Chapter 8 Troubleshooting 71
Liebert. PEX+Series Precision Air Conditioner User Manual
Symptom
Potential causes
Items to be examined or handled
HP protection
Too much refrigerant charging
Check whether the subcooling degree is too high
Electric valve improperly set
(water-cooled)
Check whether the LP sensor reading and actual
pressure meet ±0.6bar requirement (the HP sensor value
can be read from the SERVICE MENUS/DIAGNOSTICS,
which displays the absolute pressure)
Check whether the BPHE electric ball valve is normal
Low discharge
pressure
Water flow too big or temperature of input
water too low (water-cooled)
Check the water system
Refrigerant leaked
Locate the leakage point, repair it and add refrigerant
Fan speed controller of outdoor unit is
faulty, while the output voltage remains
100%, regardless of the change of
condensing pressure (air-cooled)
If the fan speed controller is found faulty, replace it
The suction and
discharge pressures do
not change after startup
Compressor reversed or compressor
internal air tightness failed
If compressor is reversed, exchange any two L lines of
the compressor. If the compressor internal air tightness is
failed to recover, replace the compressor
Low suction pressure or
liquid returned
Insufficient refrigerant in the system
Check for leakage. Seal the leaking point and add
refrigerant
Filter too dirty
Replace the filter
Filter drier clogged
Replace the filter drier
Improper superheating degree
Regulate by strictly following the adjusting procedures of
the thermal expansion valve
Defective element of the thermal
expansion valve faulty
Replace the thermal expansion valve
Improper air flow distribution
Check the air supply and return system
Low condensing pressure
Check the condenser
Belt slipped
Check the belt and make necessary adjustment or
replacement
The single source cooling unit configured
with FC fan, its dehumidification
electromagnetic valve is closed
Check the status of the dehumidification electromagnetic
valve when the system has no dehumidification
requirement. Examine whether there is 24Vac voltage
between P34-8 and E1, if there is not, it indicates that the
dehumidification electromagnetic valve is closed, you
should check the relevant cables of the electromagnetic
valve;
Check whether the air flow lose switch connection is
normal. Examine whether there is 24Vac voltage between
P36-7 and E1 after power-on, if there is not, you should
check whether the air flow lose switch is damaged
ESP is too large, air flow reduction
Check the ventilation duct or air channel, evaluate the
unit ESP again
Compressor too noisy
Liquid returned
Refer to the handling methods of
Low suction pressure or
liquid returned
Lubricant loss
Add lubricant
Fixture of compressor is not removed
Remove the transportation fixture
Compressor
over-temperature
Too high compression ratio
Check the settings of the HP switch and LP switch, and
make sure whether the condenser is clogged;
Check that the fans of the evaporator and condenser are
normal
Too high suction temperature
Regulate the expansion valve or add proper amount of
refrigerant
