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NetworkAIR FM DX 60 Hz Operation, Maintenance, and Troubleshooting76
Compressor fails to
start
• Cooling mode disabled
• Cooling setpoint too high
• Compressor circuit breaker is
tripped
• System is in alarm
• Head pressure alarm, high
pressure switch is open
• Low suction pressure
• Compressor thermal overload is
open
• Compressor failure
• Enable cooling mode.
• Adjust the cooling setpoint below the return
air temperature by at least 4
°F (2°C) to
activate the compressor or compressors.
• Check the compressor windings and verify
open or short to ground windings. Reset the
circuit breaker and check the compressor
contactor load side for proper voltage to the
compressor.
• Check front panel display for active system
alarms.
• For air cooled systems, check the condenser
coil for air-obstructions, fan operation, and
settings. Manually reset the high pressure
switch.
• For water cooled systems, check the condenser
water flow rate and water supply temperature.
Check the pressure drop across the heat
exchanger. Check and clean field installed
strainers. Check the water regulating valve,
actuator, and linkage for proper operation.
• For glycol cooled systems, check the fluid
cooler coil for air obstructions and proper fan
operation. Check the water flow rate and water
supply temperature. Check the pressure drop
across the heat exchanger. Check and clean
field installed strainers. Check water
regulating valve, actuator, and linkage for
proper operation.
• Check for a restriction in the filter drier.
• Check for power at the liquid line solenoid
coils. Check solenoid coil and valve operation.
• Check for proper TXV operation and
superheat.
• Check refrigerant charge, check system for
leaks.
• Verify the return air temperature is not below
68
°F.
• Check for low head pressure.
• Check compressor shell temperature. Check
compressor for open windings and allow
sufficient time for the compressor to cool
down to room temperature. After the thermal
overload resets, determine the cause of the
failure.
• Determine the cause of failure and replace the
compressor set.
Problem Possible Cause Corrective Action