This is quite dramatic isnt it? Its not at all good. When I first saw this type of thing on my 6kW Ecodan, I fitted a sensor of the discharge pipe from the compressor. This would at least confirm that liquid refrigeant is entering the compressor. Mine was. The next question is … what is the expansion valve doing at that time. I had an idea to look at the Expansion valve (LEV or EEV). I got as far as very carefully putting something like 2kohm (I think) resistors on the LEV signals, straight onto LEDs. This gives opening and closing pulse flashes. Next stage would have been an EmonTH with optical pulse sensor to count pulses. To know it the valve is opening or closing, a 2nd optical is needed… e.g. If ( LED2=on 10ms after LED1 pulse ; LEV opening; else LEV closing. It would be nice to see what a LEV was doing… but what will it tell us?? I would expect the LEV to be closing quite rapidly when the discharge temperature is so low (when heat output drops). However, maybe the sensors are oblivious to conditions, and the valve is opening up, making it worse. I dont actually have the knowhow to be able to configure an EmonTH with 2 optics, and the ability to read the state LED2 10ms after sensing LED1. How easy would this be to achieve? Can LEVs stick?? I dont know. However, if this were the case, we should see closing pulses with no response. Its still a thing I would like to complete. I’m sure something would be learnt
[Discussion about monitoring the Expansion Valve continues here:
Heat Pump Expansion Valve behaviour ]