Domestic Air-Sourced Heating

Mar 14, 2005
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In a thread about the ban on the sales of Internal Combustion Engine (ICE) cars in the UK by 2030, a point was made about the use of heat pumps to improve the efficiency of cabin heating in Electric Vehicles (EV's). One member began to discuss the problems of using Air Sourced Heating in domestic premises and how that must affect EV's in the same way.

Anyone who's interested in the subject might find these two Youtube video's of interest. These are both quite long, but he does impart quite a lot of technical information and background.

View: https://www.youtube.com/watch?v=7J52mDjZzto


View: https://www.youtube.com/watch?v=7zrx-b2sLUs
 

Sam Vimes

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As with most things care needs to taken in understanding the true benefits of these types of system. I'm making some generalisations here as technology changes all the time and what's below was true last time I looked.

Marketing likes to focus on the top level efficiency as provided by the Coefficient of Performance but in reality its the Seasonal Coefficient of Performance that provides a better indication. Efficiency in colder air temperatures tends to drop.

Also consider the needs of providing hot water and space heating.

Air to water systems can come in two flavours - low temperature of high temperature.

Low temperature systems are intended for underfloor heating and while they could be used with radiators, the radiators may have to be larger than a conventional system. Hot water tanks may also have to be larger and water temperature needs to be carefully considered to ensure high enough temperature to kill off Legionella bacteria - this may require an electric boost.

High temperature systems can be used more successfully with conventional radiators but the higher temperatures in the system usually result in a lower SCOP figure.

Consider also that conventional gas boilers can provide continuous instantaneous hot water whereas Air to Water systems that I'm aware of provide energy to either space heating or hot water, with hot water usually given priority. Once the tanks empty it will need to be fully heated to get more when you may only want small amount.

Consider also is the unit cost of the power source. According to some sources the price per kWh of electricity is 7.19p for an air source heat pump - and for a conventional gas boiler 4.16p, taking into account the efficiency of either system.

As a result the head line efficiency figure can be less than acheived in reality and the cost differential in fuel types may erode the savings further.

That's not to say that installing ASHP is a bad thing evironmentally but the cost impact to the end user needs careful assessment. Just like the cost of electric vehicles is putting off the adoption of them for some folks the potentially higher install cost of an 'gas boiler' equivalent ASHP system may put off installing this retrospectively. How long would the cost savings have to run for to pay back the difference in system cost? Hopefully before the system needs replacing.

New builds in the future, if the government gets its way, will have to have Heat Pump systems which may push up the cost of a new build. (Discussion of the noise of hundreds of condensers on an estate of new builds crammed together for another time - as is the surge in electricty as everyone comes home and turns the heating on at the same time as wanting to charge a couple of electric cars :) )

In my opinion the issue of environment in respect of energy usage of homes needs addressing from at both ends of the problem. Not just coming up with more efficient ways of using more energy but better ways of using less.

Enough :)
 
Jul 18, 2017
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If we had a choice, we would opt for the gas heating. We don't think our air source heating is that effective as on cold days it frosts over and is not effective at warming the home. Result is that we have to switch on the gas heater to bring the temperature up again. Hence an earlier thread of mine a couple of months ago.
 
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Sam Vimes

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Buckman, I recall your earlier thread.

Systems may have improved but friends here who have similar systems installed within the last 10 years or so report similar things.

We installed andAir to Air system in our village hall about 8 or 9 years ago after having a consultant in to assess our needs. It was never warm enough and also noisey. We received a 100% grant to cover costs but it died last year and the easiest, i.e. cheapest / less agro option was to go for the same system, but larger, since we had to pay for most of it ourselves.

Due to you know what we've not had a chance to use the hall this winter so not sure what the result is.
 
Jul 18, 2017
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Buckman, I recall your earlier thread.

Systems may have improved but friends here who have similar systems installed within the last 10 years or so report similar things.

We installed andAir to Air system in our village hall about 8 or 9 years ago after having a consultant in to assess our needs. It was never warm enough and also noisey. We received a 100% grant to cover costs but it died last year and the easiest, i.e. cheapest / less agro option was to go for the same system, but larger, since we had to pay for most of it ourselves.

Due to you know what we've not had a chance to use the hall this winter so not sure what the result is.
We have had ongoing issues with ours a Mitsubishi and the issues have never been fully resolved. When they fitted the system we had to leave straight away for a funeral. On our return our home had been flooded out due to a poor connection. That was the start of our troubles. Next was it freezing up and not be able to get to 20C. It is suppose to defrost automatically but this has never happened despite technicians coming out several times. Eventually we gave up on it. Also quite noisy at night.
 
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If we had a choice, we would opt for the gas heating. We don't think our air source heating is that effective as on cold days it frosts over and is not effective at warming the home. Result is that we have to switch on the gas heater to bring the temperature up again. Hence an earlier thread of mine a couple of months ago.
It not been a total loss - what about the days when you've been able to heat your home adequately with the ASHP you will have spent considerably less than if you'd heated it by other means.

I have a gas fired central heating system which is more than capable of heating the whole my house in the coldest of weather. I have it zoned, but even so I choose to use the central heating to cover the base load to maintain about 17C to 18C downstairs, and use a storage radiator to add a degree or so to the living room where my wife spends most of her time. Cost for cost its more effective to use economy 7 to boost the room, than to run the main boiler and end up heating parts of the house when its not needed.

Its a question of being smart and using what resources you do have to their best advantage.

I would certainly consider ASHP when I next need to consider changing my primary heat source.
 
Jan 31, 2018
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I'd love to but from what I see/ Read it uses a fair amount of electricity in cold weather, and provides only just enough if enough heat and needs to be run constantly. With our 15 year old house on radiators designed for oil, we have a good system that costs around 600 a year at the mo-current oil prices-has been a lot less, can be more and would love to get off oil but bottled gas is very pricey and air source just doesn't seem good enough for me-yet-and v pricey too. We can have a new oil boiler for less than 5k-unless things improve am afraid that'll be the way we go.
 
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It not been a total loss - what about the days when you've been able to heat your home adequately with the ASHP you will have spent considerably less than if you'd heated it by other means.

I have a gas fired central heating system which is more than capable of heating the whole my house in the coldest of weather. I have it zoned, but even so I choose to use the central heating to cover the base load to maintain about 17C to 18C downstairs, and use a storage radiator to add a degree or so to the living room where my wife spends most of her time. Cost for cost its more effective to use economy 7 to boost the room, than to run the main boiler and end up heating parts of the house when its not needed.

Its a question of being smart and using what resources you do have to their best advantage.

I would certainly consider ASHP when I next need to consider changing my primary heat source.

No fun have the AS heating frozen up for over a week and it struggling to produce heat to keep the home at 20C. It has happened. During the summer months our electric bill is about £45 on average however in winter this can shoot up to over £130 and we have not had a really bad winter since 2011. Cheapest tariff is straight forward metering and avoiding E7 or E10.
Just to add heating has been on since 5am and temperature in lounge area is 19.5C although it reads 20C in passageway where the control radiator is situated. Worst heating system we have ever had, but when in a rural area not much choice so you live with it!
 
Nov 11, 2009
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It not been a total loss - what about the days when you've been able to heat your home adequately with the ASHP you will have spent considerably less than if you'd heated it by other means.

I have a gas fired central heating system which is more than capable of heating the whole my house in the coldest of weather. I have it zoned, but even so I choose to use the central heating to cover the base load to maintain about 17C to 18C downstairs, and use a storage radiator to add a degree or so to the living room where my wife spends most of her time. Cost for cost its more effective to use economy 7 to boost the room, than to run the main boiler and end up heating parts of the house when its not needed.

Its a question of being smart and using what resources you do have to their best advantage.

I would certainly consider ASHP when I next need to consider changing my primary heat source.
We do a similar thing. The gas central heating is set low and if we switch it to schedule it runs from from 0730-2130.(a rarity). All rooms have thermostatic valves and the main thermostat is mobile. In the lounge we had a coal/ log burner removed and a high efficiency 4kw gas fire installed. So when we settle for the evening the lounge gas fire may be lit and quickly brings the room to a comfortable temperature as by then the boiler has been providing base warmth. . I tend also to use the TRVs like switches. Such as yesterday there were seven for lunch so the TRVs in the dining room were wound fully open and the thermostat taken into that room. Similarly when we have anyone to stay bedroom radiator TRVs are opened up. We pay £80 pm for energy and periodically receive a refund. The next step is to remove the kitchen range which has its smallest electric oven at 68 litres. A gas cooker will go in the hole as well as a much needed extra storage unit and walk cupboard.
 
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No fun have the AS heating frozen up for over a week and it struggling to produce heat to keep the home at 20C. It has happened. During the summer months our electric bill is about £45 on average however in winter this can shoot up to over £130 and we have not had a really bad winter since 2011. Cheapest tariff is straight forward metering and avoiding E7 or E10.
Just to add heating has been on since 5am and temperature in lounge area is 19.5C although it reads 20C in passageway where the control radiator is situated. Worst heating system we have ever had, but when in a rural area not much choice so you live with it!

My thermometer next to me is at 19.4deg C. No form of heating since Top Gear came on when we decided it was warm enough. But the cooker had been on a lot yesterday and the heating was on during the day as we had visitors for lunch. Our place is very well insulated and the external walls take the sun over three sides.

9A304475-B9B5-4C86-8CD6-BDBA79C7DB87.jpeg
 
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I would say that the same about our bungalow it well insulated the reading was 18.5 and we had no heating at all today we get sun at the back that is south facing and then it moves arounds all day to each its own
 

Sam Vimes

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If you're contemplating installing an Air Source to Water Heat pump system consider the actually running costs as well as the installation costs - envinronmental issues aside.

An ASHP system could be - optimistically - about 4 times as efficient as a gas boiler system ( Gas boiler at about 85%: ASHP best case 350% efficient). But then consider that Gas may be 1/4 the price per kWh compared to electricity. The savings, if any, may not be that great.

Different fuel types can make better savings. Consider the information here about relative costs:-


If there are savings to be made in running costs due to selection of a good tarriff, consider how long it would take to pay back the difference in system costs. It may be that the ASHP system cost more than £5k compared to a gas boiler and even if you could save £500 per year - doubtful in my opinion - it would take 10 years to recover the additional cost before you see the real savings.

Without being disrespectful to anyone 'cos I can only infer how old some of you are - are we actually going to see the benefit :) I remember my father buying a new TV when he was 98 and was offered the option of a 5 year warranty. He had a good sense of humour to suggest that he would go before the TV.
 
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Like when we moved into this house the EPC had given a few improvements of which ground source heat pump was one. From the payback period of 25 years it would have to be totally reliable abs maintenance free over that period. Which is a nonsense. Current EPC are not much more than a simplistic box ticking excercise. But unfortunately there’s a lot of people likely to be swayed by them and install new stuff using the higher than required government schemes interest rates. Where payback is outweighed by interest.
 
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Othercive,

I too have TRVs on every radiator, and some rooms like unused bedrooms are set considerably lower than rooms we use until they are needed. Convenienetly my last energy supplier provided energy benchmarks for different types of property and habitation levels, and on balance I was using only 75% of the energy other similar households were using on heating.

Sam
Undoubtedly ASHP is unusual by present day standards do tend to have a premium cost attached to them. I am certain this will change as Gov't puts more pressure on the buildings standards to incorporate better energy management systems and sources. Its going to be a long game, and the benefits of waiting will be a bigger experience base that means the planning of an installation will be better informed, and the cost comparisons with alternatives will improve.

When ASHP and GSHP become more mainstream and are being manufactured at scale, there will be significant falls in plant costs. But at the same time as fewer older traditional gas and oil boilers are installed their costs will ramp up as they loose the benefits of scale. Eventually they will effectively meet, but almost certainly at a higher real price than we see now for gas /oil systems.

Buckman,
As was discussed when you first told us of your heating problems, I'm inclined to think your system may not be working correctly or was not specified correctly for your needs when it was installed.
 
Jul 18, 2017
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Buckman,
As was discussed when you first told us of your heating problems, I'm inclined to think your system may not be working correctly or was not specified correctly for your needs when it was installed.
There is that possibility, but it was installed by so called experienced experts. As said we have had them out of numerous occasions, but the same issue returns year after year so have basically given up and have learnt to live with a horrible expensive system. In a previous similar size property that had gas highest bill was about £80. Normally summer was about £30 on average.
Prior to the rubbish ineffective air source heating we had storage heaters and they worked a lot better than the air source heating. Temperature in lounge is now 19.9C nearly 7 hours after heating came on.
 
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There is that possibility, but it was installed by so called experienced experts. As said we have had them out of numerous occasions, but the same issue returns year after year so have basically given up and have learnt to live with a horrible expensive system. In a previous similar size property that had gas highest bill was about £80. Normally summer was about £30 on average.
Prior to the rubbish ineffective air source heating we had storage heaters and they worked a lot better than the air source heating. Temperature in lounge is now 19.9C nearly 7 hours after heating came on.
Still at 19 deg c. No heating since last night but good solar at present warming the outside walls. 😀
 
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