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Air Source Heat Pumps

Discussion in 'Plumbing and Central Heating' started by Jever, 23 Sep 2014.

  1. Jever

    Jever

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    Hi,

    I recently visited a new development site (I like to nose around for new ideas) and learned that some new houses are now being heated by 'air source heat pumps'.

    It's a bit like an air conditioning unit that stands in your back garden and extracts heat from the atmosphere (apparently down to temperatures as low as -15°C) and then uses the heat to heat the house and water supply.

    I have to say I was amazed by this idea and also very excited at the thought of never having another oil delivery. Apparently, they run best in well insulated houses via underfloor heating.

    It sounds almost too good to be true....so there has to be some drawback, surely? My suspicion is that they don't necessarily get the water as hot as a traditional oil/gas system, hence the average shower is tepid at best.

    Does anyone here have any real life experience of these systems? I'd really like to know what the downside is.

    TIA

    Jever
     
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  3. Nozzle

    Nozzle

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    You can get ground source heat pumps too - basically an air conditioning unit in reverse. I can't comment how good/bad they are.

    Nozzle
     
  4. Agile

    Agile

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    The main problem is they work least when its cold outside and you want the most heat from them.

    The other problem is that they will in most cases only heat to about 60 C above the air temperature hence why they are best ( or in most cases only suitable at all ) with under floor heating.

    Heating water can be augmented by electricity to get the water up to a useful temperature.

    Another disadvantage is that, although expensive, they only come with a very short warrantee like 12 months is some cases.

    Tony
     
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  5. Richardthe3rd

    Richardthe3rd

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    I've installed all types matey. A Geothermal HP(ground source) is basically the best. But you need a large area of land to take advantage of these systems & they're expensive to install.

    An Air Source HP are mostly supplemented by leccy as stated, but like all HPs, work well in well insulated homes.

    All HPs work at their optimum with underfloor heating as they'll normally operate a lower mean water temperature, which suits a thermodynamic system.
    HTH
     
  6. bell824

    bell824

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    and 7 years or up to 10 in others
     
  7. bell824

    bell824

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    expensive yes, large area of land no (borehole!)
     
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  9. bell824

    bell824

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    get the best of both world's fit a hybrid!

    most ASHP's won't work in poor insulated homes but in a hybrid scenario can save lot's of £'s working alongside an oil/LPG setup.

    at the moment Gas vs ASHP is a no brainer gas win's on price but against LPG/oil then ASHP's or hybrid's is the way to go!
     
  10. flameport

    flameport

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    The noise for one.

    Check round the back of any shop or office to get the general idea.

    Now multiply that by an entire estate of houses.
     
  11. Richardthe3rd

    Richardthe3rd

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    Yes bell-end, also very expensive to install. However a running river, large pond or Loch is ideally suited to a Geothermal HP system.

    I recently completed a social housing project where ASHPs were used, semis & terraced houses. No noise issues there. If you listen to the ex used car salesmen that are now selling green products, they'll tell you all sorts of drivel.
     
  12. bell824

    bell824

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    No need to get touchy turdy, I did say expensive YES.
    And I hate used car salesmen as well, See we have something in common.
     
  13. cjard

    cjard

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    ASHPs and GSHPs have a rating known as the coefficient of performance that relates to the amount of heat they can extract from the source versus the amount of electrical energy they take to run

    e.g. A 1kw electric fire produces 1kw of heat and takes 1kw of electricity to do so so its COP is 1
    An ASHP or GSHP takes 1kw of electricity and uses it to extract 3kw of heat, so its COP is 3

    It's kinda like getting the heat output of a 3kw electric fire for the price of a 1kw one

    If youre a green nut, it doesn't really stackup in some terms against an efficient boiler because a power station that burns gas can only turn about a third of the heat energy in the gas, into electricity - you buy 1kw of electricity (that's cost 3kw of gas for the power co to produce) and use it to run your xSHP which recovers 3kw of heat for the 1kw of electricity. Overall no useful planet saving gain was made (unless you use photovoltaic solar panels to help provide the electricity tto run the xSHP) versus an efficient boiler which burns 3kw of gas and generates about 3kw of heat

    There are government incentives to use these systems; every kw of heat you generate earns you some amount of pence from the government and it's intended that over the 7 years the payments will be made for (so long as the govt carries on affording the policy) the payments will pay for the install of what is often a massively expensive (compared to a normal gas boiler) install

    Other drawbacks are as others have mentioned, cost of installation and cost of equipment. xSHPs also have water systems that run at 40 to 45 degrees, asking for any more ruins the COP and makes it not much better than just running an immersion heater so these systems are totally unsuited to radiators unless the rads are massive. They also have to use an immersion heater to heat the whole system up to 65 degrees plus on a regular basis to kill germs in the system. Ordinary heating systems run at this temp as a matter of course so don't have the "problem"

    xSHPs are most recommended for people living off the mains gas grid, rural areas etc as an alternative to oil delivery. Those people who have them say they don't have to pay for oil or LPG any more - true, but they do have to pay for electricity, the pumps consume rather a lot of it, and what is used to generate electricity in this country? Gas and oil.. (And coal and nuclear) so to think that an xSHP will isolate you from rising gas and oil prices is something of a fallacy

    I know a housebuilder who installs a lot of ground source and he says they work well, but theyre no magic bullet..
     
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