Air Source Heat Pumps

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16791112176

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  • paceinternet
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    In post #78 above by richardc1983 this "oversize" concept could be applicable to air to air heat pumps. Obviously, "correct" sizing is important for an operational temperature range.

    However, the air to water heat pump specifiers often recommend undersizing the heat pump, or to put it another way, not sizing it to cover the absolute known minimum temperature. They size it for an outdoor temperature range down to a level that is "cost effective". But they may also include another heat source to supplement the heat pump and allow it to operate below this level to an agreed minimum.

    There is not just one solution, and it is very appropriate to get a few suppliers to propose a solution for you. You should then assess the differences and understand what you are likely to get for what capital and running cost.

    As is said above, even leaders like Mitsubishi get complaints about installations not meeting expectations, so make sure your expectations are made clear, and if necessary accept that some solutions will be a compromise of capital cost against running cost.
    To exaggerate the point, the system may cost £5k to cover 364 days most years, but £8k to cover 365 days. Whereas that 1 day could be supplemented with £10 of direct heating electricity.

    Edit: whilst typing this, Cardew's post has appeared with very similar tones!
  • Kev_Dale
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    From reading some of the links and a little further research, it looks as though you can get an ashp unit for about £1k. The NIBE one I've been quoted is far in excess of this.

    So, what would you be looking to pay for a 8kW ashp unit only (forget the add ons, ie hot water tank etc for the minute)?
  • samtheman1k
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    Do you mean an air to air or an air to water hp?
  • Kev_Dale
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    Do you mean an air to air or an air to water hp?

    Air to water
  • paceinternet
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    There is an 8 kw unit for around £1000, but check the performance graph to understand what it delivers at various outside temperatures. Not much more for an 11 kw which gives you proportionately more at lower outside air temp.
    See also here for some alternative prices either side of 8 kw. I have no connection with this company, but there are few companies selling the equipment direct to end users to point you to. As you have said, the major brands are significantly more expensive.
  • richardc1983
    richardc1983 Posts: 2,157 Forumite
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    The cheaper units will have more basic control strategys and this will include the defrost control strategy, some units are more intelligent than others, some others will continue to run with reduced output even when there is lots of ice on the coil, which is not efficient or good as the output drops considerably. Other more expensive units such as VRV systems defrost whilst still maintaining heat output.

    The large number of people complaining shows its down to the people selling and installing units that are incompetent.

    ASHP allways oversize slightly for the worst case scenario.

    WATER TO AIR (not sure as havent got these)
    If you found my post helpful, please remember to press the THANKS button! --->
  • Cardew
    Cardew Posts: 29,038 Forumite
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    WATER TO AIR (not sure as havent got these)

    Novel concept!!;)
  • richardc1983
    richardc1983 Posts: 2,157 Forumite
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    is that sarcasm on a Friday Cardew! :P
    If you found my post helpful, please remember to press the THANKS button! --->
  • stevehead
    stevehead Posts: 215 Forumite
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    The large number of people complaining shows its down to the people selling and installing units that are incompetent.

    Sorry to correct you Rich, but there isn't a large number of people complaining at all, the quote simply says that 90% of those that did complain (unknown) were to do with inappropiatly sized systems.
    I do know that 6,000,000 domestic units are shifted every year in Japan (not exported). They're ashp mad over there!
  • richardc1983
    richardc1983 Posts: 2,157 Forumite
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    sorry mean to refer to the 90% of problems are caused by undersizing!
    If you found my post helpful, please remember to press the THANKS button! --->
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