American Power Conversion FM, DX Problem, Possible Cause, Corrective Action, Compressor noisy

Problem	Possible Cause	Corrective Action
Compressor noisy	• Compressor or compressors may	• Verify the pressure differential across the
	be rotating in the wrong direction	suction and discharge for each compressor. If
		no differential is present, verify the correct
		phasing to each compressor.
	• Liquid slugging	• 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.
	• High head pressure	• Check operating head pressure.
Controls erratic or	• Control transformer problem	• Check control transformers for proper input
inoperative		voltage.
		• Check control transformer secondary voltage.
		Output should be within + or - 10% of rated
		output.
	• Loose or broken wiring	• Check wiring for loose or broken connections.
	• Module configured incorrectly	• Set module configuration according to
		nameplate and options selected.
	• System is in alarm	• Check front panel display for active system
		alarm.
Evaporator coil ices	• Dirty or blocked evaporator coil	• Clean evaporator coil.
	• Dirty or blocked air filters	• Check filters and replace as needed.
	• Low airflow	• Check for correct airflow setting.
	• Low evaporator superheat	• Check superhear and adjust to 10-15°F.
	• Low return air temperature	• Verify the return air temperature is not below
		20ºC (68°F).
	• Low refrigerant charge	• 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	• Air cooled condenser malfunction	• Check and clean the condenser coil. Check
high		condenser fan operation and settings.
	• Condenser water regulating valve	• Check water regulating valve, actuator, and
	malfunction	linkage for proper operation.
	• Overcharge of refrigerant	• Remove excess refrigerant from system.
	• Non-condensable in system	• Recover refrigerant charge, evacuate system
		and recharge.
	• Fluid cooler malfunction	• Check and clean the fluid cooler coil. Check
		fluid cooler fan operation.
	• Fluid pump malfunction	• Check pump operation.
	• Low fluid flow	• 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.
	• Glycol concentration higher than	Check and clean field installed strainers.
	40%	• Verify glycol concentration, reduce to
		maximum 40%.

NetworkAIR FM DX 60 Hz Operation, Maintenance, and Troubleshooting 77