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I'm wondering how I can calculate the overall thermal efficiency of my heating/refrigerator pump.

Actually I have this AC/heating pump unit from Samsung (P/N: AR09TXFYBWKNEE).

I've placed a power meter on the external unit, measuring kWh, kW, current, voltage and frequency and saving them in a datalogger.

(In addition to the installed power meter, I've also added temperature and humidity sensors inside and outside the room environment. I don't know if they are useful for that.)

I want to know how the machine, its working (in terms of efficiency) in relation to its nameplate thermal data. In other words, if the consumed energy, related (for example) to the heating capacity, is employed correctly to heat my 52 square meter room. I want to calculate a sort of "efficiency rating" of the cooling/heating system referred to the nameplate data using the acquired information and the respective nameplate info.

You guys, could please help me to find the correct formula in order to get that?

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Efficiency = heat moved versus energy consumed. For a heat pump this is either SEER or Coefficient of Performance. Heat moved compared to energy used should be around 2 to 5 in equivalent units (COP). SEER includes USA-standard units so it is a larger number, but more or less means the same thing.

So you need to measure the heat removed/added - mass flowrate times heat capacity times temperaure change. Measuring the air flow rate isn't easy but isn't impossible, there are hoods you can put over vents that do this, or you can make a box yourself with a cardboard box and hand-held propeller-things that measure air flow rates either mechanical or electronic. Do this for all vents. Mass flow rate = volumetric flow rate times air density.

Humidity doesn't really matter for heating other than getting the heat capacity of the air correct. For cooling you need to measure the humidity of inlet and outlet air to get the heat change right.

The outside temperature affects your system efficiency, so you'll want to control for that as well. I don't know about that model specifically, but most higher-end (which I assume Samsung is) split units like that use variable frequency compressors, so the efficiency will also change based on how hard it is working.

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