(SCOP)=useful heat delivered/(loop pump energy+heat pump energy+distribution fan or pump energy)

The Tank (SCOP)=useful heat delivered/(loop pump energy+heat pump energy+distribution fan or pump energy)

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  • #19477
    Tex99
    Participant

    energyexpert; your factual advise is always appreciated.

    ……… from the net;

    (SCOP) = useful heat delivered / (loop pump energy + heat pump energy + distribution fan or pump energy)

    Question: (GSHP) 3 Ton COP3.5 —– “kwh consumed to produce 100.000btu of usable heat?”

    > GSHP) 3.5 COP/ 3 ton=16.7 amps+circulating water-pumps=4a & air blower=3.9a=24.6Ax 240VAC=5.90kw.(RLA) <

    #19491
    energyexpert
    Participant

    If I am following this, the 3 ton system actually delivers 38,000 BTUs/hr (rated) and requires 5.9 kW of power to run it. Running for one hour requires 5.9 kWhs.
    Using 5.9 kWhs with resistance heat (COP=1) would give (5.9 x 3,413) = 20,140 BTUs in one hour.
    38,000/20,140 = 1.89 COP
    So I do not know where the disconnect is. 38,000 BTUs delivered with a system rated at a COP of 3.5, should require 38,000/3.5/3,413 = 3.18 kWhs. Or 8.37 kWhs for 100,000 BTUs delivered.
    COP changes with changing conditions. I remember looking at at Trane 3 ton heat pump. At 47F it had a COP of 3.5. At 7F it had a COP of 1.84. So maybe the 5.9 kW required to deliver the 38,000 BTUs is under the worst expected (and maybe tested) conditions.
    David

    #19522
    Tex99
    Participant

    COP does not include other pumping or blower power being used in the system, only the compressor power.

    With a (COP) of 1,89, the kwh increases to 15.5 kwh to produce 100.000btu of useful heat.
    With a (COP) of 1.70, the kwh increases to 17.2 kwh to produce 100.000btu of useful heat

    …. It’s not a single simple formula, but there are ample web-sources detailing how to determine the theoretical COP of an “ideal” system under various conditions.
    (Unless you’re designing compressors & systems using a variety of refrigerants & coils you probably don’t care. Designing around a single manufacturer’s
    system & component guidelines you’d never need to crunch real math.)

    A 3ton compressor requires 16,7A+7.9A(water circulating pumps & fan) = > 48% increase of power to operate the total system <

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