 | Home > Off Topic > Air source heating. Any feedback? |
 
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373  
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Not air source but we had a ground source heat pump put in 3 or 4 years back.
Bit of a no brainer if you're on oil and the costs are much more predictable rather than swinging between 20p and 75p a litre! I work in Energy so if you wanted me to validated the sales guys numbers drop me a PM. Any savings costs will be relative to the price of oil at the time. £600 a year sounds optimistic, especially for air source. Ground source is a bit more efficient and we roughly break even on the electricity costs vs the oil costs. |
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4th Jan 2021 4:15pm |
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| Rosco Member Since: 03 Dec 2010 Location: Burntwood Posts: 1833 
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Working for a house builder, this is something we are starting to look into, and in early talks with manufacturers as we're going to have to change from gas boilers at some point.
I dont know how large your property is, nor its make up, but one manufacturer is spec'ing 6kW systems for our 4 bed property which is 1260 sq/ft, so unless your property is either really really palatial or you still have a bit of hessian sack instead of glass I suspect 17kW is a tad overkill 2007 - Stornoway Grey 90 XS SW - Gone 2002 - Black Discovery II - Gone 2014 - Montalcino Red 110 XS SW |
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4th Jan 2021 4:23pm |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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You also need to be aware that air or ground heat pump don't work very efficiently at producing hot water at the same temp as an oil system. Oil will happily pump out 65c for your heating, heat pumps won't and will be happier at 30-45c. You will therefore need to leave it running for longer to maintain temperature and may also need to look at either upgrading your radiators or installing underfloor.
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4th Jan 2021 4:32pm |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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Given that the thermal requirements part of the calculation is capped at 20,000 kwh, it sounds like they have used an efficiency rating for the heat pump of > 450% to come anywhere near the quoted £12,000 total payback figure. 250% is more normal for a air source and would lead to a total payback figure more like £9000.
I'd check with them before you commit how they've arrived at £12k. There's a fairly straightforward page on the RHI website to give you an indication as to payback: https://renewable-heat-calculator.service....ation.aspx |
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4th Jan 2021 4:42pm |
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| Rashers Member Since: 21 Jun 2015 Location: Norfolk Posts: 3508 
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Mitsubishi Electric (I have no connection) now have an air source heat pump which will produce 'normal temperature' hot water. The other systems will tend to rely on immersion heaters. (These are also used to pasteurise the water cylinder to prevent Legionellas disease and will be set on a timer). As Rosco says, this is the way that house building will be going as for years we have looked at electricity as being expensive, uncontrollable and reasonably inefficient, heat pumps are looked at as being environmentally acceptable due to the de-carbonisation of the electricity grid. Be warned. Your existing radiators may not be as efficient (or large enough) to emit the same amount of heat as from an oil or gas boiler. This is one of the reasons that these are not universally seen as a standard upgrade to oil/gas boilers. In a new installation, this will have been allowed for and part of the design. ASHP are best used on underfloor heating, but its not impossible to use on LTHW radiators. A couple of down sides. If you are looking at insuring your heating system against breakdown via your home insurance, this can be a bit of a problem. I am not sure whether this is due to the companies not being on board with the 'new' tech or, which is the second downside, they are nearly always a throw away unit. If it goes wrong, they can be horrendously expensive. They are not built like normal Air Conditioning units. I have spoken to a couple of Air Conditioning companies who don't touch domestic ASHPs due to costs involved in repair. One make of unit is 4 figures for a new control panel. An Engineer told me they serviced and repaired the units for housing associations but not individuals due to the inevitable bad taste in the mouth once the quote is delivered. You also need to be sure your incoming electrical supply is up to it. An old 60 Amp single phase supply will struggle on Christmas Day when all four rings of the hob, both ovens are on, and the ASHP is going hell for leather. Not impossible to upgrade, but something to think about. Don't let that put you off. This is the way domestic heating is going. Even in large blocks of flats. I would not trust the sales bloke as far as you can chuck him. I would try and get advice from a heating engineer who understands how heating systems work. It is all to do with the temperature of the water produced in the ASHP and your radiator pipework and sizes. Hope that helps. For what its worth, when my boiler breaks, this is what I will be looking at fitting. But I would look for independent verification rather than salesman. |
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4th Jan 2021 5:11pm |
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| lohr500 Member Since: 14 Sep 2014 Location: Skipton Posts: 1317 
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Thanks for the feedback so far.
Agree camelman. Some predictability on electricity pricing is preferable to the headache of trying to second guess the oil price movement and when best to fill up the tank. Thanks for the offer of validating the numbers. I'm expecting more detail next week after they have been back on Wednesday to do a more detailed survey. Today the engineer just measured the room and existing radiator sizes, looked at our historic oil and electricity consumption, heating usage, building construction and the loft insulation and double glazing. Even if we only broke even on running costs, then I still think it is a no brainer because of the fact that the old boiler is going to suffer a major failure at some point soon. Hopefully though, because the old system is so ancient and inefficient, there could be some saving to be had on running costs. He did explain that it would run at a lower temperature and that some of the radiators would need upgrading which was included in the original estimated cost. He also indicated that it would need to run longer in order to reach and maintain a 22 deg internal temp and that the way I was running our existing boiler was not very efficient anyway. (Running through winter in the evenings only, so allowing the house to cool right back down through the day). I am keen to see the detailed consumption numbers with an assumption that the system will run most of the time through the winter to maintain 22 deg, perhaps with some overnight fall back. At the end of the day, I know how exactly much oil we have used over many years and approx. how much electricity we are using for the immersion heater. So I will be able to compare our existing costs with part time heat, to his air source solution running for longer. Thanks also for the heads up on the payback. The spec for the Grant unit he is suggesting is this : https://www.grantuk.com/media/3418/hpid17r...he-v15.pdf Do any of the COP numbers on the data sheet suggest that at 20,000kwH capped, it could payback £12k. I'm not sure how it works. If they can't lock in the grant at close to the £12k initially suggested, then it starts to look less attractive, unless they shave cost off the installation. Sadly not palatial Rosco, but an old converted farmhouse with extension, running to 2800sq/ft in total. We did replace the sacks with glass a few years ago, but it's still a big old shed to warm up. A total of 19 radiators across three levels 
Probably not a direct comparison but the old oil boiler is rated at 23kW/80,000 BTU input with the current burner nozzle and a published efficiency of 70% |
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4th Jan 2021 5:15pm |
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| Rashers Member Since: 21 Jun 2015 Location: Norfolk Posts: 3508
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Something else I failed to point out. New houses, love them or hate them, are incredibly well insulated and should have very little air permeability or leakage so on a new build, the ASHP can be sized accordingly. The new house will not need as much energy to heat it as an older built one. This is another factor which needs to be thought out when retro-fitting any new heating system.
I am not a heating engineer. I'm sure there are a couple of Members on here. Might be worth PM'ing Joe the Plumber to see what his take is on them? |
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4th Jan 2021 5:18pm |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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^^^^^ HI Rashers, the 65c quote was in relation to the central heating water temperature.
The hot water temperature (at the taps) was one of our initial concerns but the system happily produces 48c which is more than enough. The immersion units tend to only be used when the legionaires cycle is required once a week for a couple of hours to get the temperature in the system really high. The higher you crank the central heating water temperature up, the more the efficiency drops off. Both air and ground pumps work best producing lower temperature constant heat output (at say 30c) which is why they need bigger rads or ideally underfloor. We managed to keep our existing rads as they weren't that old but have the heat pump set to around 45c for the heating circuit. As you say, they are the way forward, for every kW of electricity our ground source uses, it produces almost 4kW of heat  |
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4th Jan 2021 5:27pm |
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| lohr500 Member Since: 14 Sep 2014 Location: Skipton Posts: 1317
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Hi Rashers,
The technology does worry me. Our old boiler is now 30 years old and it has cost me nothing in terms of service engineer call outs. I have serviced it myself for the past 25 years. Much like an old Land Rover it is simple to maintain with a few spanners and a screwdriver. Other than regular nozzle and filter changes, I've had to replace the blower fan motor, ignition control module and a few other bits and pieces over the years. But as and when the main jacket fails, it will be past the point of no return
That being said, the new unit and control systems would be covered as part of the installation plan for the 1st 7 years and with an option to extend the warranty after that. Again I need to see the details once they submit the full proposal. He looked at the incoming electrical supply today and said it was a 100 Amp supply, but that the total loading consideration would also be looked at during the detailed survey on Wednesday. We already have a 30 Amp Electric Aga hooked up which mainly recharges overnight on Economy 7, but which can kick in during the day if the core temperature drops too low. So that's already eating away at the available current!! No hob as the Aga takes care of that and no electric showers. The guy who came round was an installation engineer and not some well heeled suited and booted sales person. But yes, I will still get a second opinion before making any decision. Company is called Renewafuel and they seem to get good overall feedback on Trustpilot and other sites. It looks as though they sub out the actual work though to other installers. |
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4th Jan 2021 5:41pm |
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| Rashers Member Since: 21 Jun 2015 Location: Norfolk Posts: 3508
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Absolutely, camelman
The hot water temperature issue becomes a problem if you have badly insulated pipes or long runs. I work in the building services industry and it is quite amazing how the electric heating has gone sinner to saint in only three or four years. I am afraid I have become very cynical about Sales persons over the years. I can count on one hand those which I trust. Those that turn a job down because their solution is not the right one for your problem. The one's that will tell you that they won't be able to make a delivery date. These are the people that I turn to time and time again. Not the one's which promise the world, then won't answer their phones when it all goes belly up. We have had quite a few 'green' alternatives to oil and gas boilers. Combined heat and power units (which were mostly gas powered) where the boiler would also generate electricity, thermal solar panels, biofuel boilers. All of these now seem to have lost favour, but were seen as the next new thing. As things stand at present, air source heat pumps are the way forward in the foreseeable future. There is talk of using the gas supply network for hydrogen supplies for domestic boilers. In the short term mixing 20% Hydrogen in with the natural gas. What the golden ticket would be is enough solar PV Panels to power your ASHP during the hours of daylight and perhaps an excess to charge up a battery storage unit to save the surplus for night use |
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4th Jan 2021 5:49pm |
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| stew 46 Member Since: 26 Jan 2012 Location: Wadebridge ,cornwall . Posts: 561  
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I’ve build and converted a few property’s over the years for customers, this first picture I help design and was the main contractor around 9 years ago , it has large air source and Pv panels, underfloor heating on all 3 floors , I think it’s around 400 sm and all still working perfect
 Click image to enlarge Click image to enlarge And this is another we are working on at the moment Click image to enlarge Click image to enlarge And this week we have started another barn conversion that will have air source and full underfloor heating etc
I would defo have air source if I had time to build my own place |
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4th Jan 2021 5:49pm |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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Make sure the 7 year maintenance deal is 'watertight'. One of the biggest players in this area (ICE Energy) folded a couple of years back leaving lots of people with no cover, having payed the maintenance fees in advance.
We did have an issue with ours 2 years in and the pump needed to be rebuilt, (with £2k of parts alone). We also had to inform the distribution company due to the increased load on the supply but that should be part of the installers standard procedures as part of the installation. |
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4th Jan 2021 5:54pm |
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| Andy T Member Since: 25 Aug 2017 Location: Bucks Posts: 230 
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It's a Mitsubishi one and no issues with it at all
Once a week it does a 65degree 'anti Legionella' cycle but otherwise from memory our water's set to around 50degrees. At installation we did have a new hot water cylinder and a couple of our radiators were upgraded to bigger ones. I'd have gone for ground source through choice, but it was too impractical where we are The RHI isn't as generous as for our solar panels but the incentives mean that we're still being paid to heat/light and cook with an electric aga! Happy to chat if you want - PM me your number if so Good luck with your decision Cheers Andy 2011 2.4 White 110 CSW LHD 1998 300TDi Wolf TUM 2015 2.2 Corris Grey 90 2009 2.4 Alaska White 110 Commercial - gone 2006 TD5 Barolo Black 90 - gone 1995 TD5 Green 90 - gone 1984 2.25 Marine Blue 88 |
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4th Jan 2021 5:55pm |
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| Rashers Member Since: 21 Jun 2015 Location: Norfolk Posts: 3508
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Air Source / Underfloor is a no brainer as you use the mass of the building (the concrete floor) as a large storage heater. If I built a house, this is what I would do (I would also go for ground source heating, but you need either a very expensive drill or a fair amount of land for that)
lohr500, if the company you are dealing with is going to sub the work out, it may be worth trying to find a local supplier to where you live for a price? Do you know the manufacturer of the external air source heat pump? |
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4th Jan 2021 5:56pm |
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