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Buy a spare Combi Boiler or go "Heat Pump"?


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Evening all

Given the recent government "lets be the first in the world to ban the sale of new gas boilers" joke I wondered if it would be worth while purchasing a spare combi boiler as I'm not convinced by the heat pump as a viable solution to heat a home.

Has anyone any real world experience as to the Heat Pumps ability to heat a home and provide hot water (or do you need a separate electric immersion heater/tank) in terms of;

1) Initial purchases/installation costs

2) Installation/site requirements

2) long term running costs

3) Reliability

Whats peoples thoughts?

Andy

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I was thinking about this today and I decided I would run my combi to death and hopefully by then ( see the next 10 years through ?)

then see what the full throttle drive of technology gives us by then. Hopefully the heat pump scene has moved on significantly due to competition.

think in the mean time I’ll stock up on logs and a stove top kettle.

 

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I have a friend who had a very expensive house built (£1,000,000+) and he kept telling me about the wonderful (and expensive) heat pump system he had installed.

In 4 years it has broken down twice.

Interestingly his system is monitored from an office somewhere in Eastern Europe and the first he knew of a problem was an eMail from them. Sounds efficient, but the spare parts took weeks to arrive and be fitted. While the system was down he had to rely on the (expensive)backup electric immersion heaters that were fitted.

Maybe things have improved since then.

 

Charlie

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Apparently there are a lot more factors to consider.  Reading up on the subject raises the following:

How well insulated is the house?  Older houses with poorer insulation will require considerable upgrade to make them suitable for the lower heat levels provided by a heat pump.

Is this to be a full new installation or an add-on to existing?  Ideally a heat pump is used with underfloor heating, not with radiators. Installing underfloor in an older house is a big undertaking. Underfloor heating is not as controllable as radiators and incurs a considerable time lag between demand change  and heat change. Existing radiators would need replacing with larger ones as the water does not get so hot and so needs a larger area.  

Can you have a ground-source heat pump? Much more efficient but also very expensive and needs the ground area to install.

Are you (or your neighbours) noise averse? Air-source heat pumps have fans which may be annoying during the quieter hours. 

You will need separate top-up for water heating, probably from an immersion heater.  The water temperature must be raised above 60C occasionally, to kill legionella.

Air source heat pumps can ice up as the temperature drops towards zero - particularly in the UK where we get damp cold conditions. In that case the efficiency can drop below unity meaning the system uses more power than would a simple electric heater because it has to defrost itself as well as heat the house. 

https://www.davidstrong.co.uk/web_documents/air_source_heatpumps1.pdf

https://pricethisplease.co.uk/air-source-heat-pump-installation-cost/

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My son in Norway has a big open plan house in  an exposed location, it is heated by an air source heat pump and a log burner. The heat pump supplies heat to a hot air blower as opposed to the UK system of radiators and it works well, BUT it uses a fair amount of electricity.

I looked at fitting one here but was quoted £14,000 and they wanted to fill my garage up with some great big unit to supply hot water to the radiators, I could buy a kit iin Norway which are sold in most DIY stores, similar to my sons with a hot air blower for about £3,000. I worked out the running cost of the electricity compared to the cost of the oil that we currently burn and the difference was  negligible so I shall wait untill the oil fired boiler finally gives up the ghost and then take the campervan for a Scandinavian holiday

George 

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I'm 71 and lived in my house the last 47 years since buying it.

It's only had 2 gas boilers in that time, the first one we bought after 18 months used from a moggy miner who received coal allowance, and had it removed from his house only 6 years old.

This first gas boiler NEVER broke down and the only servicing was carried out 2 yearly (I'm not made of money). This boiler was replaced after 22 years because we noticed some furring along the boiler sides inside it's case and we replaced the boiler as a precaution. The second and current gas boiler has been in use over this last 25 years and NEVER broke down and the servicing is carried out 2 yearly (I'm still not made of money) I'm going to continue with it as long and far as possible...notice any similarity between both these boilers  ?

Because these older boilers are so basic I'm pretty sure we'll get at least another 10 years out of it, and although not as efficient as the current combi boilers they have the advantage of being err...bomb proof.

I've been involved in a housing project for 12 learning disabled tenants which had a combi boiler each and replaced 31 boilers in just over 9 years. I felt bad for the contracted premises management team who had undertaken to replace these boilers at their expense in the contract but they were unsurprised, "it's what we budget for with combi boilers amongst our housing stock" they said. 

There is plenty of information available which lists all the disadvantages of air pumps and ground pumps when fitted to old housing stock (mine was built 1937) although it does have cavity walls which have been filled with insulation. Summing it up it looks like getting the capacity of heating to rival current radiator outputs will be a good trick, more difficult on an air pump than a ground pump with the GP model costing about £15k more than an air pump. Also more insulating required and lots of disturbance for fitting required with rooms dismantled. As an incentive the £5k grant being proposed for 90,000 homes will fall a long way short, and the government may well find that inventing and developing new technology is not as easy as closing their eyes and hoping it happens. 

They will no doubt incentify us by increasing the price of gas ( so buying a gas boiler as insurance will probably not work out financially, it costing more to run year on year) so as to be equal with the already inflated price of electricity, which allows them to pay a small amount of rebate to owners who committed to solar panels upon their roofs, which the entire country is paying for hidden within these inflated electricity prices. I still wind up my neighbour who has solar panels by offering him a £5 note when I pass him..."to cut out the middleman", he doesn't smile. This particular ponzi scheme has now reached critical mass and the government will be reneging upon rebate agreements and changing the regulations to allow them to slide out from repayments as they can.

Mick Richards 

Edited by Motorsport Mickey
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My house is well-insulated and I looked into this extensively. Over here the consensus is that if you can run water temperatures below 50 degrees C, the heat pump can economically heat a building. The lower the water temperature the higher the efficiency. Outside average temperatures affect that too. In my case the outcome was not very convincing but (all) new houses are built with heat pumps here.

An alternative I’m looking into is to install an air/air heat pump, more commonly known as an airco, which can use the excess electric energy my PV panels generate annually. It could be used to reduce natural gas consumption in fall and spring.

That is  cost effective for me, pay back in 7 years.

Waldi

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As far as I can work out you will need to demolish your house and build again to passivhaus standards in order to get a heat pump to work.

My house is mid 19th C. Quoted £40K for a ground source heat pump with no guarantee it would actually be capable of heating the house. Oh yes, I could externally insulate but then the solid walls would likely suffer from not being able to breathe. I'm not made of money either.

The whole concept is nonsense with the housing stock we currently have.

Jerry

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I had an airsource heatpump installed in a previous property - approx 10 years ago.  This had nothing to do with being green .... I had an oil powered boiler that had to be replaced and nobody would touch it as the oil tank was inside the house (which met regs at the time) and I was eligible for a decent grant so it was cost effective.  

Aside from the heatpump failing twice in 8 years (cracked heat exchanger and then panel stopped) it was OK. 

A few things to know: 

- it did reduce my outgoings
- your water is not as hot and so you have to adapt to this.  Baths and washing up needs kettle top up or immersion heater (you shoudl use teh later at least once a week to get temp above 65 to prevent legionairres).
- linked to above, your rads do not get as hot so it takes a lot longer to heat your house (so you need to stop it from getting too cold by having the heating on all the time in the winter )
- if it gets really cold, it is not efficient ant not good at heating your house effiicenlty if you have let it get cold

I know live with mains gas and wouldn't go back to an airsource heat pump

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I've also looked into this several times, and got some quotes earlier this year. There are loads of factors and "known unknowns" (crucially, how confident are you that the particular HP you have installed will actually achieve the performance spec in real world conditions). It's really hard to find situation-specific reliable advice other than relying on what the sellers/installers say.

The costs are still considerable (over £20k in our case quoted a while back for a 16kW ASHP, admittedly a high-spec one, with a replacement HW tank and associated gubbins and labour to create a hybrid system - we would retain our gas boiler for peaks, with the ASHP giving base load). As we are on mains gas (rather than oil or bottled gas) there is no financial advantage in short-medium term and it on a per-tonne basis it would be an expensive way to reduce carbon. Not helped by living in SE England where the power grid mix isn't very conducive at the moment - if we were in N Scotland where almost all electricity is renewable it would be a different matter.

My impression is that, while GHSP is more efficient that ASHP, the extra capital cost and disruption even for a borehole rather than ground loop doesn't make it especially attractive. I imagine most installations will end up being air source, I believe that's the case in France where the rate of uptake is far ahead of UK at this point.

I may go back and get fresh quotes and just do it next year on a "no regrets" basis with the partial cost offset of the new £5k grant scheme from April. The costs are forecast to come down a lot and hopefully there will be more real world testing to validate the claimed efficiencies, but someone has to be the early adopters meanwhile to get to that point.

The government's strategy announced yesterday points towards tilting tax/incentives towards electricity-for-heat as the grid becomes C-neutral, and the stated aim is to achieve that full decarbonisation by 2030 (you can of course debate whether that will happen, but it looks to me achievable at least within the next 15 years depending very much though on the nuclear part). The problem will still remain, as fully said already, that a lot of UK housing is problematic for HPs due to poor insulation and legacy CH pipework, although a lot of houses built more recently will be able to retrofitted so it depends if you're half-full or half-empty in your view, to me the take-up needs to be progressive but doesn't have to all happen in all places at once.

Let's not start on hydrogen, seems to me a major distraction and govt is only assuming a quite small exploitation of that so I've put it out of my decision matrix for now. I hope I haven't upset the H and fuel cell fans too much! :)

Nigel

 

 

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Insulation comes first for me. Heat pumps have to be sized to the calculated needs of the building: too small and the building is too cold, too large and it cylcles on and off damagingly. HPs still too experimental for me. Next comes  a replacemnt oil-fired c/h boiler. Finally masses of solar PV on roofs and garden to heat water and supplement the oil in winter. "Free" solar PV most of the year allows for expensive oil in winter, and ca 90% reduction in oil consumption.  Am investigating whether solar PV on a clear winter day  can heat a water tank in a single room to provide evening warmth without the pfaff of plumbing. Biggest reduction may come from letting rooms run cold in winter, and heat only when occupied. 

My guess is HP will rapidly get a bad name and a compromise made: fit lots of solar PV and insulation and  then be allowed (expensive) gas in depths of winter.

 

 

Peter

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Hybrid solutions are applied here: maintain your existing gas/oil fired heater for coldest days and run the HP on the warmer days. DIY packages start at ca 3000 Eur, and as an example, a professionally installed 5kW Daikin ASHP (as hybrid besides your existing boiler) will cost some 5000 Eur -/- 2000 euro sponsoring by the government (so 3000 net expenditure).

Waldi

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If this current bunch of w**kers running the country are really committed to being green and saving the planet why do they not dictate that all new build homes have heat pumps solar panels and car charging points as standard ?

Cheers Chris

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1 minute ago, Chris Hubball said:

If this current bunch of w**kers running the country are really committed to being green and saving the planet why do they not dictate that all new build homes have heat pumps solar panels and car charging points as standard ?

Cheers Chris

Chris 

They are all the same go figure one of the largest share holders of the BBC not in his name a organisation that is guaranteed a income by law is the largest voice they should ban the fee and let them stand on their own two feet 

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2 hours ago, Peter Cobbold said:

...Finally masses of solar PV on roofs and garden to heat water and supplement the oil in winter. "Free" solar PV most of the year allows for expensive oil in winter, and ca 90% reduction in oil consumption... 

Out of interest, do you have a rough yardstick on how much PV you could buy for the cost of a typical ASHP installation (let's say £10k for that, net of the subsidy)? My impression is they are in pure financial terms not attractive at domestic scale - assuming of course you're not living entirely off-grid in the first place.

I used Energy Saving Trust website to model a 6kW PV array (up front cost around £8k) at our SE England location, almost south facing, and the lifetime net benefit was negative in £ terms. It might save a tonne or so of CO2 a year, but an expensive way to do that - a 16kW heat pump has similarly unattractive financials but that would save several tonnes of carbon a year.

Or am I comparing apples with some other fruit? (It's Not Easy Being Green.)

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I'm getting the impression heat pumps are still almost experimental, far from reliable and incapable with dealing with low temps or able to provide water hot enough to bath or wash up with. This is to the point where alternative heating is required like gas or likely more expensive electricity so what's the point of change for change sake?

Grant or no grant which I suspect will be means tested. Result if you have or continue to work hard and saved for retirement you will get nothing so will be expected to stump up the full cost which will be far more than simply replacing an existing gas boiler. I see people trapped in the financial middle freezing as they can't afford the change. The same people who politicians of any colour need to think about next time an election is due. Politicians as usual jumping the gun for media sound bites with no real understanding of the implications for normal people never mind the planet. If they were that bothered the debate would be around reducing the world population and by default Co2 emissions. But that's not PC is it.

Personally I think I will buy a spare combi or two for spares and run mine it until I have no choice, stock up on logs and anything else that will burn and invest in as much insulation as I can install. It would seem more logical to help people insulate and burn less gas while using an existing pipeline infrastructure rather that creating a new electricity grid with all the increases in Carbon Footprint  this would cause.  Or perhaps repurpose the gas grid to burn Hydrogen but then who wants to live next door to a potential Hindenburg disaster!

Andy

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6 hours ago, jerrytr5 said:

As far as I can work out you will need to demolish your house and build again to passivhaus standards in order to get a heat pump to work.

Passivhaus definition is that you do not need a heating system at all. The heat from humans living in it is quite sufficient to keep the house warm all winter. The classic story is that if you have a Passivhaus standard house and are cold, then get a dog.

Heat pumps are far from "experimental" every house has one, it is in the fridge. Most air-conditioning systems are heat pumps. 70 year old technology? Just a new application, not rocket science. The vapour compression cycle is well understood and has clear limitations of efficiency when applied to home heating applications, no magic step changes in efficiency are going to appear overnight, despite what Boris says. The greater the difference in the temperature of the evaporator and condenser the less efficient it becomes. Typical coefficient of performance is up to 4 for home heating with underfloor heating, about 3 with low temp radiators and even less when heating hot water up to 65C.

As others have said the key is to reduce the underlying heat demand by house design and to reduce the required differential temperature by heating system design.

As our house is 17th century, I plan to keep my gas boiler for as long as possible, perhaps we should buy a spare now......

Mick

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4 hours ago, Bleednipple said:

Out of interest, do you have a rough yardstick on how much PV you could buy for the cost of a typical ASHP installation (let's say £10k for that, net of the subsidy)? My impression is they are in pure financial terms not attractive at domestic scale - assuming of course you're not living entirely off-grid in the first place.

I used Energy Saving Trust website to model a 6kW PV array (up front cost around £8k) at our SE England location, almost south facing, and the lifetime net benefit was negative in £ terms. It might save a tonne or so of CO2 a year, but an expensive way to do that - a 16kW heat pump has similarly unattractive financials but that would save several tonnes of carbon a year.

Or am I comparing apples with some other fruit? (It's Not Easy Being Green.)

I did a back-envelope guesstimate of a solar PV powered seasonal heat store capable of capturing summer PV output and then delivering 1 kW 24/7 through winter.It needed £12k of pv, a 300,000 litre insulated water store..............but in theory could work without electrickery if the dwelling were built on top of the tank. Total cost makes it impractical. But it was simple ! and zero running or maintenance cost.

Current thought is to insulate and  draft-proof as heavily as possible and retreat in winter to kitchen-living room with all waste heat from fridges, freeezer,  washing, cooking, captured. Solar PV to run dhw and aircon cooling in spring to autumn. Maybe add more PV to run appliances, its cost is likely to fall and performance to improve (eg perovskite) . Keep oil boiler for c/h and  dhw in winter when PV poor--to-zero.

Peter

 

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17 minutes ago, Peter Cobbold said:

I did a back-envelope guesstimate of a solar PV powered seasonal heat store capable of capturing summer PV output and then delivering 1 kW 24/7 through winter.It needed £12k of pv, a 300,000 litre insulated water store..............but in theory could work without electrickery if the dwelling were built on top of the tank. Total cost makes it impractical. But it was simple ! and zero running or maintenance cost.

Current thought is to insulate and  draft-proof as heavily as possible and retreat in winter to kitchen-living room with all waste heat from fridges, freeezer,  washing, cooking, captured. Solar PV to run dhw and aircon cooling in spring to autumn. Maybe add more PV to run appliances, its cost is likely to fall and performance to improve (eg perovskite) . Keep oil boiler for c/h and  dhw in winter when PV poor--to-zero.

Peter

 

Peter,

My house and garage face south,

I find solar gain makes a big difference, living in a south facing room is much warmer.

When I insulated my south facing garage doors, the garage became cooler.

Insulation works both ways.

Peter V W

ps, sun always shines in Wales

 

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3 hours ago, Peter V W said:

Peter,

My house and garage face south,

I find solar gain makes a big difference, living in a south facing room is much warmer.

When I insulated my south facing garage doors, the garage became cooler.

Insulation works both ways.

Peter V W

ps, sun always shines in Wales

 

All but one room in the cottage faces south -they built wisely 300 years ago !- and the 18 inch thick stone walls means we need no space heating even in evenings from April-Sept. As you say fitting insulation risks losing that benefit. Perhaps the insulation needs to be seasonally adjustable - but how? Peter

 

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This article says it all.......

https://www.msn.com/en-gb/money/other/roger-bisby-heat-pumps-are-one-of-the-biggest-con-ive-seen/ar-AAPIIYn?ocid=mailsignout&li=BBoPWjQ

We live in a listed building so no external insulation allowed, no double glazing. Solid walls. Can't put insulation on inside of walls because that will make walls colder and lead to condensation within the wall and structural damage. Garden not big enough for horizontal ground source heat pump. Solid rock under house so vertical ground source not feasible. Air pump systems I have looked at require 20 amp supply fuse. Main house fuse only 60 amp. Would need to upgrade power supply to house in order to install system or put in an electric car charger. Can't install solar panels on a listed building or in a conservation area.

Other than the above perfectly feasible!

We have a gas boiler, log burner, immersion heater, electric heaters, open fire with back boiler linked into central heating, camping stoves and oil lamps and candles for when we have power cuts (quite often with ageing overhead cables to village). We also have plenty of thick winter clothes we can wear and one of the highest tog rated quilts on the bed. Temperature indoors is usually about 15C although we can get it up to almost 20C with the heating on full. You get used to it and don't feel cold when you go outdoors in the winter. Mind you when it drops below 10C indoors and your breath fogs then it can get a bit nippy.

Keith

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18 minutes ago, keith1948 said:

Mind you when it drops below 10C indoors and your breath fogs then it can get a bit nippy.

I’m sure that many of us here where children in the early 1950’s, when our bed would be up against the window and we’d wake up in the morning and have to scratch the ice off the INSIDE of the glass to look out.

Kids today don’t know what cold is.

Charlie.

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