The Tank › (SCOP)=useful heat delivered/(loop pump energy+heat pump energy+distribution fan or pump energy)
- February 2, 2013 at 10:20 am #19477Tex99Participant
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) <February 8, 2013 at 5:45 pm #19491energyexpertParticipant
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.
DavidFebruary 15, 2013 at 4:59 pm #19522Tex99Participant
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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