GEA FK40/390 K Maintenance Manual page 12

6 I Fault diagnosis
Problem
Cutoff through high pressure
switch
Cutoff through heatprotection
thermostat (accessory)
Cutoff through control
thermostat
Refrigerant performance too low
Problem
Suction pressure too high
Suction pressure too low
High-pressure too high
High-pressure too low
12
Possible cause
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
- Condenser fan not functioning
- Condenser fan is dirty
- Excessive refrigerant filling
- Non-condensible gases in refrigerant
Discharge end temperatures is too high
- Operating limits of compressor exceeded
- Suction gas overheating
- Suction gas overheating
- Valve plate damage
- Internal decompression valve has opened
Temperature over / below the desired range
Possible cause
- Evaporator iced up
- Expansion valve not functioning properly
- Lack of compressor capacity
- Shortage of refrigerant
- See „Cutoff through low-pressure switch"
- See „Cutoff through high-pressure switch"
- Condenser being cooled to much
- Lack of compressor capacity
- Pressure laminations of valve plate leaking
- By-pass between suction and discharge side
Remedy
- Open the pressure valve
- Check the control / replace motor
- Cleaning of condenser
- Extract refrigerant to normal filling
- Extract refrigerant and evacuate the
refrigeration plant / refill refrigerant
- Adapt the operating conditions
to the operating range
- Check expansion valve / check
insulation on the suction side
- Check expansion valve / check
insulation on the suction side
- Replace valve plate
- Replace decompression valve
-> Check compressor and refrigeration plant
Determine and remove the cause for the
inadmissible high pressure in the high-
pressure side
Check operating points
Remedy
- Remove the cause
- Check expansion valve setting;
replace valve, if necessary
- Check the function of the compressor by
evacuating to vacuum.
Check function of capacity regulator
(accessory)
- Run leakage test / refill
refrigerant
- Checking
- Checking
- Adjust the control of condenser cooling
- Check compressor / Check the functioning
of capacity regulator
- Replace valve plate
- Localize leak between the discharge and
suction side and repair it