70 Chapter 8 Troubleshooting
Liebert. PEX+Series Precision Air Conditioner User Manual
Symptom
Potential causes
Items to be examined or handled
EC fan cannot
be started
EC fan failure
1) Check whether the fans L1, L2 and L3 are power-off, phase failure or
undervoltage;
2) Check whether the analog signals output from P51 meet 0 ~ 10Vac
requirements;
3) Check whether the motor is clogged (overcurrent);
4) Check whether the motor is over temperature;
5) Hall failure;
If the problem is related to the first three points, the motor will run automatically
after fixing the problem;
If the motor is over temperature, switch off the fan till the motor cools down, and
recover it by switching on;
If the problem is Hall failure, contact the manufacturer for maintenance
8.2 Compressor And Cooling System Troubleshooting
The troubleshooting of refrigerant is listed in Table8-2.
Table 8-2 Troubleshooting of compressor and cooling system
Symptom
Potential causes
Items to be examined or handled
Compressor cannot
start
Power is not on (shutdown)
Check the main power switch, fuse or circuit breaker and
the connection cable
Power overloaded and MCB tripped
Manual reset and check the average current
Circuit connection loosened
Fasten the connections
Compressor coils shorted
Check the motor winding and replace it if defects are
found
Contactor cannot close,
compressor cannot
start
No demand for cooling output
Check the iCOM controller state
High voltage switch action
Check the high voltage switch
Contactor failure
Check the contactor, and check whether the 24Vac
voltage is between E1 and P32-10 (compressor 1) and
P32-12 (compressor 2) terminals
Contactor closed, but
compressor cannot
start
Circuit breaker disconnected
Check the circuit breaker and the contactor, and measure
the circuit voltage
Compressor internal circuit breaker open
Check the compressor coils. If the coils are open, they
will reset automatically after they cool down
Compressor stops after
running for 5min (1min
~ 5min settable). Or
contactor opens
Refrigerant leaked, the LP switch cannot
close, or the pressure reading from the LP
sensor of the dual cooling unit is lower;
the reading is incorrect from the LP
sensor of the dual cooling unit
1) Check the suction pressure;
2) Check the cable containing LP switch;
3) Check whether the LP sensor reading and actual
pressure meet ±0.3bar requirement (the HP sensor value
can be read from the SERVICE MENUS/DIAGNOSTICS,
which displays the absolute pressure)
Dual cooling/free cool
unit. When the
room/setting
temperature checked to
display refrigeration
requirement, but
without refrigeration
output within 10min, the
compressor will stop
running
In compressor operation, the antifreezing
protection will be generated for shutdown
Check the system and air channel to find out the reason
why LP is too low
HP protection
Condenser clogged
Temperature of input water is too high or
the water flow if too small (water-cooled)
Clean the condenser or BPHE;
Check the water system
Condenser system does not start
For air-cooled series, check the condensing fan; for
water-cooled series, check water system. Check the
operation procedures
