Heating System Troubleshooting - Liebert PEX+ Series User Manual

44 Chapter 7 Troubleshooting
Symptom
Compressor
cannot start
compressor
cannot work
Big noise of
compressor
Note: The cooling and dehumidifying demand is the precondition for judging the potential causes listed in this table

7.4 Heating System Troubleshooting

See Table 7-4 for troubleshooting heating system.
Symptom
Heating system
does not operate,
and the contactor
does not close
Contactor
closed, no
heating effect
Table 7-3 Troubleshooting of compressor and cooling system
Potential causes
Power is not on (shutdown)
Circuit connection loosened
High pressure switch action
Check air discharge temperature sensor
Check low pressure sensor
Contactor failure
MCB disconnected
Liquid returned
Lubricant loss
Fixture of compressor is not removed
Table 7-4 Heating system troubleshooting
Potential causes
Auxiliary relay failure of heater
Heating system safety equipment disconnection
Power failure of heater
Heater burnout
Liebert. PEX+Series Precision Air Conditioner
Items to be examined or handled
Check if the main power switch or MCB and the connection cable
are normal
Fasten the connections
Check if there is a high pressure alarm with reference to chapter
5
Check if Low/High TEMP alarm of air discharge exists with
reference to chapter 5
Check if there is coil frost or low pressure alarm in history alarms
with reference to chapter 5 to confirm if refrigerant leaks
Check if the contactor has 24Vac drive input
Check the MCB and the contactor, and then measure the circuit
voltage
Refer to the handling methods of Low suction pressure or liquid
returned
Add lubricant
Remove the transportation fixture
Items to be examined or handled
Check if the LED besides the relay is on and if the circuit
is correct
Check if the manual reset switch is opened and check if
the auto reset switch is damaged
Check if the heating MCB is closed;
When the heating contactor is closed, check if the L1, L2
and L3 voltages of contactor are normal
Cut off the power to checkthe heater
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