You might not need to change some of the radiators as it will depend on how warm you will want the room. We are in a 1930's semi only part insulated and it's almost no difference to the bills as we only have electric now and we get the government money so at the minute the cost to us to run it, is almost cost effective.
Air source heat pumps
- Thread starter Psycho Sonny
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Would you mind elaborating on your before and after setup whenever you have a chance? This is interesting to me.
I have an oldish and fairly large house at which i ripped the kerosene (oil) system out of (ancient and all needed replacing, 2500L tank was rusty etc), and replaced with an electric system boiler and megaflo. While i love this system (never runs out of oil and doesnt stink!), i fear that when i soon need to sell this house, that full electric will put people off as they will fear the bills. As such, i would like to replace the system boiler with an ASHP, especially with it being the latest buzzword, but i really have no appetite to change all of the new radiators or megaflo etc. I wonder just how much an ASHP would struggle with heating a "normal" system?
Jez, it entirely depends on what flow temperature your current system is designed for. The higher the flow temp, the smaller radiators you need and vice versa.
An ASHP will top out at 50C and preferred to be less, the lower the temp, the more efficient the system. A lot of boiler based systems are pushing 65C. The difference is significant.
If you have ‘oversized’ rads (for a typical boiler setup) or underfloor heating already then few changes will be needed on that front but in reality very few do.
Generally, an ASHP will fail to sufficiently heat a ‘normal’ set up with radiators design for high flow temps.
The only way you’ll know is to get someone in to do a survey and run the calculations.
An ASHP will top out at 50C and preferred to be less, the lower the temp, the more efficient the system. A lot of boiler based systems are pushing 65C. The difference is significant.
If you have ‘oversized’ rads (for a typical boiler setup) or underfloor heating already then few changes will be needed on that front but in reality very few do.
Generally, an ASHP will fail to sufficiently heat a ‘normal’ set up with radiators design for high flow temps.
The only way you’ll know is to get someone in to do a survey and run the calculations.
Thankyou for that @b0rn2sk8 - the radiators are not oversized at all, they are as close as we could get to the sizing of the inherited oil system. I have extended this system significantly into the newbuild areas of the house, with "normal" radiators. All UFH areas are separate with electric matting so not related to the wet system.
The electric boiler runs at a high temperature, the output is too hot to hold onto and the radiators become uncomfortable to hold a hand to. This is more of a marketing gimmick than anything else, to make people think that the otherwise very modern system (Nest controlled, megaflo, all new radiators, etc) is not an issue on a purchase. Perhaps i am being ott, at a recent valuation the agent seemed surprised and had a slightly odd face when i said that the system was electric. I fear the EPC result with it too.
As per your suggestion, I have an AC company coming to our new property soon (full conversion so central air heating/cooling), i'll extend their visit to this house too for a first hand opinion, as they install ASHP. Perhaps we can get a weak ASHP installed in tandem with the system boiler or similar...
The electric boiler runs at a high temperature, the output is too hot to hold onto and the radiators become uncomfortable to hold a hand to. This is more of a marketing gimmick than anything else, to make people think that the otherwise very modern system (Nest controlled, megaflo, all new radiators, etc) is not an issue on a purchase. Perhaps i am being ott, at a recent valuation the agent seemed surprised and had a slightly odd face when i said that the system was electric. I fear the EPC result with it too.
As per your suggestion, I have an AC company coming to our new property soon (full conversion so central air heating/cooling), i'll extend their visit to this house too for a first hand opinion, as they install ASHP. Perhaps we can get a weak ASHP installed in tandem with the system boiler or similar...
If you are getting a forced air system for heating and cooling (which is effectively the same as a wet ASHP just designed for air and not water) would that not make your existing wet system redundant? That kind of system is very common in the states, just not here.
You just need to figure out the hot water which could be an ASHP (with immersion boost) or just straight immersion.
Worth checking with the installer when you speak to them.
You just need to figure out the hot water which could be an ASHP (with immersion boost) or just straight immersion.
Worth checking with the installer when you speak to them.
You are crossing the properties there - the new one is a full conversion of an empty agricultural building, hence going straight to central air for that one - made no sense to me to do anything else when starting from scratch. Not related other than that i'll be having a meeting about the design of that building with them soon, so will tag this on.Our existing house is the one with the legacy wet system. Water heating is immersion now, and i doubt would ever be questioned, i am very happy to leave that. It does have a diverter so that the system boiler can heat the tank through its coil, but this clearly makes no sense to bother with as it is, although it would mean that an ASHP could take the edge off, to reduce immersion load...
Ah yes, now that makes sense, I remember you posting about that in another thread.
Yes it’s worth having a chat with the installer to see what’s in the world of the possible.
Your right the full electric heating will put some buyers off. Does it have a heat store so you can utilise eco7 (that will take the edge off somewhat) or is it just heat on demand?
Yes it’s worth having a chat with the installer to see what’s in the world of the possible.
Your right the full electric heating will put some buyers off. Does it have a heat store so you can utilise eco7 (that will take the edge off somewhat) or is it just heat on demand?
Its just heat on demand, normal meter, normal (albeit large) circuit from the main CU.
It operates just as the oil one did, but without the bulk, smell, and faff, it is silent, etc, i love it.
Slightly expensive to run, but not mega, partly offset by the oil boiler it replaced likely being inefficient. I'd not change it at all if we didn't plan to sell, but with it being unusual for a larger property to be direct electric, ASHP seems like a get out of jail free card with being a current buzzword and also what is fitted to any decent newbuilds now. My thinking is that i wonder if we can plumb it to operate in tandem with the existing electric boiler
It operates just as the oil one did, but without the bulk, smell, and faff, it is silent, etc, i love it.
Slightly expensive to run, but not mega, partly offset by the oil boiler it replaced likely being inefficient. I'd not change it at all if we didn't plan to sell, but with it being unusual for a larger property to be direct electric, ASHP seems like a get out of jail free card with being a current buzzword and also what is fitted to any decent newbuilds now. My thinking is that i wonder if we can plumb it to operate in tandem with the existing electric boiler
I like his videos although he does go on a rant at times. If they want people to spend a small fortune on replacing a gas boiler then the minimum requirements should be that it is either cheaper to run or offers similar performance (preferably both).
Air source heat pumps don't seem to meet those criteria unless your house has been built with a heat pump installation in mind. We need realistic alternatives if gas boilers are going to be scrapped and just making gas more expensive isn't the answer.
@Jez, I had 2 small single radiators replaced with doubles and an upright designer radiator installed. To be honest the bedroom radiators are turned down quite low otherwise the rooms get too hot. The shower room radiator was one of the replaced doubles and it didn't really need to be a double as I have had to turn the valve almost off as that room gets to warm otherwise. The property is 1930's solid double brick construction with an extension to the side. It is double glazed with only the extension windows being K glass. Of the old part of the building only 1wall has 25mm insulation, bedroom ceilings are insulated. Probably the way the system was originally installed by British Gas, the downstairs radiators take longer to heat the rooms. For me the output temp through the radiators is fine as I like it a bit cooler than the wife. The only cons is the sound that it makes(like a washing machine on a long spin cycle) as it had to be installed under a bedroom window because we have flooding issues occasionally.
Under the recent Green Home scheme from the Gov I was only offered underfloor insulation help despite having a 30 year old boiler and single glazing. ASHP went out the window with no incentive. So now I'm considering a smart boiler like the Mixergy plus a simple switched boiler to replace the current one. Then in the future I can consider other sources of energy as they are developed.
Current smart tariff would offer 5p/kwh for electricity which is close to gas. Solar and battery storage are alternatives as the costs continue to fall.
Current smart tariff would offer 5p/kwh for electricity which is close to gas. Solar and battery storage are alternatives as the costs continue to fall.
The gas boiler was due to be replaced, so we went with the ASHP to be "greener". The government scheme for using it meant that it was only the upfront cost that was expensive. But if you factor in the cost of a new boiler and a few new radiators it would have been about half of what we would have spent. Now we have no gas meter so no standing charge on that, just electric and the RHI scheme at the minute is paying us to use it. Rough cost for 3-4 bed house with some insulation is £350 during cold months £68 summer months and that is for all electric usage for 2 people. That is monthly, we receive £320 a quarter from the scheme
@tonys your experience is interesting. Did you do a total cost of ownership calculation before you went ahead?
We were quoted £8k for a ASHP and an additional £2k of remedial work (swapping rads) that wouldn’t need doing for a gas to gas replacement. Converting to a unvented cylinder would cost us £4K (neighbour just had it done), a straight replacement is £2k.
When I did the maths the ASHP was a lot more expensive in terms of total cost of ownership.
The RHI is helpful but i didn’t make up for all the costs of the system and remedial work that needs doing in my property. You also have to fork out for it all upfront, e.g. £2k-£4K for gas vs £8k-£10k for ASHP.
The financial risk of a premature in the ASHP is substantial because you can’t get the RHI again.
We were quoted £8k for a ASHP and an additional £2k of remedial work (swapping rads) that wouldn’t need doing for a gas to gas replacement. Converting to a unvented cylinder would cost us £4K (neighbour just had it done), a straight replacement is £2k.
When I did the maths the ASHP was a lot more expensive in terms of total cost of ownership.
The RHI is helpful but i didn’t make up for all the costs of the system and remedial work that needs doing in my property. You also have to fork out for it all upfront, e.g. £2k-£4K for gas vs £8k-£10k for ASHP.
The financial risk of a premature in the ASHP is substantial because you can’t get the RHI again.
I am very interested in the way that your system didnt need overhauling @tonys, as well as your house sounding thermally poor as mine is. As i say, zero appetite here to disrupt the relatively new radiators, and especially not the megaflo etc.
Current thinking, pending a meeting with our AC company, is that it is very possible and infact preferable to install one in tandem with the electric boiler. This covers a very cold period where the ASHP may fall behind. Hoping then that the ASHP might keep the system chugging along when the temperature is the typical south eastern temperatures of 10-15c - ie, the system barely has to work, but you do need it to maintain 20-21c inside. This is the bulk of the year.
Current thinking, pending a meeting with our AC company, is that it is very possible and infact preferable to install one in tandem with the electric boiler. This covers a very cold period where the ASHP may fall behind. Hoping then that the ASHP might keep the system chugging along when the temperature is the typical south eastern temperatures of 10-15c - ie, the system barely has to work, but you do need it to maintain 20-21c inside. This is the bulk of the year.
The cost of the system install was just under £16,000 3years ago. This was for the 16kw ASHP, extra heat unit inside, unvented 150lt hot water cylinder, pipework for the install,wireless heat pump controller, wireless thermostat and replacing any or all of the radiators if necessary.The running cost was based on the gas bills at the time and to be honest they weren't much different from just using the ASHP. We save a bit as we got rid of the gas meter so that we didn't have to pay a standing charge just to have the meter. You may be correct that it is more expensive to run but the system is good even in the cold weather, as it was designed to operate efficiently in the British winter weather. It would be no different to having an air con running summer and winter to cool and heat rooms. Obviously the monthly cost decreases as the weather changes, I think the most we payed this year was £363 in the really cold spell.
Yes but add the electric and gas bills together it wasn't a big difference. Just before we had the heat pump installed we were with BG and EON. Now with Bulb, although due for a look at costs again. When we had the gas boiler we were spending on 2 standing charges aswell as the tariffs at least this way we only have the 1 bill
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There was some kind of scheme in the area I'm living in now - some people had air and some ground source - at least around here those that had air source aren't particularly happy with it - I don't really know the ins and outs of why. People who had ground source seem much happier with it.
A £16k install cost and £350 a month sounds horrendously expensive.
I thought the £1 a day my electric boiler cost to keep my thermal store topped up between the stove being lit was expensive.
As has been said above, if you need the subsidies to make it a cost effective install then it's not a long term solution.
I thought the £1 a day my electric boiler cost to keep my thermal store topped up between the stove being lit was expensive.
As has been said above, if you need the subsidies to make it a cost effective install then it's not a long term solution.