Liebert himod - Table 21 Compressor and Refrigeration System Troubleshooting

Troubleshooting 59
High discharge pressure
Dirty condenser or drycooler fins Clean coil.
Condenser equipment not
operating
Check operation.
High refrigerant charge Check refrigerant charge.
Hot gas bypass valve adjusted
improperly
Adjust properly.
Fluid regulating valve adjusted
improperly
Adjust properly.
Low discharge pressure
Excessive fluid now through
condenser
Adjust fluid regulating valve.
Suction service valve partially
closed
Open the valve.
Faulty head pressure control
valve or condenser fan speed
control
Replace if defective.
Compressor rotation in reverse
direction
Check for proper power phase wiring to unit and to
compressor motor.
Low suction pressure
Insufficient refrigerant in system
Check for leaks, repair, and add refrigerant for air
cooled. Evacuate and recharge glycol cooled unit.
Dirty air filters Change filters.
Plugged filter-drier Replace filter.
Improper superheat adjustment Reset expansion valve for 20-35°F (11-19°C).
Defective expansion valve
sensing element
Replace element
Poor air distribution
Check duct work for closed dampers. Check for
under-floor restrictions at or near the unit.
Low condensing pressure Check head pressure control device.
Flooding
Defective or improperly set
expansion valve
Increase superheat or replace valve
Evaporator fan motor Correct problem or replace fan motor.
Low condensing pressure Check head pressure control device.
Low compressor capacity or
inability to pull down system
Leaking liquid line solenoid valve
or dirt in valve
Replace valve if clean; clean out valve if dirty.
Compressor rotation in reverse
direction
Check for proper power phase wiring to unit and to
compressor motor.
Compressor noisy
Loose compressor or piping
support
Tighten clamps.
Pipe rattle Loose pipe connections Check pipe connections
Compressor running hot Compression ratio too high
Check setting of high and low pressure switches.
Check condenser—is it plugged? Check that all
evaporator and condenser fans are operating
properly.
Compressor cycles intermittently
Low-pressure switch erratic in
operation
Check tubing to switch to see if clogged or crimped
Check for proper switch operation.
Insufficient refrigerant in system
Check for leaks, fix, and add refrigerant on air
cooled. Evacuate and recharge glycol cooled unit.
Suction service valve closed Open valve.
Insufficient fluid flowing through
condenser or clogged
condenser, or dirty air cooled
condenser coils
Adjust fluid regulating valve to condenser. Flush
the condenser.
Discharge service valve not fully
open
Open valve.
Table 21 Compressor and refrigeration system troubleshooting (continued)
Symptom Possible Cause Check or Remedy