Liebert DM User Manual page 67

60 Chapter 7 Troubleshooting
Symptom
Low exhaust
pressure
The suction and
exhaust pressures
do not change after
startup
Low suction
pressure or liquid
returned
Compressor too
noisy
Compressor
over-temperature
Symptom
Dehumidification
ineffective
Symptom
Humidiifcation
ineffective
Possible causes
Water flow too big or temperature of input
water too low (water-cooled)
Refrigerant leaked
Fan speed controller of outdoor unit is faulty,
while the output voltage remains 100%,
regardless of the change of condensing
pressure (air-cooled)
Compressor reversed or compressor internal
air tightness failed
Insufficient refrigerant in the system
Air filter too dirty
Filter drier clogged
Improper superheating degree
Sensor of the expansion valve faulty
Improper air flow distribution
Low condensing pressure
Belt slipped
Liquid returned
Bearing worn out due to insufficient lubricant
Fixture of compressor or pipes loosened
Too high compression ratio
Suction temperature too high
Table 7-3 Troubleshooting of dehumidification system
Possible causes
No dehumidification demand from the control
system
Compressor contactor does not close
Compressor does not start, fuse blown or
circuit breaker tripped
Hot gas bypass valve not closed (single
compressor system)
Table 7-4 Troubleshooting of infrared humidifier
Possible causes
Check the water supply
No water in the Check the water supply solenoid valve
water pan Check the state of the high water-level switch / water-level regulating valve
Check that the water supply pipe is not clogged
No humidification
Check the state of the controller
demand
Check the contactor, and check the circuit voltage of the fuse or circuit breaker
The humidification
Check the opened safety devices of the humidifier: water pan over-temperature
contact does not
protection switch and lamp over-temperature protection switch. Use a jumper to
close shot terminals P35-6 and P35-5. If the contactor closes, replace the
series-connected safety device, and remove the jumper
Humidifier lamp
Replace the lamp
burned
DM Series 16kW Air Conditioner User Manual
Handling method
Adjust the water flow regulator
Check the cooling water system
Locate the leakage point, repair it and add refrigerant
If the fan speed controller is found faulty, replace it
If compressor reversed, exchange any two L lines of the
compressor. If the compressor internal air tightness failed,
replace the compressor
Check for leaks. Seal the leaking point and add refrigerant
Replace the air filter
Replace the filter drier
Regulate by strictly following the adjusting procedures of
the thermal expansion valve
Replace the expansion valve
Check the air supply and return system
Check for condenser fault
Check the belt and make necessary adjustment
Refer to the handling methods of "Low suction pressure or
liquid returned"
Add lubricant
Fasten the fixture
Check the settings of the HP switch and LP switch, and
make sure the condenser is not clogged
Check that the fans of the evaporator and condenser are
normal
Regulate the expansion valve or add proper amount of
refrigerant
Handling method
Check the control system
Refer to the compressor related Table 7-2
Refer to the compressor related Table 7-2
Or check the fuse, or the circuit breaker and the contacts,
and check the line voltage
Check the control circuit related to the hot gas bypass
valve
Handling method