American Power Conversion DX, FM Problem, Possible Cause, Corrective Action, Head pressure too

Problem	Possible Cause	Corrective Action
Head pressure too	• Low refrigerant charge	• Check subcooling and ensure it is at least
low	• Condenser fan settings too low	10-15°F. Repair leak and recharge system.
		• Adjust condenser fan setpoints.
	• Condenser water regulating valve	• Check water regulating valve, actuator, and
	malfunction	linkage for proper operation.
	• System requires flooded	• Install flooded condenser controls.
	condenser control during low
	ambient conditions
Humidifier	• Humidification mode disabled	• Enable humidification mode.
inoperative	• Humidification setpoint too low	• Raise humidification setpoint.
	• Humidifier is in alarm	• Check front panel display for active humidifier
		alarms.
	• Humidifier canister full of	• Replace humidifier canister.
	sediment	• Check for shorted wiring, excessive current
	• Blown fuse or fuses
		draw, and proper input voltage. Replace fuse
		or fuses with the specified type.
	• No power to electrodes	• Check contactor, wiring, and connections.
Humidity control is	• Excessive outside air infiltration	• Reduce outside air infiltration.
not tight enough	• Lack of proper room vapor barrier	• Install vapor barrier materials on floor, walls,
		and ceiling as needed.
	• Humidification/dehumidification	• Check and adjust humidification and
	setpoints not close enough	dehumidification setpoints.
	• Humidifier sensitivity % setpoint	• Reduce humidifier sensitivity % setpoint.
	too high	• Tune the PID loop for accurate
	• Dehumidification PID loop is not
	properly tuned	dehumidification operation.
	• Return air humidity does not	• Check for short cycling of cold supply air.
	reflect actual room condition	• Check air distribution for deficiencies.
		• Consider using remote sensor control.
		Note: Be certain to purchase the correct
		temperature and humidity probe. Check when
		ordering that your equipment is compatible.
Module powered but	• System is off	• Turn the System on.
will not operate	• Remote shutdown or input contact	• Check input contact configuration settings.
	is active
	• System is in alarm	• Check front panel display for active system
		alarms.
	• System is idle (in group mode)	• Check group mode configuration settings.
Reheat elements	• Reheat mode disabled	• Enable reheat mode.
inoperative	• Reheat setpoint too low	• Raise reheat setpoint.
	• Thermal cut out switch is open	• Reset switch and check for proper airflow
		across heater.
	• Blown fuse or fuses	• Check for shorted wiring, excessive current
		draw, and proper input voltage. Replace the
		fuse or fuses with the specified type.
	• SCR controller malfunction	• Verify operation of SCR controller.

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