Symptom
Possible
Cause
Check Or Remedy
Cooling cycle too
short
Sensor
response
delay too
short
Increase sensor response delay. See Calibrate Sensors on page60.
Display freezes
and control pads
do not respond
Static
discharge
During period of low humidity, static electricity can cause the control program to freeze or display incorrect
information. Although this is unlikely, the control can be reset by cycling power from the disconnect switch.
Condensate
pump does not
operate
Open or short
circuit in
wiring
Find open or short circuit and repair power to pump.
Continuous
Cooling
Failed
temperature
sensor
Temperature display will indicate dashes. Check wiring from temperature/humidity board (remote sensors) to
the control board or from control board to wallbox. Replace temperature/humidity circuit board (remote
sensors) or wallbox.
Continuous
Heating
Dehumidification
Humidification
Shorted wiring
or failed
control board
Check wiring and/or replace control board.
Display Problem
Incorrect
wiring
Review Electrical Connections on page36. Verify VDC between 5 to 6 Volts at TB-3 Pin 1 (Ground) and TB-3 Pin 2
of the control board and wall box. If the transmit lines (TB-3 Pin 3 & 4) are not connected, only the POWER LED
will be lit. It will flash once every 10-12 sec. If T- is connected, but not T+, TX1 will flash approximately every 2-3
sec. And the POWER LED will flash once every 10-12 sec. If T+ and T- are reversed, the POWER LED and RX1
Will be lit and flash every 10-12 sec.
NOTE: Erratic operation of the unit could occur. If no LED is lit, there is no power or the +5VDC polarity is
reversed. If any of these conditions occur, remove power from the evaporator using the disconnect switch, and
correct wiring from the control board to the wall box.
NOTE: It may take up to 20 seconds for the display to appear on the wall box LCD after power is applied.
Table 13.1 Troubleshooting (continued)
Vertiv | Liebert Mini-Mate2—5 ton User Manual| 89
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