Liebert 50 & 60Hz User Manual

No power to unit

Check voltage at input terminal block.

Control voltage fuses (at 

transformer) open

Locate and repair short. Replace fuses.

Float switch relay has closed 

due to high water in the 

condensate pan.

Check drain and line. Access through left panel.   Power must be 

cycled at the disconnect to reset. Check return air static pressure is 

less than 0.3" wg.

Jumper not in place

Check terminal 37 and 38 for jumper or N/C contact. Check pins P39-

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 

the control panel.

Adjust TEMP control setpoint and sensitivity to require cooling.

Short cycle prevention 

control.

Control software delays compressor 3 minutes cooling, from stop to 

start

Compressor contactor not 

pulling in.

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, 

check freeze stat (FR1 and FR2).

Compressor high head 

pressure.

See below for cause.

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 

condenser coil

Remove debris from coil and air inlets.

Water/Glycol-Cooled only: 

No fluid flowing through 

condenser.

Check fluid supply to regulating valve. Adjust valve if necessary.

Condenser fan not operating

Check fan operation.

DIP switch not set to enable 

humidifier option

See DIP switch settings Table 17.

“HUMIDIFY” not displayed 

at control panel

Increase humidity control setpoint and sensitivity to require 

humidification. 

Defective board

Check voltage at 35-1 and 35-5 on interface board for 24 VAC 

±2 

VAC. If no voltage, check wiring and/or replace board. Check wiring 

from control panel to board.

Failed humidity sensor

Humidity display will indicate dashes. Check wiring from temperature/

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 

keeping up with the steam 

output

Check fill valve screen opening and capillary tube for obstructions. 

Check water supply pressure (minimum 10 psig). 

DIP switch not set to enable 

reheat option

See DIP switch settings Table 17.

“HEAT” not displayed at the 

control panel

Increase temperature setpoint to require heating.

Reheat safety open, 

defective reheat contact or 

defective board

Check voltage at P34-4 or P34-6 to P34-10 on interface board for 24 

VAC 

± 2 VAC. If voltage, check reheat contactor and reheat safety. If 

no voltage, check wiring and/or replace board. 

Element is burned out

Turn off power. Check element continuity with Ohm meter.