Carnot 'theoretical COP' from which values?

Hardware Heatpump
1

Looking at my Grant R290 heatpump, I have an array of measured temp values (plus I know the real outdoor ambient), but I am at a loss to decide which ones to plug in to calculate the theoretical COP (which I’ll be lucky to get 50% of).

There is ambient, heatpump measured ambient, coil temp, suction temp, discharge temp (those two on the compressor), ExV temp, and finally LWT. Now the theoretical COP (TH/(TH-TC)) depends on two of those , but which two??

2

You need flow and ambient temperatures to calculate Carnot COP. I think LWT is flow temperature, assuming that’s measuring the water coming into the house. 50% is a good factor to use if not known.

3

Thanks I had already seen that. I just wonder whether any of the measured temps from the heatpump equate to T_Condensing, and T_Evaporating, rather than just applying a 6c or 2c offset to Ambient and LWT.

4

I don’t have an answer, but this related topic may be of interest:

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