© Danfoss | Climate Solutions | 2023.09
AX452438944357en-000301 | 5
2 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“
- Check
High-pressure too high
- See „Cutoff through high-pressure switch“
- Check
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 fins of valve plate leaking
- Replace valve plate
- By-pass between suction and discharge side
- Localize leak between the discharge and
suction 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 does not work
- Check the control / replace motor
- Condenser fan is dirty
- Cleaning of condenser
- 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 temperature 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 insufficient
- 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
