.
Compressor starts but short cycles
Low refrigerant charge
Check and add if necessary.
Driers plugged or saturated with