Air-Cooled Screw Compressor Chiller Installation, Operation and Maintenance Manual 60 Hertz

Troubleshooting Chart

Table 55, Troubleshooting

PROBLEM POSSIBLE CAUSES

1. Main power switch open.

2. Unit S1 system switch open.

3. Circuit switch PS1, PS2, PS3, PS4 in pumpdown position.

4. Evap flow switch not closed.

5. Circuit breakers open.

6. Fuse blown or circuit breakers tripped.

Compressor will not run.

7. Unit phase voltage monitor not satisfied.

8. Compressor overload tripped.

9. Defective compressor contactor or contactor coil.

10. System shut down by safety devices.

11. No cooling required.

12. Motor electrical trouble.

13. Loose wiring.

POSSIBLE CORRECTIVE STEPS

1. Close switch.

2. Check unit status on MicroTech display. Close switch.

3. Check circuit status on MicroTech display. Close switch.

4. Check unit status on MicroTech display. Close switch.

5. Close circuit breakers.

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 is corrected.

7. Check unit power wiring to unit for correct phasing. Check voltage.

8. Overloads are manual reset. Reset overload at button on overload.

Clear alarm on MicroTech.

9. Check wiring. Repair or replace contactor.

10. Determine type and cause of shutdown and correct problem before attempting to restart.

11. Check control settings. Wait until unit calls for cooling.

12. See 6,7,8 above.

13. Check circuits for voltage at required points. Tighten all power wiring terminals

Compressor Noisy or Vibrating

1. Compr. Internal problem.

2. Liquid injection not adequate.

1. Contact McQuayService

2. Check to assure liquid line sightglass is full during steady operation.

Compressor

Overload Relay

Tripped or Circuit

Breaker Trip or

Fuses Blown

1. Low voltage during high load condition.

2. Loose power wiring.

3. Power line fault causing unbalanced voltage.

4. Defective or grounded wiring in the motor.

5. High discharge pressure.

1. Check supply voltage for excessive voltage drop.

2. Check and tighten all connections.

3. Check supply voltage.

4. Check motor and replace if defective.

5. See corrective steps for high discharge pressure.

Compressor Will

Not Load or Unload

1. Defective capacity control solenoids.

2. Unloader mechanism defective.

1. Check solenoids for proper operation. See capacity control section.

2. Replace.

Compressor Liquid

Injection Protection

Trip

1. Liquid injection solenoid did not open at start.

2. Inadequate liquid to liquid injection at start due to a clogged filter drier or low charge.

3. Inadequate liquid to liquid injection during run.

1. Check and replace liquid injection solenoid.

2. Check liquid injection line sight glass. If flashing check filter drier and unit charge.

3. Check liquid injection line sightglass. If flashing check filter-drier and unit charge. Discharge pressure too low. Protect condenser coil from wind.

High Discharge

Pressure

1. Discharge shutoff valve partially closed.

2. Noncondensables in the system.

3. Fans not running.

1. Open shutoff valve.

2. Purge the noncondensables from the condenser coil after shutdown.

3. Check fan fuses and electrical circuits.

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High Discharge

Pressure

4. Fan control out of adjustment.

5. System overcharged with refrigerant.

6. Dirty condenser coil.

7. Air recirculation from outlet into unit coils.

8. Air restriction into unit.

4. Check that unit setup in MicroTech matches the unit model number.

Check MicroTech condenser pressure sensor for proper operation.

5. Check for excessive subcooling above 30oF (-1.1oC). Remove the excess charge.

6. Clean the condenser coil.

7. Remove the cause of recirculation.

8. Remove obstructions near unit.

Low Discharge

Pressure

Low Suction

Pressure

High Suction

Pressure

1.

2.

3.

4.

Wind effect a low ambient temperature.

Condenser fan control not correct.

Low section pressure.

Compressor operating unloaded.

1. Protect unit against excessive wind into vertical coils.

2. Check that unit setup in MicroTech matches the unit model number.

Check SpeedTrol fan on units with SpeedTrol option.

3. See corrective steps for low suction pressure.

4. See corrective steps for failure to load.

1. Inadequate refrigerant charge quantity.

2. Inadequate liquid to liquid injection at start. Clogged liquid line filter-drier.

3. Expansion valve malfunctioning.

4. Insufficient water flow to evaporator.

5. Water temperature leaving evaporator is too low.

6. Evaporator tubes fouled.

7. Evaporator head ring gasket slippage.

8. Glycol in chilled water system

1. Check liquid line sightglass. Check unit for leaks. Repair and recharge to clear sightglass.

2. Check pressure drop across filter-drier. Replace cores.

3. Check expansion valve superheat and valve opening position.

Replace valve only if certain valve is not working.

4. Check water pressure drop across the evaporator and adjust gpm.

5. Adjust water temperature to higher value.

6. Inspect by removing water piping. Clean chemically.

7. Low suction pressure and low superheat both present may indicate an internal problem. Consult factory.

8. Check glycol concentration

1. Excessive load - high water temperature.

2. Compressor unloaders not loading compressor.

3. Superheat is too low.

1. Reduce load or add additional equipment.

2. See corrective steps below for failure of compressor to load.

3. Check superheat on MicroTech display. Check suction line sensor installation and sensor.

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