ASHP - How to know the actual COP?

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  • Yeah, note what you say about test-bed data.

    To be pedantic, haven't yet actually made any decision about an ASHP, but to answer your question, it was more a question of preferring UFH to hot air. I think it gives a more comfortable heat, and I find hot air gives a stuffy sort of heat. Just my preference, and I realise that might not be the ideal choice if you are looking at it purely from a financial point of view.

    On another front, anyone know whether there are any significant technical differences between a swimming pool heat pump and one that is designed for house space heating?

    There is certainly quite a difference in price.....
  • Cardew
    Cardew Posts: 29,036 Forumite
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    Yeah, note what you say about test-bed data.

    To be pedantic, haven't yet actually made any decision about an ASHP, but to answer your question, it was more a question of preferring UFH to hot air. I think it gives a more comfortable heat, and I find hot air gives a stuffy sort of heat. Just my preference, and I realise that might not be the ideal choice if you are looking at it purely from a financial point of view.

    On another front, anyone know whether there are any significant technical differences between a swimming pool heat pump and one that is designed for house space heating?

    There is certainly quite a difference in price.....

    Swimming pool heat pumps are a well developed technology and of course ideally suited to raising large quantities of water just a few degrees with no requirement(usually) to have the water above 30C, and they are operating in high ambient temperatures.

    I was put in charge(as a resident) of a project to heat a large communal pool in the USA. There are some really excellent US Government websites that deal with all forms of pool heating - which I unashamedly quoted.

    Depending on the size of your pool, you might find the cost of the heavy duty electrical cabling and supply frightening - these things use serious power!

    Also noise can be a problem on these big heat pumps.
  • lovesgshp
    lovesgshp Posts: 1,413 Forumite
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    Cretanrunner.
    I tried to see if the manufacturer of the heat pumps we use here in Italy has an agent near to you, but there were none, so unfortunately cannot help on that.
    Re pool heating, you should be able to get a pool control unit to work in conjunction to a ASHP/GSHP. I have a client who uses one and is very happy with it.
    His comment after the startup: (30th May 2011)
    The heating raised the pool temperature from 25 degrees to 28 overnight, and is just what was wanted.
    I cannot post the PDF file of the control unit, but if you send a PM with your email address, quite happy to do so.
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • Cardew wrote: »
    Depending on the size of your pool, you might find the cost of the heavy duty electrical cabling and supply frightening - these things use serious power!

    Also noise can be a problem on these big heat pumps.

    Cardew, thanks for the pointers re pool heat pumps. Understood, except for the bit about electrical supply. We are on 3 phase, total supply load around 150 amps. Could you elaborate at all?
  • In case it gets lost, any views on my earlier question about sending the hot water to a thermal store rather than direct to the UFH?
  • Cardew
    Cardew Posts: 29,036 Forumite
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    Cardew, thanks for the pointers re pool heat pumps. Understood, except for the bit about electrical supply. We are on 3 phase, total supply load around 150 amps. Could you elaborate at all?

    That supply will cope with the demands of any swimming pool heat pump.

    It is the cost of running heavy duty wiring to heat pump location, contact breakers etc that can be expensive.
  • lovesgshp
    lovesgshp Posts: 1,413 Forumite
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    Email sent, let me know if it is ok. Yes you can connect to a thermal store. This link may be of help. It's a guy who deals with heating solutions in Italy.

    http://heatingitaly.com/default.aspx
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • albyota
    albyota Posts: 1,106 Forumite
    In case it gets lost, any views on my earlier question about sending the hot water to a thermal store rather than direct to the UFH?

    A 1500 L thermal store is massive, I would advise just using the heat pump connected directly to the UFH, main reason is with Inverter driven kit, when you only need a little heating, a heat pump will provide just the right ammount and have a faster response, as opposed to trying to heat up at least 1200 litres (will take ages) to raise the store temperature high enough (35) for the UFH, I would also advise using a 300 Litre DHW cylinder with 3m2 surface area coil, I would not in any circumstances use the thermal store.

    Yes the COP's quoted in my previous post is from Mitsubishi Electric technical department and are not published anywhere, until now :eek: but I have an Ecodan and have run my own trials and can confirm they are as good as spot on.

    I would not advise using a swimming pool heat pump to heat your house.....to all intents and purposes....it will work.....but you will be replacing it next year when its F**k'd.

    AL
    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!
  • grahamc2003
    grahamc2003 Posts: 1,771 Forumite
    jeepjunkie wrote: »
    That'll will be me then... ;) Wouldn't say my expenditure was massive, not much more than complete new oil install as we were starting from scratch...

    Winter running costs... any fuel would be expensive heating this big old place. I'll just do one days OT and that should cover the winter quarter :D

    You've been watching to many episodes of cowboy builders... There are loads of highly skilled heating engineers that pride themselves on doing a good job.

    Perhaps former DG salesmen doing ASHPs is an English thing ;)

    Not sure how even the best builders can stop water condensing or ice being deposited on cold surfaces. Do you understand that is the problem, even when installed perfectly?

    You have a coil at probably -30c with air being blown over it. The water in the air will simply form water (which will then freeze) or ice directly onto the coil under UK winter conditions. How you get rid of that ice efficiently is a technically difficult thing to do, and even more technically challenging is the unit knowing when the ice has been fully cleared. If the ice isn't cleared fully, and the unit switches out of defrost mode, then the ice will be cooled much further, with the heat pump sucking the heat out of the ice instead of the air, causing even more ice deposition - and it could go on until the whole outside unit is a big block of ice - there have been pictures on mse of this.

    Obvioulsy you'd expect makes like Mitsui to have defrost strategies which wouldn't allow that to happen. But of course any defrost strategy is a compromise - the more certain you are to clear all the ice, the more energy used in doing so.

    As well as the cop reducing as the ambient temperature reduces (due in part to less heat in freezing air being available than from air at higher temps), there is the added problem of defrosting when the ambient drops, depending on the relative humidity, or rain or snow. The cop of course is negative during defrost, but cops quoted from manufacturers are quoted under steady state operation in the lab (i.e. not taking into account defrosting).

    It's quite possible many other countries don't suffer any ice on the outside unit due to different weather conditions.

    So whether or not anyone gets problems from poor installation, you're almost certainly going to get icing on your outside unit (if you're in the UK), and whether that is a problem depends on the defrost strategy and whther the range over which the strategy is designed is breached or not (i.e. it's likely I suppose that last winter the ambient temperatures were below the design criteria of many heat pumps).
  • Cardew
    Cardew Posts: 29,036 Forumite
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    jeepjunkie wrote: »
    Anyway I've said all this before and only answered as Cardew is scaremongering again having latched onto that EST report... ;)

    As I understand it you got an ASHP fitted this Spring(paying £14,000?) and all over MSE you are singing the praises of ASHPs without having gone through a winter.

    Why should the EST report not be brought to everyone's attention? This is one of the only trials that give the results showing performance of 29 systems over a 12 month period with the information presented such that a reasonably intelligent layman can understand.

    By any standard the results were poor - and the trial has been extended to try and see if lessons can be learnt for the poor performance of many systems.

    There are also many reports on MSE and all over the web of systems that are dreadful. Unable to maintain temperature in the house and costing the earth. Several on MSE have resorted to ripping out the system.

    The current situation is that people are taking pot luck if their ASHP system will operate correctly and no comeback if it doesn't work.

    Can you see many salesmen telling prospective customers that their house is unsuitable for an ASHP?

    EDIT
    I note you have deleted your subsequent post to which this post refers.
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