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Table 19 — Troubleshooting
SYMPTOMS CAUSE REMEDY
COMPRESSOR DOES
NOT RUN
Power line open Reset circuit breaker.
Control fuse open Check control circuit for ground or short.
Replace fuse.
High-Pressure Switch (HPS)
tripped
Move LOCAL/ENABLE-STOP-CCN switch to STOP
position then back to RUN or CCN position.
Tripped power breaker Check the controls. Find cause of trip
and reset breaker.
Loose terminal connection Check connections.
Improperly wired controls Check wiring and rewire.
Low line voltage Check line voltage. Determine location
of voltage drop and remedy deficiency.
Compressor motor defective Check motor winding for open or short.
Replace compressor if necessary.
Seized compressor Replace compressor.
COMPRESSOR CYCLES OFF
ON LOW PRESSURE
Loss of charge Repair leak and recharge.
Bad transducer Replace transducer.
Low refrigerant charge Add refrigerant.
COMPRESSOR SHUTS DOWN
ON HIGH PRESSURE
CONTROL
High-pressure control erratic in action Replace control.
Compressor discharge valve partially closed Open valve or replace if defective.
Condenser fan(s) not operating Check wiring. Repair or replace motor(s)
if defective.
Condenser coil plugged or dirty Clean coil.
UNIT OPERATES LONG OR
CONTINUOUSLY
Low refrigerant charge Add refrigerant.
Control contacts fused Replace control.
Partially plugged or plugged expansion
valve or filter driver
Clean or replace.
Defective insulation Replace or repair.
Service load Keep doors and windows closed.
Inefficient compressor Check valves. Replace if necessary.
SYSTEM NOISES Piping vibration Support piping as required.
Expansion valve hissing Add refrigerant.
Check for plugged liquid line filter drier.
Compressor noisy Check valve plates for valve noise.
Replace compressor (worn bearings).
Check for loose compressor holddown bolts.
COMPRESSOR LOSES OIL Leak in system Repair leak.
Mechanical damage (blown piston or
broken discharge valve)
Repair damage or replace compressor.
Crankcase heaters not energized
during shutdown
Replace heaters, check wiring and
crankcase heater relay contacts.
FROSTED SUCTION LINE Expansion valve admitting either too
much or too little refrigerant
Check cooler and compressor thermistors.
Test EXV.
HOT LIQUID LINE Shortage of refrigerant due to leak Repair leak and recharge.
FROSTED LIQUID LINE Shutoff valve partially closed or restricted Open valve or remove restriction.
COMPRESSOR DOES NOT
UNLOAD
Burned out coil Replace coil.
Defective capacity control valve Replace valve.
Miswired solenoid Rewire correctly.
Weak, broken, or wrong valve body spring Replace spring
COMPRESSOR DOES NOT
LOAD
Miswired solenoid Rewire correctly.
Defective capacity control valve Replace valve.
Plugged strainer (high side) Clean or replace strainer.
Stuck or damaged unloader piston or
piston ring(s)
Clean or replace the necessary parts.
EXV — Electronic Expansion Valve
Table 20 — Standard and Accessory Unloaders
UNIT
NO. OF STANDARD
UNLOADER(s)
NO. OF ACCESSORY
UNLOADERS
PERMITTED
Circuit A Circuit B
30GN040-070 1 1 1or2
30GN080-170* 211
30GN190-210* 011
*And associated modular units.
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