Problem Cause Remedy
Low compressor
capacity/ no cooling
Defective liquid line
solenoid valve
Check valve and coil; replace if necessary.
Plugged filter drier Check pressure drop across filter drier. Replace filter drier.
Low refrigerant charge
Check for normal system operating pressures. Refer to abnormalpressure
causes if applicable. Check for leaks. Proper refrigerant charge is very important
at low ambient operation.
Compressor noisy
Loose compressor or
piping support
Tighten clamps.
Compressor rotation in
reverse direction
Check for proper power phase wiring to unit and to compressor motor.
Pipe Rattle Loose pipe connections Check pipe connections and supports.
Compressor running
hot
Compression ratio too
high
Check for normal system operating pressures. Refer to abnormalpressure
causes if applicable.
Compressor motor
protectors tripping
or cycling
High discharge pressure Check for blocked condenser fan or coil.
High suction
temperature
Check expansion valve and hot gas bypass valve setting. Check liquid quenching
valve operation.
Loose power or control
circuit wiring connection
Check all power and control circuit connections.
Defective motor
Check for motor ground or short. Replace compressor if either condition is
found.
Compressor cycles
on locked rotor
Low line voltage Check line voltage and determine location of voltage drop.
Compressor motor
defective
Check for motor winding short or ground.
Single phasing Check voltage across all 3 legs at contactor. Correct source of problem.
Motor burnout
Check control panel for
welded contactor
contacts or welded
overload contacts.
Replace defective components.
Table 9.1 Troubleshooting (continued)
Vertiv | Liebert® PFD™ Installer/User Guide
32
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