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  • FIRST POST
    samtheman1k
    Air Source Heat Pumps
    • #1
    • 24th Jan 08, 10:11 AM
    Air Source Heat Pumps 24th Jan 08 at 10:11 AM
    We recently moved into a house where, due to various issues, we were unable to get gas installed in our house and we also hated our storage heaters, like many others that I have read about on here. Last year, I installed an Air Source Heat Pump based system to provide ourselves with central heating and hot water and have written a description here in the hope that it may be of use to someone!

    The system that I opted for was the Mitsubishi Heat Pump Boiler combined with a Boilermate HP that is sold as a package and are designed to work together as the Boilermate controls the HP and is fully modulating. I went for this system primarily due to ease of installation as the output from the heat pump is hot water that can be fed directly into your central heating, rather than having to deal with seperate inverters and refridgeration engineers! This system can be installed by any competent plumber. The Boilermate is an unvented cylinder that provides mains pressure hot water to the entire house and is heated by the HP (and boosted to 60degC via a 3kW immersion heater if required to meet regulations).

    The first question I often get asked is 'what about the water temperature'?. Well, the temperature from the heat pump comes out at about 50-60deg C during normal use (according to the Boilermate sensors). The Boilermate HP actually has a 3kW inline electric heater to give the water a boost in temperature if required, but I don't think it is using this at the moment, and only will when the temperature drops outside. The boilermate has an external thermoneter to adjust the temperature of the water, but I have found that produces water that is too cold, so I have removed this to ensure that the water temperature stays at the maximum and then regulate the house temperature via a thermostat and TRVs. The following shows the output temperature of the heat pump verses outside temperature:



    So you can see that you'd only really need to use the electric boost if the outside temperatures drop below about -10/-15degC, which is rare for where I live in the South East, if you base your radiator sizes on a water temperature of 50-60degC. In fact, looking at that graph, I think I'm losing too much heat through the pipe between the boilermate and the heat pump, but I haven't finished insulating them yet (make sure you have good stuff (~!!!163;5/2m), not the normal stuff and keep the outside pipework as short as possible). ryansairconditioning.com (iirc) is where I got my stuff from.

    I'm not sure exactly how to convert the output temperature to a COP figure, but the HP maximum power consumption is about 2.1kW, so I'm sure someone can work it out! So I am effectively heating my entire 3 bed semi using upto 2.1kW of electric power (or 5kW in the worst case scenerio). I've posted the specs of the HP at the end of this pump for anyone who's interested.

    In terms of radiator sizes, Gledhill recommend that you oversize the radiators by 20!!!37;. However, we were a bit cautious in this and actually when for a 50% increase in our living room by swapping a single skin for a double skin one, and went for a 100% increase in the main bedroom as we like to be toasty! We did this by have two single skin radiators (due to the layout of the room). Our kitchen has a plinth heater that is rated at 100% extra IIRC, but it is a fan assisted one so is the same size as a lower rated one. We are installing underfloor heating in the bathroom too with a heated towel rail.

    In terms of cost, it's not cheap upfront. The boilermate and heat pump cost just over !!!163;4K to purchase. Then you have to add on the cost of installing the radiators and pipework (which I did myself) and you'll also need 10mm^2 cable running to the boilermate to provide the electric backup and 6mm^2 cable running to the heat pump outside (which of course all needs Part P certifying ) & also the commissioning of the system. We needed to upgrade our consumer unit too as we had a fuse box (with wires) rather than MCDs! Personally, I got a plumber to plumb in the actual boilermate as it is quite complicated! (although remember it just needs a normal plumber, not a specialist).

    I weighed the cost up against the cost of installing gas in our house, and as you have to pay the exact cost of gas installation (at c!!!163;2000 per day for the contractors, but less than !!!163;1k for a combi boiler), I think that the heat pump worked out cheaper as we'd have a very complicated gas installation due to access issues and the lay out of the land as the trench to the house would have to be dug out by hand!) and of course, there are many who don't even have the option of gas. Oil was another option, but is just as expensive to install and we didn't want a tank in our garden and oil isn't getting any cheaper! We couldn't get LPG as the tank wouldn't be in line of site to the road, so wouldn't meet regs.

    The main drawback is the noise generated by the HP itself. It is 49dB according to the specs, but I would say that it is about the same as a modern washing machine on spin cycle. This may or may not be a problem depending on where you live. The HP needs to be as close to your house as possible to prevent heat losses through your pipes, so you can't hide it at the back of your garden! However, it is hard to hear through a double glazed window, so shouldn't be too much of a problem. However, your neighbours may not be so sympathetic. There are no regs AFAIK on siting a HP as the main problem is the noise and that is already covered by the normal environmental noise regs. If you mounted it on your boundary next to your neighbours windows, then they may well complain. In Ireland, they are suggesting that there should be a 5m distance between any HP and a boundary, so we used that as a guide for England, but our garden is only about 7m wide, so doesn't actually quite meet that but we've done our best to site it in the least annoying place. We haven't had any complaints yet, but only time will tell. As mentioned, if it is a good few meters away, and your neighbours have double glazing, it shouldn't be a problem, although I'm not offering any guarantees! Also note that as it powers your central heating, it won't be running much during summer (bar hot water), so shouldn't be much of a problem when in the garden during the summer. Also, the HP is large. About 90cm by 90cm by 30cm, so you'd need a space to put something that size and is, tbh, rather unsightly! Although this is less than the size of an oil tank I suppose. It also needs a 30cm (iirc) space behind and 50cm infront for the flow of air, so can be mounted on bracket on the wall if you buy big brackets (it weighs about 90kg).

    In terms of running costs, we only installed it about a month ago, and the temerature has been between 0-10degC over the past month, bar a few sub zero days, and it seems to work out about !!!163;3 per day if it's on for most of the day, and about !!!163;2 per day when we are at work (on in morning/evening only). That is based on 8p/kwH and is the price for all our electric including cooking etc. We have cavity wall insulation, old double glazing (doesn't meet regs) and only 100mm of loft insulation so our house is fairly well insulated, but by no means well insulated.

    The key point I think is that in South east of the UK where I live, it rarely drops below freezing temperature anyway, so should be operating at a reasonable efficiency for most of the time. Obviously if we have an artic winter, then running costs will increase, but during summer, it will provide our hot water for virtually free (well, not quite as cheap as solar, but cheaper than gas anyway!).

    Finally, as the HP is running at greater than 100% efficiency most of time, my CO2 emissions should be less than all you gas boys, giving me a boost when we get a HIP done

    Any questions, then please ask and I'll do my best to answer!


    Info on the boilermate HP is here (under alternative energies);
    http://www.gledhill.net/water-storage/ws-index.htm
    and info on the HP is here:
    http://www.mitsubishi-aircon.co.uk/
    This is the spec sheet of the HP from the manual.
    Last edited by samtheman1k; 24-01-2008 at 11:09 AM.
Page 88
    • Cardew
    • By Cardew 22nd Feb 18, 10:45 PM
    • 27,332 Posts
    • 13,378 Thanks
    Cardew
    Living next to a canal would only be relevant if you were contemplating a Ground Source Heat Pump.

    It seems to me that you have read enough about ASHPs to know, or at least have serious doubts, that they will not meet your demands.
    • c13pep
    • By c13pep 26th Feb 18, 12:17 PM
    • 14 Posts
    • 6 Thanks
    c13pep
    Hi
    I have an ASHP feeding 20+ radiators and can categorically state that it works even with our target lounge temperature of 24 degrees. I have posted on here before that we operate the system as we did our previous Calor boiler ie. shut down between 10.00pm to 5.30am. My costs are acceptable for my large house and much in line with what I expected now that we are all electric.
    I fitted solar panels purely as a way of generating my own electric with the added bonus of a government payment every quarter.
    The one thing I learned early on is that these systems are especially suitable for underfloor heating where lower temperatures give out a more uniform heat but for us this was not an option.
    Our maintenance engineer recently told us of a latest development where flow temperatures are 60+ degrees but the system is still quite expensive.
    If you can`t get mains gas then I would have no hesitation in recommending ASHPs
    CHRIS
    • lovehols
    • By lovehols 26th Feb 18, 12:48 PM
    • 214 Posts
    • 122 Thanks
    lovehols
    Thanks Chris

    We are still researching options. We have read about Grants doing a hybrid system oil and ASHP but we have read so many mixed opinions.
    • c13pep
    • By c13pep 26th Feb 18, 1:07 PM
    • 14 Posts
    • 6 Thanks
    c13pep
    My own system was originally a hybrid system retaining the calor boiler for backup during very cold spells, however the second boiler has never been activated (outside temperature sensor kicks in at minus 5-8 degrees). As mentioned my system is shut down overnight when temperatures are at their lowest so it doesn`t operate when it would be at its least efficient. It does not take long for the system to warm the house thro`
    One thing I would do differently, in hindsight, would be the installation of solar hot water to give even more savings.
    If your installing underfloor heating then I would go for the ASHP as I can`t see any reason not to.
    PS my system is now 4 years old
    CHRIS
    • lovehols
    • By lovehols 26th Feb 18, 1:13 PM
    • 214 Posts
    • 122 Thanks
    lovehols
    My own system was originally a hybrid system retaining the calor boiler for backup during very cold spells, however the second boiler has never been activated (outside temperature sensor kicks in at minus 5-8 degrees). As mentioned my system is shut down overnight when temperatures are at their lowest so it doesn`t operate when it would be at its least efficient. It does not take long for the system to warm the house thro`
    One thing I would do differently, in hindsight, would be the installation of solar hot water to give even more savings.
    If your installing underfloor heating then I would go for the ASHP as I can`t see any reason not to.
    PS my system is now 4 years old
    CHRIS
    Originally posted by c13pep
    I guess one of my issues here is you say "the system is shut down when it would be at its least efficient". I guess that's my argument I want a system that is efficient when temperatures are low! For me that's when I want a toasty warm house and a nice steamy bath!!
    • matelodave
    • By matelodave 26th Feb 18, 1:39 PM
    • 3,542 Posts
    • 2,192 Thanks
    matelodave
    Your main problem with people's opinions is more often than not it's those who are dissatified who complain and criticise. There are probably many thousands more who are quite happy.

    As has been said, the main thing is to make sure that the system is designed as a whole by someone who understands what they are doing and for you to also understand how it works and to make sure that the whole system is specified correctly.

    Getting several quotes should produce similarly specified systems - if not then you should understand why and what the differences are.

    I prepared accurate information regarding temperatures required, room sizes together with wall, floor, roof and window construction info so they all had the same info to work from. I also did my own calculations to get a rough idea of what was required.

    I asked six companies to quote - two wanted a big lump of money up front, one didn't reply and three gave me a quotation, two based on Ecodan and one on Daikin or Ecodan.

    I visited two of the companies to see the equipment in operation and both of them visited my house as well. In the end I selected the Daikin solution with a PolyPipe overlay underfloor heating system as the quote was quite competitive and the company demonstrated significantly more knowledge. This was over seven years and eight winters ago and I'm extremely happy with it all.

    There's no problem with having steamy baths, you just have to accept that you might need to use an immersion heater to raise the water temperature to the higher level - using E7 would help with that.

    We are more than happy with our hot water at 45 degrees but if I want it hotter than 50 then the immersion heater will kick in (as it does every Saturday to sterilise the tank at 60 degrees). The extra 10 degrees on E7 wont cost much more as you've had the benefit of the heatpump efficiency to get it most of the way. You could also run it all night on E7 (or E10) if you so wish.

    Likewise you can have the house as hot as you like, you just need to ensure that the ASHP has enough capacity and that the radiators/heat emitters/underfloor heating is correctly sized to suit the flow temperature as well. The programmable stats turn it down to 17 degrees overnight and back up during the day.

    Each room has it's own programmable thermostat and the temperature is adjusted according to it's use - ie we dont have the bedrooms at 20 degrees all day, just for an hour or so in the mornings and at bedtime. We reduce it to 15 overnight as we cannot sleep in a hot room, likewise the bathroom only needs to be around 20 in the mornings and evenings and is set to 17 during the day. The study & lounge are set to 20 but the study goes down to 17 in the evening when it's not in use. Underfloor heating keeps all room toasty warm all over - no hot or cold spots and a real treat underfoot in the bathroom

    Most problems occur when the either the heatpump is undersized or the rads etc are too small to heat the rooms at the lower flow temperatures, usually because the heatpump has been bunged onto an existing system.

    You last comment indicates that you dont really understand how they work - we dont shut ours down overnight, just reduce the temperature. We cant sleep in a house that's much above 15-16 degrees, reducing the temperature a bit improves the system efficiency - even at 0 degrees outside, the system has a COP of over 2. With decent insulation the house may not need heating at all overnight.
    Last edited by matelodave; 26-02-2018 at 3:06 PM.
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    • lovehols
    • By lovehols 26th Feb 18, 1:54 PM
    • 214 Posts
    • 122 Thanks
    lovehols
    Thanks for that. You've given me a lot to think about. It's definitely one of my top priorities in the redesign and extension of the bungalow, it must be warm. I'm always cold!
    • c13pep
    • By c13pep 26th Feb 18, 6:34 PM
    • 14 Posts
    • 6 Thanks
    c13pep
    Your extension will be built to current building regulations, however these need to be considered as the minimum with regard to insulation etc. In the final analysis it will all come down to cost which climbs disproportionately the more you install heat retaining solutions.
    My ASHP was installed retrospectively on to an existing radiator system by a fully competent installation team consisting of plumbers, refrigeration/air con engineer and a fully trained Mitsubishi heat pump engineer. Even so the set up procedure took three months to perfect to our situation. I have to say that the technicalities of the system were really of no concern to me only the promise that it would work to my satisfaction.
    Your research will have shown that it`s the installation that counts with most of the current day equipment being fairly equal. All of the failures reported on the various forums are almost always down to poor setting up of the system and/or poor initial calculations.
    Good luck with your project
    CHRIS
    • richardc1983
    • By richardc1983 26th Feb 18, 7:37 PM
    • 1,918 Posts
    • 1,011 Thanks
    richardc1983
    Hi
    I have an ASHP feeding 20+ radiators and can categorically state that it works even with our target lounge temperature of 24 degrees. I have posted on here before that we operate the system as we did our previous Calor boiler ie. shut down between 10.00pm to 5.30am. My costs are acceptable for my large house and much in line with what I expected now that we are all electric.
    I fitted solar panels purely as a way of generating my own electric with the added bonus of a government payment every quarter.
    The one thing I learned early on is that these systems are especially suitable for underfloor heating where lower temperatures give out a more uniform heat but for us this was not an option.
    Our maintenance engineer recently told us of a latest development where flow temperatures are 60+ degrees but the system is still quite expensive.
    If you can`t get mains gas then I would have no hesitation in recommending ASHPs
    CHRIS
    Originally posted by c13pep
    When you say you shut it down do you mean a night set back to a lower temperature? You will likely find it saves more if it doesn't have to work as hard the next day to get back up to comfort temperature.
    If you found my post helpful, please remember to press the THANKS button! --->
    • Cardew
    • By Cardew 26th Feb 18, 7:50 PM
    • 27,332 Posts
    • 13,378 Thanks
    Cardew
    Your extension will be built to current building regulations, however these need to be considered as the minimum with regard to insulation etc. In the final analysis it will all come down to cost which climbs disproportionately the more you install heat retaining solutions.
    My ASHP was installed retrospectively on to an existing radiator system by a fully competent installation team consisting of plumbers, refrigeration/air con engineer and a fully trained Mitsubishi heat pump engineer. Even so the set up procedure took three months to perfect to our situation. I have to say that the technicalities of the system were really of no concern to me only the promise that it would work to my satisfaction.
    Your research will have shown that it`s the installation that counts with most of the current day equipment being fairly equal. All of the failures reported on the various forums are almost always down to poor setting up of the system and/or poor initial calculations.
    Good luck with your project
    CHRIS
    Originally posted by c13pep
    Agree completely.

    For such an expensive and complicated heating system Mitsubishi(for the Ecodan) should have their own factory installers and give the system their full guarantee of performance.
    • c13pep
    • By c13pep 26th Feb 18, 8:34 PM
    • 14 Posts
    • 6 Thanks
    c13pep
    Shut down is exactly that, system is switched off for night, which then makes my insulation etc. earn its keep. Even in weather like today (beast from the east) my house does retain its heat well.
    CHRIS
    • c13pep
    • By c13pep 8th Mar 18, 7:16 PM
    • 14 Posts
    • 6 Thanks
    c13pep
    For the benefit of clarity, whilst my lounge temperature is set to 24 degrees my hot water has a range of 42 - 52 degrees with the Mitsubishi hydrobox factory biased to maintain DHW temp before CH temp and I never use an immersion heater. The hot water provides steamy baths and is piping hot from early morning to late evening with the very efficient 300Ltr tank.
    If you read my earlier post properly then it says that `the system is shut down when it`s at its LEAST efficient. All ASHPs are less efficient in cold air, that`s just a fact, however less efficient is not that it doesn`t work it`s just that it has to work harder to maintain the temperatures, however my house holds its heat very well so I can afford to switch the heating off overnight.
    As has been mentioned many times on many forums it`s the total package that has to work .ie ASHP + internal system(radiators or underfloor etc.) + insulation and in particular whether the installation is retrospective as ours was.
    We are completely happy with our house and its running costs and I base my recommendations purely on that.
    CHRIS
    • richardc1983
    • By richardc1983 8th Mar 18, 7:51 PM
    • 1,918 Posts
    • 1,011 Thanks
    richardc1983
    Interesting post but if it holds the heat so well why don't you use a night set back? Just curious?
    If you found my post helpful, please remember to press the THANKS button! --->
    • zeupater
    • By zeupater 8th Mar 18, 9:30 PM
    • 4,144 Posts
    • 5,362 Thanks
    zeupater
    ... however my house holds its heat very well so I can afford to switch the heating off overnight ...
    Originally posted by c13pep
    Hi

    Our house is very similar ... plenty of insulation and loads of internal thermal mass to store the heat, meaning that heat-pump heating can be provided when most efficient operation is possible or the log burner not having to burn all day, or even every day ...

    The only problem with high mass buildings is that if you allow them to cool slowly, they take a load of energy to warm up again, in our case many hundreds of kWh, in which case it needs help from the GCH!! ... but once it's there it does last quite some time...

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
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