Compressor cutoff
Compressor starts and stops again
Problem Possible cause Remedy
Cutoff through lowpressure
switch
Suction pressure too low:
- Check the setting of the low pressure switch - Adjust the switching points or replace switch
- Suction valve of the compressor closed - Open suction valve
- Capacity of compressor too large - Check operating conditions
- Refrigerant deciency - Leak test / add refrigerant
- Filter / dryer in the liquid line blocked - Replace lter / dryer
- Expansion valve not functioning properly - Check the setting of the expansion valve
- Solenoid valve on the liquid line not opening - Check the control / function
Cutoff through highpressure
switch
Condensing pressure too high:
- Check the setting of the high-pressure switch - Adjust the switching points or replace switch
- Pressure valve of the compressor closed - Open the pressure valve
- Condenser fan not functioning - Check the control / replace motor
- Condenser fan is dirty - Cleaning of condenser
- Excessive refrigerant lling - Extract refrigerant to normal lling
- Non-condensible gases in refrigerant - Extract refrigerant and evacuate the
refrigeration plant / rell refrigerant
Cutoff through heatprotection
thermostat (accessory)
Discharge end temperatures is too high
- Operating limits of compressor exceeded
- Adapt the operating conditions
to the operating range
- Suction gas overheating - Check expansion valve / check
insulation on the suction side
- Refrigerant of the condenser insufcient - Check fan motors / Clean the condenser
- Valve plate damage - Replace valve plate
- Internal safety valve has opened - Replace safety valve
-> Check compressor and refrigeration plant
Determine and remove the cause for the
inadmissible high pressure in the high-
pressure side
Cutoff through control
thermostat
Temperature over / below the desired range Check operating points
Cooling control or other switch /
control devices are switched off
Setting / selection incorrect - Check control design
- Change control
Function / drive incorrect - Check drive / function
- Check cables, contacts etc.
2 I Fault diagnosis
Problem Possible cause Remedy
Overload / Motor safety switch
is tripped
Two phase run Ensure three phase run
Very unequal phase runs Determine and remove the cause