12
09665
-0
8.
20
18-
Gb
6 I Fault diagnosis
Refrigerant performance too low
Problem
Possible cause
Remedy
Suction pressure too high
- Evaporator iced up
- Remove the cause
- Expansion valve not functioning properly
- Check expansion valve setting;
replace valve, if necessary
- Lack of compressor capacity
- Check the function of the compressor by
evacuating to vacuum.
Check function of capacity regulator
(accessory)
- Shortage of refrigerant
- Run leakage test / refill
refrigerant
Suction pressure too low
- See „Cutoff through low-pressure switch“
- Checking
High-pressure too high
- See „Cutoff through high-pressure switch“
- Checking
High-pressure too low
- Condenser being cooled to much
- Adjust the control of condenser cooling
- Lack of compressor capacity
- Check compressor / Check the functioning
of capacity regulator
- Pressure laminations of valve plate leaking
- Replace valve plate
- By-pass between suction and discharge side
- Localize leak between the discharge and suc-
tion side and repair it
Problem
Possible cause
Remedy
Cutoff through high pressure
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 performance insufficient, con-
denser and fan motor contaminated
- Cleaning of condenser fins and fan
- Excessive refrigerant filling
- Extract refrigerant to normal filling
- Non-condensible gases in refrigerant
- Extract refrigerant and evacuate the
refrigeration plant / refill refrigerant
Cutoff through heat protection
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
- Condenser cooling insufficient
- Check fan motors / cleaning of condenser
- Valve plate damage
- Replace valve plate
- Internal decompression valve has opened
- Replace decompression 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
