OM 135
PFS 155C - 315C
43
Troubleshooting Chart
PROBLEM
POSSIBLE CAUSES
POSSIBLE CORRECTIVE STEPS
Compressor will not nun
1. Main power switch open
1. Close switch
2. Unit S1 system switch open
2. Check unit status on MicroTech display. Close switch.
3. Circuit switch PSI PS2 in pumpdown position.
3. Check circuit status on MicroTech display Close switch
4. Evaporator flow switch not closed.
4. Check unit status on MicroTech display Close switch.
5. Circuit t breakers open
5. Close circuit breakers
6. Fuse b own or circuit breakers tripped
6. Check electrical circuits and motor windings for shorts or
grounds. Investigate for possible overloading. Check
for loose or corroded connections Reset breakers or
replace fuses after fault s corrected.
7. Unit phase voltage monitor not satisfied
7. Check unit power wiring to unit for correct phasing.
Check voltage
8. Compressor overload tripped
8. Overloads are manual reset. Reset overload at button on
overload. Clear alarm on MicroTech.
9. Defective compressor contactor or contactor coil
9. Check wiring Repair or replace contactor
10. System shut down by safety devices
10. Determine type and cause of shutdown and correct
problem before attempting to restart.
11. No cooling required
11. Check control settings. Wait until unit calls for cooling
12. Motor electrical trouble
12. See 6 7 8 above.
13. Loose wiring
13. Check circuits for voltage at required points. Tighten all
power wiring terminals
Compressor Noisy or Vibrating
1. Compressor internal problem'.
1. Contact McQuayService.
2. Liquid injection not adequate.
2. Check to assure Iiquid line sightplass is fulI during
steady operation
Compressor Overload Relay
Tnpped or Circuit Breaker Trip or
Fuses Blown
3. Low voltage during high load condition.
3. Check supply voltage for excessive voltage drop
4. Loose power wiring.
4. Check and tighten all connections.
5. Power line fault causing an unbalanced voltage
5. Check supply voltage
6. Defective or grounded wiring in the motor.
6. Check motor and replace if defective.
7. High discharge pressure
7. See Corrective Steps for high discharge pressure
Compressor Will Not Load or
Unload
1. Defective capacity control solenoids
1. Check solenoids for proper operas on
2. Unloader mechanism defective.
2. Replace.
Compressor Liquid Injection
Protection Trip
3. Liquid injection solenoid did not open at start
3. Check and replace Iiquid injection solenoid
4. Inadequate liquid to liquid injection at start due to a
clogged filter-dryer or low charge
4. Check liquid inject on line sightglass. If flashing check
filter-dryer and unit charge
5. Inadequate liquid to liquid injection during run
5. Check liquid injection line sightglass If flashing check
filter-dryer and unit charge Discharge pressure too low
Troubleshooting chart continued on next page
