Table 21 Compressor And Refrigeration System Troubleshooting - Liebert Himod Operation & Maintenance Manual

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