42
Chapter 4
B
Compressor will
not start—hums
but trips on thermal
protector
1. Improperly wired.
Check against wiring diagram and wire
properly.
2. Low voltage to compressor.
Turn off system until proper voltage is
restored.
3. System component, such as thermostat
or control/contactor, not functioning
properly.
Refer to the OEM service information.
4. Compressor electrical problems:
a. Compressor motor has a winding
open or shorted.
b. Start capacitor not working properly.
c. Relay does not close.
a. See “Identifying Compressor
Electrical Problems” on page 47.
b. Same as “a”.
c. Same as “a”.
5. Liquid refrigerant in compressor.
Add crankcase heater and a suction line
accumulator. It is difficult to determine how
liquid refrigerant got into the compressor.
A crankcase heater along with a suction-
line accumulator will prevent liquid
refrigerant from getting into the
compressor.
6. Internal mechanical trouble in
compressor.
See “Checking for Adequate Compressor
Pumping” on page 83.
C
Compressor starts,
but does not switch
off of start winding
1. Improperly wired.
Check against wiring diagram and wire
properly.
2. Low voltage to compressor.
Turn off system until proper voltage is
restored.
3. Compressor electrical problems:
a. Compressor motor has a winding
open or shorted.
b. Relay failing to open.
c. Run capacitor not working properly.
a. See “Identifying Compressor
Electrical Problems” on page 47.
b. Same as “a”.
c. Same as “a”.
4. Discharge pressure too high.
If this is a water-utilizing system, see
“Servicing or Troubleshooting Water-
Utilizing Systems: Preventing Explosions”
on page 39. Also refer to the OEM service
information.
5. Internal mechanical trouble in
compressor.
See “Checking for Adequate Compressor
Pumping” on page 83.
Complaint
Possible Causes
Response
Troubleshooting Chart- continued
