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Author Topic: Heat pump CoP check, something seems off?  (Read 2807 times)
Stig
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« Reply #15 on: April 03, 2018, 10:18:18 AM »

The house meter measures the actual power by multiplying the voltage and current together.  Your clamp is only measuring the current and doesn't know its phase wrt the voltage.

Checking your clamp-on meter vs. your house meter will give you an idea of the total power factor of your house, you'd need to switch everything else off except the heat pump to do the test for just the heat pump's power factor.  That might be inconvenient...
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marshman
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« Reply #16 on: April 03, 2018, 10:39:49 AM »

Agree on the power factor thing BUT The figures from Kensas own datasheets do not add up. The ones on my Thermia Duo data sheet do..  I/p x COP = O/p 

Even assuming a power factor of 0.8 (it shouldn't be worse than this really) it is still consuming 2.1 kW (assuming indicated 2.6kW on power meter).  Something doesn't add up in my opinion, or the measured input power is way off for other reasons (such as assuming 240V input when the mains voltage is much lower at  say 226V) That coupled with the power factor could make the numbers work (just) - but still doesn't answer the spec. sheet difference.

Roger
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3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
geoheated
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« Reply #17 on: April 03, 2018, 08:40:48 PM »

Did 4 tests measuring the apparent power factor between the house meter and the heat pump clamp-on meter.

Its coming it quite reliably at 0.77 each time. Seems a bit lower than expected, but that does factor in the clamp-on meter accuracy as well as an overall correction/power factor.


So that now corrects my initial results to:

When measuring 2.65kW, actual was closer to 2.65*0.77 = 2.04kW

For B6/W35 (actual conditions) the datasheet stated output is 7.9kW with a CoP = 4.77.

I am however still only getting:

7.9 / 2.04 = CoP 3.87

Gettting there, needs more investigating yet... I still agree with Roger that the datasheet isnt clear.


Noticed near the top of the datasheet, it also states "power consumption" at 2.1 with no units (assume this is kW) for B0W35, with a CoP of 4.13, so you would assume that the output would therfor be 2.1*4.13 = 8.67kW ?

But the other page of the same datasheet says B0W35 for the heat pump gives 6.5kW output and CoP = 4.13. So you would assume that meant input power of 6.5/4.13 = 1.57kW.

Go figure? Maybe time to ask Kensa :-)







« Last Edit: April 03, 2018, 08:53:49 PM by geoheated » Logged
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