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77NetworkAIR FM DX 60 Hz Operation, Maintenance, and Troubleshooting
Compressor noisy • Compressor or compressors may
be rotating in the wrong direction
• Liquid slugging
• High head pressure
• Verify the pressure differential across the
suction and discharge for each compressor. If
no differential is present, verify the correct
phasing to each compressor.
• Check for low evaporator superheat.
• Check operation of crankcase heaters.
• Verify liquid line solenoid valves close tightly
during the off cycle. Check for obstructions
which may prevent the valve from closing.
• Check operating head pressure.
Controls erratic or
inoperative
• Control transformer problem
• Loose or broken wiring
• Module configured incorrectly
• System is in alarm
• Check control transformers for proper input
voltage.
• Check control transformer secondary voltage.
Output should be within + or - 10% of rated
output.
• Check wiring for loose or broken connections.
• Set module configuration according to
nameplate and options selected.
• Check front panel display for active system
alarm.
Evaporator coil ices • Dirty or blocked evaporator coil
• Dirty or blocked air filters
•Low airflow
• Low evaporator superheat
• Low return air temperature
• Low refrigerant charge
• Clean evaporator coil.
• Check filters and replace as needed.
• Check for correct airflow setting.
• Check superhear and adjust to 10-15
°F.
• Verify the return air temperature is not below
20ºC (68
°F).
• Check for short cycling of cold supply air.
• Check subcooling and ensure it is at least
10-15
°F. Repair leak and recharge system.
Head pressure too
high
• Air cooled condenser malfunction
• Condenser water regulating valve
malfunction
• Overcharge of refrigerant
• Non-condensable in system
• Fluid cooler malfunction
• Fluid pump malfunction
• Low fluid flow
• Glycol concentration higher than
40%
• Check and clean the condenser coil. Check
condenser fan operation and settings.
• Check water regulating valve, actuator, and
linkage for proper operation.
• Remove excess refrigerant from system.
• Recover refrigerant charge, evacuate system
and recharge.
• Check and clean the fluid cooler coil. Check
fluid cooler fan operation.
• Check pump operation.
• For water cooled systems, check the condenser
water flow rate and water supply temperature.
Check pressure drop across the heat
exchanger. Check and clean field installed
strainers.
• For glycol cooled systems, check the water
flow rate and water supply temperature. Check
pressure drop across the heat exchanger.
Check and clean field installed strainers.
• Verify glycol concentration, reduce to
maximum 40%.
Problem Possible Cause Corrective Action