Liebert 8 Tons, 50 & 60Hz user manual 8.0TROUBLESHOOTING, Troubleshooting

Troubleshooting

8.0TROUBLESHOOTING

Table 18 Troubleshooting

Symptom	Possible Cause	Check or Remedy
	No power to unit	Check voltage at input terminal block.
	Control voltage fuses (at	Locate and repair short. Replace fuses.
	transformer) open
Unit will not start	Float switch relay has closed	Check drain and line. Access through left panel. Power must be
	due to high water in the	cycled at the disconnect to reset. Check return air static pressure is
	condensate pan.	less than 0.3" wg.
		Check terminal 37 and 38 for jumper or N/C contact. Check pins P39-
	Jumper not in place	1 and P39-2 for jumper, or N/C firestat contact. Check pins P40-12
		and 1HWAR-Com for jumper or N/C smoke detector contact.
	“Cooling” is not displayed at	Adjust TEMP control setpoint and sensitivity to require cooling.
	the control panel.
	Short cycle prevention	Control software delays compressor 3 minutes cooling, from stop to
	control.	start
	Compressor contactor not	Check for 24 VAC ± 2 VAC at terminals TB2 to TB1 for Compressor 1;
		TB6 to TB5 for Compressor 2. If voltage, check contactor. If voltage,
No cooling	pulling in.
		check freeze stat (FR1 and FR2).
	Compressor high head	See below for cause.
	pressure.
	Plugged filter/dryer.	Replace filter/dryer.
	Low refrigerant charge.	Check pressure gauges. At low ambient temperatures, proper
		refrigerant charge is very important on units with Lee-Temp receivers.
	Insufficient air flow across	Remove debris from coil and air inlets.
	condenser coil
Compressor high	Water/Glycol-Cooled only:
head pressure	No fluid flowing through	Check fluid supply to regulating valve. Adjust valve if necessary.
	condenser.
	Condenser fan not operating	Check fan operation.
	DIP switch not set to enable	See DIP switch settings Table 17.
	humidifier option
	“HUMIDIFY” not displayed	Increase humidity control setpoint and sensitivity to require
	at control panel	humidification.
		Check voltage at 35-1 and 35-5 on interface board for 24 VAC ±2
	Defective board	VAC. If no voltage, check wiring and/or replace board. Check wiring
		from control panel to board.
Humidifier does
		Humidity display will indicate dashes. Check wiring from temperature/
not operate	Failed humidity sensor	humidity board to the control board and from the wall box to the
		control board. Replace wallbox or temperature/humidity circuit board
		(if remote).
	No water flow	Make sure switch is in Run position. Check humidifier water supply
		(including filter screen) and check nylon overflow line if canister is full.
	Canister fill rate is not	Check fill valve screen opening and capillary tube for obstructions.
	keeping up with the steam
		Check water supply pressure (minimum 10 psig).
	output
	DIP switch not set to enable	See DIP switch settings Table 17.
	reheat option
	“HEAT” not displayed at the	Increase temperature setpoint to require heating.
Reheat will not	control panel
operate
	Reheat safety open,	Check voltage at P34-4 or P34-6 to P34-10 on interface board for 24
	defective reheat contact or	VAC ± 2 VAC. If voltage, check reheat contactor and reheat safety. If
	defective board	no voltage, check wiring and/or replace board.
	Element is burned out	Turn off power. Check element continuity with Ohm meter.

58