Troubleshooting; Table 18 Troubleshooting - Liebert 8 Tons User Manual

8.0 T
ROUBLESHOOTING
Table 18

Troubleshooting

Symptom
No power to unit
Control voltage fuses (at
transformer) open
Float switch relay has closed
Unit will not start
due to high water in the
condensate pan.
Jumper not in place
"Cooling" is not displayed at
the control panel.
Short cycle prevention
control.
Compressor contactor not
pulling in.
No cooling
Compressor high head
pressure.
Plugged filter/dryer.
Low refrigerant charge.
Insufficient air flow across
condenser coil
Compressor high Water/Glycol-Cooled only:
head pressure No fluid flowing through
condenser.
Condenser fan not operating
DIP switch not set to enable
humidifier option
"HUMIDIFY" not displayed
at control panel
Defective board
Humidifier does
not operate
Failed humidity sensor
No water flow
Canister fill rate is not
keeping up with the steam
output
DIP switch not set to enable
reheat option
"HEAT" not displayed at the
control panel
Reheat will not
operate
Reheat safety open,
defective reheat contact or
defective board
Element is burned out
Possible Cause
Check voltage at input terminal block.
Locate and repair short. Replace fuses.
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.
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.
Adjust TEMP control setpoint and sensitivity to require cooling.
Control software delays compressor 3 minutes cooling, from stop to
start
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).
See below for cause.
Replace filter/dryer.
Check pressure gauges. At low ambient temperatures, proper
refrigerant charge is very important on units with Lee-Temp receivers.
Remove debris from coil and air inlets.
Check fluid supply to regulating valve. Adjust valve if necessary.
Check fan operation.
See DIP switch settings Table 17.
Increase humidity control setpoint and sensitivity to require
humidification.
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.
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).
Make sure switch is in Run position. Check humidifier water supply
(including filter screen) and check nylon overflow line if canister is full.
Check fill valve screen opening and capillary tube for obstructions.
Check water supply pressure (minimum 10 psig).
See DIP switch settings Table 17.
Increase temperature setpoint to require heating.
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.
Turn off power. Check element continuity with Ohm meter.
Check or Remedy
58
Troubleshooting