Vertiv | Liebert® DM | User Manual 103
Troubleshooting
Chapter 8: Troubleshooting
Troubleshooting is to be performed by trained and qualified service personnel. However, the checklists have
been provided for reference.
• Certain circuits carry lethal voltages. Only professional technicians are allowed to maintain the unit.
Extreme care and caution is required while troubleshooting the unit online.
• If jumpers are used for troubleshooting, remember to remove the jumpers after the troubleshoot. If not
removed, the connected jumpers may bypass certain control functions and increase the risk to the unit.
Table 8-1 represents the troubleshooting of the indoor unit of Liebert® DM units.
Table 8-1 Troubleshooting of the Indoor Unit
Symptom Possible Cause User Needs to Check Particulars or Processing Method
The unit does not
start
No power supply to the unit Check unit input voltage.
Circuit breaker of controller voltage
is open (at transformer)
Locate short circuit and reset circuit breaker.
Float switch relay has closed due to
high water level in the condensate
pump sump
Check if the drain piping and pipelines are clogged or
whether the condensate pump is damaged.
Jumper cables are not in place Check the state of the jumper cables on the control board.
No cooling
Compressor contactor not pulling in
Check for 220 Vdc ± 44 Vdc of coil. If the voltage is right,
check if the contactor is connected properly.
High compressor discharge
pressure
See if there is “High pressure alarm” and follow the
maintenance descriptions.
Plugged filter
Check if filter is clogged or damaged, if it is then clean or
replace the filter accordingly.
Low refrigerant charge
Use suction and discharge pressure gauge to check if
pressure is as per requirement. Also, see if there are any
evidents of bubbles exist in the sight glass.
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