Emerson Liebert.PEX+ Series User Manual page 79

Symptom
Too much refrigerant charging
HP protection Electric valve improperly set
(water-cooled)
Water flow too big or temperature of input
water too low (water-cooled)
Refrigerant leaked
Low discharge
Fan speed controller of outdoor unit is
pressure
faulty, while the output voltage remains
100%, regardless of the change of
condensing pressure (air-cooled)
The suction and
Compressor reversed or compressor
discharge pressures do
internal air tightness failed
not change after startup
Insufficient refrigerant in the system
Filter too dirty
Filter drier clogged
Improper superheating degree
Defective element of the thermal
expansion valve faulty
Improper air flow distribution
Low condensing pressure
Belt slipped
Low suction pressure or
liquid returned
The single source cooling unit configured
with FC fan, its dehumidification
electromagnetic valve is closed
ESP is too large, air flow reduction
Liquid returned
Compressor too noisy
Lubricant loss
Fixture of compressor is not removed
Too high compression ratio
Compressor
over-temperature
Too high suction temperature
Liebert. PEX+Series Precision Air Conditioner
Potential causes
Chapter 8 Troubleshooting
Items to be examined or handled
Check whether the subcooling degree is too high
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
Check the water system
Locate the leakage point, repair it and add refrigerant
If the fan speed controller is found faulty, replace it
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
Check for leakage. Seal the leaking point and add
refrigerant
Replace the filter
Replace the filter drier
Regulate by strictly following the adjusting procedures of
the thermal expansion valve
Replace the thermal expansion valve
Check the air supply and return system
Check the condenser
Check the belt and make necessary adjustment or
replacement
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
Check the ventilation duct or air channel, evaluate the
unit ESP again
Refer to the handling methods of Low suction pressure or
liquid returned
Add lubricant
Remove the transportation fixture
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
Regulate the expansion valve or add proper amount of
refrigerant
User Manual
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