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# Calculation of COP for Air to water heat pump.

• 15-12-2011 3:46pm
Registered Users, Registered Users 2 Posts: 225 ✭✭

Im trying to calculate the the COP of my heat pump.

The formula i was attempting to use is Q= mc(delta t)

But since this is an air to water system im not sure what temperatures i need to use in the formula.

I have sensors on the unit its self for the condenser and evaporator.
I also monitor the power being used by the heat pump.

Could anyone point me in the right direction?

I basically want to see how my cop is affected by the colder outside air temperature when im heating my buffer tank to 50 degrees C for my underfloor system.

• Registered Users Posts: 166 ✭✭

is 50 degrees not a bit high for underfloor??
from what i've been told for every degree above 35 that you go you lose 2-3% efficiency so in this case you are down30-45% efficiency and the efficiency also goes down by 2-3% for every degree below 7 degrees C that it is out side so you can work it from this but need to know what the COP is to start with not all are 400% some higher some lower....think efficiencies are up on seai website but not sure!!
I'm considering putting one of these in to my new build starting next year...how are you finding it?

• Registered Users, Registered Users 2 Posts: 176 ✭✭

That formula will give you the heating duty of the heat pump, not necessarily its COP.

All makers give the COP but as most people now realise this is usually at 7 ambient and an outlet temperature of 35 or so, you can request the data sheet which gives adjusted duties for lower ambients, all air to air heat pumps have this. I believe there is a move to wards using the american SEER system which gives seasonally adjusted efficiency.

al