Heat pumps

Discuss environmental matters here, and compare notes on what renewable energy systems might be best for you.
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jeba
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Heat pumps

Post by jeba »

I´m getting conflicting info about the efficiency of heat pumps. Some forum members recommended them and e.g. this technician advises against them: https://www.youtube.com/watch?v=GhAKMAcmJFg
Is there a practical and economical way to measure their efficiency? What are your experiences, if any, in the mountainous regions North of Paphos?
J B
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Re: Heat pumps

Post by J B »

Do we arrume that you refer to your A/C units used for heating?

IIRC, for every 1Kw of electricity used it gives 2½ to 3 Kw of heat

Your location is irrelevant to the laws of science :lol: ;)
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jeba
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Re: Heat pumps

Post by jeba »

J B wrote: Sun Jan 23, 2022 10:52 am Do we arrume that you refer to your A/C units used for heating?
Only partly correct. I might also want to heat a pool.
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Devil
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Re: Heat pumps

Post by Devil »

We have to be careful with our terminology here. The guy in your video is not talking about a heat pump system but, at least in the first minutes, a glorified aircon. A true heat pump can heat a whole house (or cool it). Feel the serpentine on the back of you're fridge; it's warm because it's extracted heat from the inside of the fridge. This is the principle of pumping heat out of the fridge into the air. A true heat pump does the same on a much larger scale and can be very efficient, but costly. To keep up the analogy of the fridge, imagine that you're using a heat pump in summer where you are cooling the house but heating something outside. The crux of that question is the word "something". Dealing with the whole house (possibly including hot water) is a big undertaking. If you are lucky and have a perennial watercourse running outside your garden, you can put a serpentine into that and that would be the equivalent of the black pipes on the back of your fridge. However, that is rarely practical in Cyprus. The next best thing is to get a hydrological survey and find if there is a large perennial underground water flow somewhere under your garden and, with permission, have your heat exchanger buried in it. The usual option in Cyprus is to bury a hefty length of pipe about 4 or 5 m underground. The "hefty length" will be determined by the combination of the heat to be transferred and the thermal conductivity of the soil (measured in summer). This is hardly an undertaking to be tackled lightly for heating/cooling a whole house with, say, two or three bedrooms or more.

Beware of systems which are inadequate for heating and cooling a whole house. In particular, it is possible for a small installation to have the outside pipework in a relatively small air cooled serpentine for the outside heat exchanger, with or without fan assistance, but you will not get the 350 to 400% efficiency (hence the guy in the video suggesting don't do it – he may be right unless you do it properly and at a high capital expense).
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Devil
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Re: Heat pumps

Post by Devil »

I have just read your second post and my first reaction is that the size of your heat pump and hence the length of buried pipework may be prohibitive. It's not a good idea to use the swimming pool as the outside heat exchanger as you would boil in summer and freeze in winter!

Maybe you could think more in terms of the solar system for heating the pool.
jeba
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Re: Heat pumps

Post by jeba »

Devil wrote: Sun Jan 23, 2022 12:11 pm I have just read your second post and my first reaction is that the size of your heat pump and hence the length of buried pipework may be prohibitive. It's not a good idea to use the swimming pool as the outside heat exchanger as you would boil in summer and freeze in winter!

Maybe you could think more in terms of the solar system for heating the pool.
What about an air-to-air heat pump? Will it still work efficiently at low outside temperatures ( say between 0 and 5 degrees)?
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Devil
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Re: Heat pumps

Post by Devil »

It will work but its efficiency will be way down
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