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Author Topic: Fitting my heat pump  (Read 1930 times)
nuts and bolts
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Posts: 8

« on: October 04, 2007, 03:59:01 PM »

Hi all,
I'm looking for guiding hands again on a subject which I have only a  cursory knowledge - mainly from this forum.
I plan to fit a heat pump in the near future (using LPG at present which is prohibitive) for space heating only (DHW is mainly solar).
I hope to use water from the village burn pumped directly through the heat pump as this is cheaaper than a bore hole and supposedly more efficient.
I have an old sandstone built house which is not paarticularly well insulaated at present (I  hope to improve on this a bit but there aare several technical problems that belong in another post).
heat distribution is by conventional rads. and there is no scope for UFH.
The run form the burn to the heat pump is 55metres and the head is 3 metres.
My heat loss calculations suggest a 9kW heat pump will be required.

My queries are:
1 what volume of water needs to be pumped through the heat pump - ( is this dependent on delta T?)
2 What kind of pump is suitable to pump the water from the burn?
3 What is the best way to screen the intake - is it sufficient to  use a reasonablly coarse mesh  - if so then is there danger of dammage to pump or heat pump from silting?
4 What size of pipe would I need - presumably dependent on 1 above.
5 Although the burn never freezes totally I would imagine that it gets pretty cold at the coldest times of the year (lowest recorded air temp of -21 degrees C) - does this afffect the efficiency or sizing of the heat pump?
6 would I be better installing a hot air circulation system instead of rads?

Any information or thoughts would be gratefully received.
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« Reply #1 on: October 04, 2007, 04:53:12 PM »

The usual system is to bury the pipes in the stream  and transfer heat that way.  Possibly though you could use a DX system through a heat exchanger using your method.   The DX system is supposed to give about 5:1 and produce higher temperatures, the difference from the normal system is that the refrigerant is used for bi=oth input and output circuits.     Heat pumps prefer to work through a buffer tank and stay producing at full output while on.  I think this is the only choice with DX systems.  Radiators should be OK but you have to accept that they will be lower temperature.   It does mean trying to find an effient pump which has a good COP figure at higher output temperature.

DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
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