Troubleshooting
59
Table 23 Compressor and refrigeration system troubleshooting
Symptom Possible Cause Check or Remedy
Compressor will not start
Power off Check main switch, fuses or CBs and
wiring
Current overload open Re-set units with overload option
manually. Allow compressor to cool for
internal overloads to reset.
Loose electrical connections Tighten connections
Compressor motor burned out Check and replace compressor if
defective.
Compressor will not operate,
contactor not pulling in
No call for cooling Check monitor status.
Solenoid valve not energizing Hold screwdriver over solenoid and check
for magnetic field. This indicates solenoid
is energized.
Low pressure switch not making contact Check gas pressure - manually energize
low pressure switch.
Compressor will not operate,
contact not pulling in
High pressure switch open Reset switch. Refer to other refrigeration
troubleshooting suggestions.
Compressor contactor pulled in but
compressor will not operate
Blown fuse or tripped CB Check for line voltage after fuses or CBs,
and after contactors.
Compressor runs for three minutes
then stops; contactor drops out.
Low pressure switch not closing Check for low gas pressure. Compressor
is running on Positive Start Kit (air cooled
systems only)
Liquid line solenoid valve not opening Check magnetic field to see if energized.
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.
Water regulating valve adjusted
improperly
Adjust properly.
Low discharge pressure
Excessive fluid flow 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 for water/glycol unit.
Dirty air filters Change filters.
Plugged filter-drier Replace filter.
Improper superheat adjustment Reset expansion valve for 10-15
°F
(6-8°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.
Slipping belts Inspect and adjust
