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Heating and cooling: air source heat pump - but which one?

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  1.  
    • CommentAuthorgreenpc
    • CommentTimeMar 5th 2008 edited
     
    hi,

    we're building in the scottish borders, small plot, well insulated house and have essentially decided on using an air source heat pump for heating (ufh) and dhw.

    big players up here seem to be the respective sales agents for nibe (fighter) and thermia (atria) heat pumps, with little to choose in terms of COP, size of pump or even cost - 6-7K after grant.

    anybody got good or bad experiences of these respective heat pumps? I have little doubt these are quality products up to the job, but I am also aware there are many other players coming onto the market, and difficult to escape the notion that the generous scottish renewable grant of 33% simply inflates prices by around 33%...
  2.  
    See

    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1354&page=1#Item_4

    and my offer/contact details there. Our experience is with GS rather than AS, though. Nick
    • CommentAuthorgreenpc
    • CommentTimeMar 7th 2008
     
    thanks for this. peter.
    •  
      CommentAuthorScanheat
    • CommentTimeApr 11th 2008
     
    Grants or not...
    There are good, cost effective Air to Water Heat Pumps available for about half of the cost you mentioned. Due to the strict rules of the forum I'm not sure I can mention the product names though. Very frustrating. Yes, our experience about the grants is the same, when they are available, the prices are quickly inflated at least to the value of the grant. This is especially the case with local council run projects and has a very negative effect on any future green development. As an example, here in Cornwall there was a GSHP project at a local school. The pump cost was £22500,- and digging the trench £36000,- ! Then they made a study to assess the energy saving and cost effectivness of the project. Surprise, they concluded that there were no savings at all when using the Heat Pump in the project. Naturally this will put the same council off for any future similar development. In this case, the price was inflated at least 60%. Therefore my advise for everyone is to look at the final price of the project rather than the possible grants available.
    • CommentAuthororkenny
    • CommentTimeApr 15th 2008
     
    Hi all I have just joined this forum and am in the same boat as greenpc.
    I am building a timber frame kit house in the North of Scotland and am planning to have an ASHP for ground floor U/F heating, DHW and 2 radiators on first floor. I have looked at the brands mentioned by greenpc and they look good. However a certain manufacturer famous for boilers now makes one which is very competitively priced. There are also units for sale on a certain internet auction that offer units in the same price bracket.
    Is it simply you get what you pay for? I dare say it is but at the end of the day these are working like a fridge but backwards and how often does a fridge break down!?
    I am also having a wood burning stove, would a back boiler be a good idea? I had originally wanted an ASHP to work alongside a Megaflo cylinder but some of the ASHP manufacturers have their own cylinders. Plus I don't think a back boiler can work with a Megaflo.
    Does anyone have input or experience of any of this? I would be very grateful to hear of any.
    • CommentAuthorDavid R
    • CommentTimeApr 16th 2008
     
    There's quite a wide choice of ASHP, so I'd hope that there'd be some price competition. It seems that the equipment cost of a good quality unit (5 or 8 kW) without hot water storage is £3-4k. 'Good quality' should mean a fairly quiet compressor driven off an inverter to allow a modulating output.

    For example:
    Daikin Altherma - good COP, range of sizes, split system.
    Mitsubishi Ecodan - a packaged external unit, so only needs a plumber to fix; currently 8kW, with 5kW to come in September
    Hitachi Aquafree - good COP, bit noisy

    Worcester Bosch are about to launch a product, and I've heard that Toshiba will bring one out this year.
    • CommentAuthororkenny
    • CommentTimeMay 12th 2008
     
    Hello again,
    I am now considering having an ASHP running alongside an electric boiler. The ASHP will be the primary heating source and the boiler will work as a back up when necessary. I can have a 12kw ASHP but only run it around 75-80% to keep the efficiency high. I then plan to use a Megaflo for hot water storage.
    Any thoughts anyone?
    • CommentAuthorgreenpc
    • CommentTimeJul 9th 2008
     
    hi all,

    just updating - we have settled on the nibe system. no doubt can get (a bit) cheaper systems, which probably just as good. convenience, reliability and local availability of spare parts/expertise as much factors in our decision as cost. I am told nibe stuff v. solidly built. orkenny - the nibe (and many others looked at) system is ashp with integrated hot water cylinder/electric boiler, so no need for separate dhw storage. can update you at xmas time when house built and ashp installed and tell if you this is actually what it is and whether it works! lot of misinformation around on ashp's when you google it on british/irish forums (not greenbuildingforum). I don't think its the be all and end all of heating systems, but interesting that they use it v successfully in much colder places in the world and yet many folk in this country remain so sceptical...! -reminds me of the wearisome debate regarding timber frame vs brick/block built...
    • CommentAuthorSimonH
    • CommentTimeJul 9th 2008
     
    <blockquote><cite>Posted By: David R</cite>'Good quality' should mean a fairly quiet compressor</blockquote>

    My advice would be so make sure you've definetely heard one running at full pelt.

    My only experience of ASHP is on hols in america, where they have been fitted to villas or apartments I've stayed in. To use the work "noisy" would be an understatement! The best way I can describe the "character" i.e. frequency and pattern of the noise is that of a mains electric power drill when you have it on crawl speed, but it's as loud as the drill at full speed. Easily preventing sleep.

    I'm not saying all ASHPs are like this, but I'd want to hear one running before I spent my money!

    Simon.
  10.  
    Hi,
    I'm new to this site and have been trying to find out about ASHP and whether they actually save any CO2 compared to a gas boiler. I've read lots of the posts and am still confused. Does anyone actally have one running and can let me know how much electricity it uses?
    Gill
    • CommentAuthorboo0302
    • CommentTimeAug 4th 2008
     
    <blockquote><cite>Posted By: greenish gill</cite>Hi,
    I'm new to this site and have been trying to find out about ASHP and whether they actually save any CO2 compared to a gas boiler. I've read lots of the posts and am still confused. Does anyone actally have one running and can let me know how much electricity it uses?
    Gill</blockquote>
    • CommentAuthorbimmaboy
    • CommentTimeAug 5th 2008
     
    <blockquote><cite>Posted By: boo0302</cite><blockquote><cite>Posted By: greenish gill</cite>Hi,
    I'm new to this site and have been trying to find out about ASHP and whether they actually save any CO2 compared to a gas boiler. I've read lots of the posts and am still confused. Does anyone actally have one running and can let me know how much electricity it uses?
    Gill</blockquote></blockquote>

    Depends on your property you need a sap/sbem to be done, just got one for a property and was given

    Saving 4.1 Tons per year against gas boiler

    Saving 9.9 Tons per year against oil boiler

    Saving 12.6 Tons per year against electric boiler
    • CommentAuthorsinnerboy
    • CommentTimeSep 30th 2008
     
    As far as i know the most comprehensive European lab testing of heat pumps can be found here , in ( Swtizerland )

    http://www.ntb.ch/3896.html

    They test about 25 units annually - manufacturers volunteer units for testing

    So I would down load the reports and see how the model you are considering ranks in performance
    • CommentAuthorsinnerboy
    • CommentTimeSep 30th 2008
     
    This report ( sorry in German language - I don't speak the language - a German workmate translated "the gist "of it for me )

    http://www.agenda-energie-lahr.de/WP_Jahresbericht2006-07.html

    is a result of - admittedly limited - field tests carried out by a not for profit society concerned with energy efficiency / CO2 emmisions . more about them here

    http://www.agenda-energie-lahr.de/index.html

    please turn to page 14 of the report

    luft - warmep mean air to water
    erd warmep means ground source heat pump

    the grey area to the left are the results of agenda-energie-lahr findings . the other columns are published figures of other bodies

    figures like 2.8 , 2.3 , 2.65 etc are the COP's
    figures below in brackets indicate the number of heat pumps field tested

    a loose translation of the text above the test results is " why should a consumer pay €7k more for an air to water heat pump , which will produce more CO2 and be less energy efficient than an highly efficient gas boiler . with this technology we ( Germany ) can not meet our energy reduction targets untill 2020"

    Now quite honestly I can't really put this report into it's proper context - un settling on the face it though
    • CommentAuthorpcworld
    • CommentTimeOct 8th 2008
     
    Hi All,

    Just found a Link that may answer some of your questions

    http://www.nottenergy.com/energy-costs-comparison3

    I can't agree with the CO2 re ASHP & GSHP, sine at the stated efficiencies, relative to the Electricity Tariff used, I arrive at better figures.

    Also worth noting:

    ASHP remains efficient at temperatures down to 2degC and continues to operate to well below freezing. When related to the number of days per year that outside Air Temperatures fall below 2degC, an ASHP remains viable, even if it needs some help on the coldest, darkest Winter Night.

    Remember, planning the use of an alternative solution also involves planning to adapt to it's strengths and weaknesses. If you plan for the worst case, ie the coldest, darkest night, you will be planning to waste energy at most other times.

    I like to think of it in relative terms:

    I have a Gas Guzzler to tow my Caravan on Holiday. We have another car, a micro mini guzzler; which we use to run around in. By choosing what to use, when, we get the best of both worlds, ie. Economy and Comfort, if you get my drift.
    • CommentAuthorwookey
    • CommentTimeOct 8th 2008
     
    Bimmaboy, in principle, yes an ASHP should reduce CO2 emissions over a gas boiler. If you can get a COP of 4 then it is about 200% efficient including transmission and generating losses. The best you will ever get out of a gas boiler is around 100%, so Heat pump gives you twice as much energy. As your COP drops to currently-more-often-found numbers like 2.5, 3, then it should still be a bit more efficienct than gas, but for CO2 you have to figure in the carbon factor of your mains supply. If it's all coal then the gas boiler is better. If it's all gas then the heat pump wins. In practice it will be some mix of these and they probably work out much the same. In the medium-long term efficient heat-pumps plus lots of carbon-free power generation are probably the most efficient way of heating most houses.

    Thanx for those links sinnerboy - look like interesting reading for some real-world figures.

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