EER and COP question

Discussion in 'General Discussions' started by RonL, Feb 13, 2021.

  1. RonL

    RonL Member

    Another newbie type question concerning numbers.

    I was looking at comparable heat pumps to what I have now. (FHP 2.5 ton open loop) I checked against a Miami Heat Pump of the same size / style (single stage). The MHP has higher eer and cop but when I look at the running amps of the compressors and blowers, the mhp has higher values so it would seem to me it would be more costly to run. So how could its values be higher but yet cost more to run ? The btu of the mhp are 39k cooling and 27k heating..where the fhp is 37k cooling and 31.5 heating. So the mhp cools better but the fhp heats better. Fhp is eer of 19.1 and cop of 3.7, mhp is eer of 26 and cop of 4.1.
    Same cfm of 1000.
    Just not really understanding these ratings...
    Also the heating difference of 27k vs 31.5k. Would that make a real difference in run time ?
  2. gsmith22

    gsmith22 Active Member Forum Leader

    EER and COP are just an outcome of the point-in-time operating condition of the heat pump. Heat pump capacity (ie BTU/hr) is highly dependent on incoming water temp and flow as well as interior air temp and air flow. If all four of these values are the same (and most critically the incoming water temp is the same), then its a valid comparison point and you can compare BUT/hr and the resulting COP/EER at that point across brands. If the four values are different, then you are comparing apples to oranges (and thus capacity, EER, and COP will be different). Each manufacture should produce a specification chart showing heating and cooling capacities, electric used to get those capacities and the resulting COP/EER for specific incoming water temps. I would think with an open loop, your incoming water temp would be fairly constant over all seasons so you can probably focus on a specific incoming water temp (deep ground temp typically). its a little harder with a closed loop as the incoming water temp fluctuates through each season.

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