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Heating and cooling: Advice on air source heat pumps and solar heating

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  1.  
    • CommentAuthorKarhedron
    • CommentTimeJan 30th 2009
     
    Hello all,

    We are in the process of extending our house, and we have to get rid of our nasty old boiler. We were planning on going for a straight condensing boiler, but then, having done a bit more research, we're not so sure. We want to put in solar water heating - could we use this for house central heating too? WE have a fab south facing roof that get the sun almost all day. However, if it is possible to run heating off of the sun, we would still need something for during the night. We've heard about air source heat pumps, but can't really find anything out about them. If we got one, would we need a conventional boiler too, or would it be instead of? How do they work? Do they take up much space? Does anyone have an idea of costs? We've planning permission for a single storey rear and side extension to our 1930's semi. We'd like to fit a green roof on the extension, and have underfloor heating - would the heat exchange/solar thing work? We've been told that Thermomax are a very good brand of tubes - does anyone have any experience or advice? Would we need a water softenertoo (we live in Basingstoke, which has the hardest water in the UK).
  2.  
    ASHP instead of gas boiler, yes. They work exactly the same as your fridge - they pull the heat out of air and 'launder' it somewhere else - via the black squiggly bit at hte back of your fridge, or via a heating system (rads or u/floor (pref)).

    As to CoP (Coefficient of performance - kWh of heat out for each kWh of elec to run the pump), and energy politics, there are lots of opinions. Keith/Admin - can Karhedron view the history?

    I lived in Basingstoke a veeeeeeery long time ago. Most of what I knw got demolished, though my old house still exists. It is near a roundabout, just off a ring road (really!).

    Search for 'thermal stores' on this forum. Solar in the day can = heat at night.
    • CommentAuthorMiked2714
    • CommentTimeJan 31st 2009 edited
     
    ASHP instead of gas boiler (on mains gas) NO (in my opinion)

    You can get SOME of your heating from solar energy if you have enough panels but you need to design the system so that you can dump excess heat in the summer. You will need a vented thermal store to integrate the heat sources: have a look through many past threads on this topic.

    ASHP issues. Wasn't there a sticky about this? Do you plan to have underfloor heating and no radiators? Will there be a noise issue from the fans? Can the heat pump provide the heating load of your house? I'd strongly suggest finding some happy heat pump owners with houses similar to yours before going down that route.

    Water softener is a separate issue. If you have hard water then yes, they are brilliant. Ours uses two bags of salt per year and easily pays for itself in reduced consumption of washing powder and limescale remover. Do not however fill your heating system with softened water.

    UPDATE: The but about ASHPs is part of the welcome to guests sticky
    • CommentAuthorSimonH
    • CommentTimeFeb 1st 2009
     
    Take a look at this thread...

    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3352

    I've been looking into ASHP, it works, can outperform gas boilers over the whole heating season, but when the air temp drops below about 5 degrees a [mains] gas boiler will be cheaper to run and have lower emissions.

    So best seems to be have both and switch over when one become more efficient than the other. However it's not too easy to work out how to do it!

    Should mean you use gas on say 20-40 days per year, and ASHP the rest - when your solar hasn't produced enough heat. Since I've been thinking about it I've been much more interested in what the outside temp is. Not been above 5 degrees much since December, especially at night when E7 is available.

    Simon
    • CommentAuthorMiked2714
    • CommentTimeFeb 2nd 2009
     
    Simon

    Wouldn't you still need to run your AHSP entirely on E7 for it to be worthwhile? In which case you'd need a correctly sized thermal store to provide heat at peak rate times? From the thread, it looks like this is assuming heating via UFH only.

    Mike
  6.  
    Mike 2714 said: ''AHSP instead of gas boiler NO (in my opinion)''. Maybe I was a bit too 'shorthand'. Karhedron said: '' If we got one, would we need a conventional boiler too, or would it be instead of? ''. My answer was meant to indicate that you *can* use it instead of a boiler (SimonH's later comments note that it may not be that efficient - agreed!), not that you *should*. That was why I put the bit about CoP and energy politics (and perhaps should have mentioned financial common-sense, too!

    N
    • CommentAuthorMarkK
    • CommentTimeFeb 2nd 2009
     
    if you have gas, you will never buy an ashp..it's too much money.

    solar's good tho, but only for hot water...for space heating you still need your boiler.
    • CommentAuthorMiked2714
    • CommentTimeFeb 3rd 2009
     
    Cheers Nick, I think we're all in agreement!

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