UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

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  • Andy_WSM
    Andy_WSM Posts: 2,217 Forumite
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    richardc1983 wrote: »
    YOu say your loft is always warmer than outside thats crazy... (not that i dont believe you)

    Had to go away and get the scientific answer as to why a loft is always warmer than the outside air :D

    Radiative cooling! http://en.wikipedia.org/wiki/Radiational_cooling

    A loft won't be subject to this and will hold a certain amount of heat from the day time in the materials of the build (i.e. the tiles).

    Also, with regards - do I have a big loft?

    Bigger than most houses as I live in a bungalow so am spread out a bit more, rather than living in a box.


    Right now, outside air 8.1C, Loft 9.5C, Lounge 22C.
  • richardc1983
    richardc1983 Posts: 2,157 Forumite
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    I understand why a loft is warmer than an outside air, due to heat being lost into the loft from the house below.

    What I am saying is though that working in air conditioning we would never install an outdoor unit inside unless the air supply to the outdoor unit was ducted from outside then ducted back outside.

    The reason being is that once its extracted heat from the loft it then starts to cool the loft even further due to the enclosed space.

    As I have said before I have come across previously units that have been installed in lofts and temperatures have just dropped further and further until the unit tripped out on a fault due to the unit working too hard.

    Have you got a picture of the install or a link to the type of unit you have?
    If you found my post helpful, please remember to press the THANKS button! --->
  • Andy_WSM
    Andy_WSM Posts: 2,217 Forumite
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    richardc1983 wrote: »
    I understand why a loft is warmer than an outside air, due to heat being lost into the loft from the house below.

    What I am saying is though that working in air conditioning we would never install an outdoor unit inside unless the air supply to the outdoor unit was ducted from outside then ducted back outside.

    The reason being is that once its extracted heat from the loft it then starts to cool the loft even further due to the enclosed space.

    As I have said before I have come across previously

    Maybe so, but I live on the coast so it's never likely to get THAT cold here that it is of concern. The other night it was -4C out, the loft got down to -1C. The unit will run to -5C so plenty of lee way there and -4C is very cold for here!

    It's not like the pump runs continuously either. For every 30 minutes it is on it is off for 10, unless I have drained the hot water tank, but again, that would be very rare.

    Richard, what can I tell you - it works!
  • Andy_WSM
    Andy_WSM Posts: 2,217 Forumite
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    richardc1983 wrote: »

    Have you got a picture of the install or a link to the type of unit you have?

    Here you go: http://www.trianco.co.uk/activair.cfm

    I have the 5KW unit.
  • richardc1983
    richardc1983 Posts: 2,157 Forumite
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    Im not saying that it doesnt work, im just saying standard practice is never to install a unit in an enclosed space but if it works and you monitor loft temperature then thats great, im pleased it works for you.

    All i mean is that before I have come across previously units that have been installed in lofts and temperatures have just dropped further and further until the unit tripped out on a fault due to the unit working too hard.

    Have you got a picture of the install or a link to the type of unit you have?

    Your loft must have a very good supply of fresh air for the temperature to not even lower when the unit is switched on.
    If you found my post helpful, please remember to press the THANKS button! --->
  • Andy_WSM
    Andy_WSM Posts: 2,217 Forumite
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    richardc1983 wrote: »
    Your loft must have a very good supply of fresh air for the temperature to not even lower when the unit is switched on.

    It's always windy here (coast again!) so the loft is a bit breezy at times but I only have standard ventilation under the eves and a couple of vent tiles on each side of the roof.

    Next project (when the Government allow it) is a wind turbine to capitalise on the wind and run the heat pump for free.
  • richardc1983
    richardc1983 Posts: 2,157 Forumite
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    Have you a link to the unit you have?
    If you found my post helpful, please remember to press the THANKS button! --->
  • Andy_WSM
    Andy_WSM Posts: 2,217 Forumite
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    richardc1983 wrote: »
    Have you a link to the unit you have?

    Yes, I posted it above :D
    Andy_WSM wrote: »
    Here you go: http://www.trianco.co.uk/activair.cfm

    I have the 5KW unit.
  • albyota
    albyota Posts: 1,106 Forumite
    Andy, you are obviously very happy with it, I have to agree with Richards concerns RE installed in the loft, but if your happy, thats OK. have you been able to monitor the running costs yet, would be interested to know how much its costing you to heat the bungalow and hot water...what size bungalow? rooms?
    There are three types of people in this world...those that can count ...and those that can't! ;)

    * The Bitterness of Low Quality is Long Remembered after the Sweetness of Low Price is Forgotten!
  • Andy_WSM
    Andy_WSM Posts: 2,217 Forumite
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    albyota wrote: »
    Andy, you are obviously very happy with it, I have to agree with Richards concerns RE installed in the loft, but if your happy, thats OK. have you been able to monitor the running costs yet, would be interested to know how much its costing you to heat the bungalow and hot water...what size bungalow? rooms?

    I posted this elsewhere, so to save me posting again, here's a copy & paste. I can't remember if I mentioned that the bungalow is 2 bed and very well insulated (Good insulation is far more important than heating!)
    Andy_WSM wrote: »
    Simon, my gas boiler packed up a year ago, so I took to using my A/C (Air - Air pump) to heat the house (this had already been installed in the Summer) and whilst it was "OK" I found it drafty at times. The running costs though were better than my gas bills. I used to pay ~ £200 for a Winters gas, but the air-air heat pump only cost £180 to run this Winter and it was a lot colder this Winter than previous years. I was however heating water by electric separately and not monitoring the cost of that.

    However...As I didn't like the drafty heat from the A/C, just over a week ago I purchased an air to water pump and connected it to my old central heating system and water tank. RESULT! Best investment ever! I have posted some details here: http://forums.moneysavingexpert.com/showthread.html?t=1464827

    Summary - I have all radiators on thermostatic valves, The heat pump is set to shut down at 48C (and does so frequently) - room temperatures are set at between 18C & 23C and all are being maintained comfortably. The unit is only 5KW, but the house isn't big and is extremely well insulated, so I don't need a huge amount of heat. Oh, I also leave it on 24/7 so that at no point has it got to work hard to heat the house from cold. I guess if I was only going to run it morning and night I'd need a bigger pump, but I have a chaotic work pattern/life style so 24/7 heat has always suited me best.

    Running costs - first impressions are good. The maximum it has cost in a 24 hour period is £2.20, it was -4C out overnight though. Today has been warmer and it has cost £0.66 for the last 12 hours! These costs include a tank of hot water, which is plumbed in as priority over the heating.

    My Dad is now looking into a heat pump for his property in Devon where there is no gas available. A 3 bed house would probably need the 11KW unit (or bigger) though.

    Hope this helps.
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