I have F20 error on my LA-MI heat pump. What does this mean?

Applicable to models:  LA6MI, LA9MI, LA12MI, LA16MI


Issue:  Error code F20 shown on the display. No heat, compressor is stopped.  


What this means: F20 means the compressor overheating protection mechanism has activated to protect the system.

Action: Engineer will need to investigate by following the information below:

Heat pump must be safely isolated from mains supply before carrying out any electrical work! Where mains voltages are being measured, this should only be carried out by suitably qualified personel.  

Note that only F-GAS qualified engineers are legally allowed to work on the system if they are leak checking, connecting to the refrigerant system or changing refrigerant components! 


Location of CN-TANK temperature probe on compressor:
Location of CN-TANK connector plug on main Refrigerant PCB:

Temperature probe should be disconnected and the resistance checked against the probes known temperature.

Malfunction Decision Conditions:

During operation of cooling and heating, when temperature above 112°C is detected by the compressor tank

temperature sensor.


Malfunction Caused:

1 Faulty compressor tank temperature sensor.

2 2/3 way valve closed.

3 Refrigerant shortage (refrigerant leakage).

4 Clogged expansion valve or strainer.

5 Faulty main Refrigerant PCB.

6 Faulty compressor.


Abnormality Judgment:

Continue 4 times in 30 minutes. 



Possible parts, depending on engineer diagnosis: 

• Electronic Expansion Valve

LA6MI / LA9MI part: X-2511026

LA12MI / LA16MI part: No Longer Available

• Compressor temperature sensor "CN-TANK" for LA6MI or LA9MI part: X-2511020.
Same sensor can be used for LA12MI / LA16MI but cable may need to be extended. 


• Compressor

LA6MI / LA9MI part: X-2511011

LA12MI / LA16MI part: X-2511040
(Note LA-MI does not employ a filter dryer, so if replacing the compressor, the system must be throughly vacuumed).


• Main Refrigerant PCB, aka "Outdoor PCB" (part number depends on model of heat pump)
LA6MI part: X-2511024
LA9MI part: X-2511038
LA12MI part: X-2511044
LA16MI part: X-2511057

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