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Ground Source Heat Pumps

1.1K replies 315.5K views
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Replies

  • lovesgshplovesgshp Forumite
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    welda wrote: »
    Spot on Chippy, system basically sucks out more heat energy that can be replaced by normal solar activity. Bore hole and surrounding area is froze!!

    :beer:
    Wrong!!! Temps at 1.5 mtrs are fairly constant. Refrigerant in the exchanger boils at 0C. I watched the domestic hot water heating thismorning from 46C to 52C in less than 10 minutes.
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • geotherm wrote: »
    Wrong!!! Temps at 1.5 mtrs are fairly constant. Refrigerant in the exchanger boils at 0C. I watched the domestic hot water heating thismorning from 46C to 52C in less than 10 minutes.

    Nope,

    You are wrong. The environment cannot replace the heat at the same rate as it's extracted. Note that I said it can be several years before it's noticed.

    There is an actual example somewhere of a village that's been run off a gshp for several years and the efficiency is now dropping off substantially.
    Happiness, is a Kebab called Doner.....:heart2::heart2:
  • edited 21 January 2011 at 12:11PM
    lovesgshplovesgshp Forumite
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    edited 21 January 2011 at 12:11PM
    thechippy wrote: »
    Nope,

    You are wrong. The environment cannot replace the heat at the same rate as it's extracted. Note that I said it can be several years before it's noticed.

    There is an actual example somewhere of a village that's been run off a gshp for several years and the efficiency is now dropping off substantially.
    Thanks Chippy. Sorry for the long delay in answering, but the thread has only just been reinstated. Do you have any info or articles about this village, as would be interesting reading.
    I monitor my pump here and have not seen any performance reduction over the last 5 years. If you take the basis that in winter, a heat pump is running circa 10 hours per day, with a flow rate on a ground loop of 11 ltrs per minute (for a 11Kw output unit) , then the recharge time is longer for the loop. At the moment, I am getting 6.0C in with 2.0c out Outside temp 2.0C and snowing today). As the heating need is reduced in say Spring, this then starts to rise and during the summer we get even higher inlet temperatures. Some people use the ground loops to slightly cool the house, as passive cooling in the Summer months, when outside temperatures are higher than the feed in temperature
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • edited 21 January 2011 at 12:25PM
    markumsmarkums Forumite
    47 posts
    edited 21 January 2011 at 12:25PM
    (reply to post 23)

    So the advice would then be to add 50% or 100% to the recommended size of the ground loop?
    I've always wondered about how different the 'cooling factor' of a pump would really be in wet ground and dry ground. I would imagine the wetter ground being better for pumps due to how easily the heat is transferred and the moving water table being refreshed constantly and gradually over months/years.
    Or am I just being a bit thick...
  • lovesgshplovesgshp Forumite
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    markums wrote: »
    (reply to post 23)

    So the advice would then be to add 50% or 100% to the recommended size of the ground loop?
    I've always wondered about how different the 'cooling factor' of a pump would really be in wet ground and dry ground. I would imagine the wetter ground being better for pumps due to how easily the heat is transferred and the moving water table being refreshed constantly and gradually over months/years.
    Or am I just being a bit thick...
    To increase the length of the ground loop would only incur far much extra cost. You only get about .25C per extra 10 mtrs. A recent installation had 2x11kw pumps, with 2 x 162 mtr excavations so nearly 650mtrs of available heat input, 3 mtrs apart carrying 2 input/outputs in each. House size 360 sq mtrs using radiators.
    Yes, wet soil is far better at holding heat than sand, and any installation company should take those facts into account when designing a system.
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • CardewCardew Forumite
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    geotherm wrote: »
    House size 360 sq mtrs using radiators.

    360 sq metres - all heated? That is a BIG property.
  • Have you come across many people doing their own digging and backfilling of trenches? Does it need to be done by people who have full licenses to comply with installation standards or anything?
    I ask as i've done alot of digging and plant work myself before and thought when i get around to it, this could be a massive saving for me.
  • lovesgshplovesgshp Forumite
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    Cardew wrote: »
    360 sq metres - all heated? That is a BIG property.
    Hi Cardew.
    Many of the properties here are old farmhouses that have been restored. The one above is in Tuscany. The norms are around 200+ sq mtrs. Local to myself there are 2 houses 240 sq mtrs using 14Kw pumps, 260 and 300 sq mtr using 17Kw output units
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • edited 22 January 2011 at 6:13PM
    lovesgshplovesgshp Forumite
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    edited 22 January 2011 at 6:13PM
    markums wrote: »
    Have you come across many people doing their own digging and backfilling of trenches? Does it need to be done by people who have full licenses to comply with installation standards or anything?
    I ask as i've done alot of digging and plant work myself before and thought when i get around to it, this could be a massive saving for me.
    The way that we install here is as follows: Once we get all the technical detail of the property and size the pump, then we mark out the excavation lines. The normal depth is 1.2-1.5 mtrs. If 2 excavations they should be mimimum 3 mtrs apart and 1.2 mtrs wide. A local excavation company will normally do this and then an engineer will arrive for supervising the loop layout and pressure testing before the backfill. Depending on the soil type, sand may be required under and over the loops.
    The ground loop collectors ( which must be accessible ) should be at a maximum distance from the house of 40 mtrs and at a depth of 60 cms with the lines insulated and from them to the house/heat pump.
    There is no reason why you could not complete the excavations yourself.
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • weldawelda Forumite
    600 posts
    Why was the thread pulled, then re-instated?
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