Soldato
You need ground pumps in this country, air source are a waste of money
Heat Pumps: anyone have one/thought about it?
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Citation needed.
Ground source are significantly more expensive to install and barely any more efficient these days.
Where they work better is for a ‘district’ heating set up for something like a tower block where the cost of drilling the bore hole can be shared between a number of people. For a single dwelling, not so much, bar a few odd exceptions such as a really large, high end property.
The efficiency at mild temperature there would be little difference between extracting or pumping out heat on both type of system as the temperature gradient is no difference between a 15c air and 15c ground. This is true for a few months of the year, when it comes to cold winter you will need to use a lot more energy to extract heat from 0c to heat the house vs extracting heat from the ground loop which if sized correctly at temp of 15c. This period is also where heat is needed to most and the heaviest usage therefore overall efficiency will drop and no where as sexy as the 300% we see on all the studies.
I am sure as times go heat pump technology will get better and better, at least now a days air heat pumps (domestics) can work up to -20c where that was not possible 10 years back.
I am sure as times go heat pump technology will get better and better, at least now a days air heat pumps (domestics) can work up to -20c where that was not possible 10 years back.
here’s the thing, a correctly installed and sized Morden air source heat pump should be achieving 350%-400+% across the year (usually quoted as SCOP - seasonal coefficient of performance).
It’s the hot water that lowers the %, not the heating, it would be higher otherwise. It needs to get it hotter than what you’d want to run your heating loop which reduces efficiency but that’s usually a fraction of the demand.
It’s the hot water that lowers the %, not the heating, it would be higher otherwise. It needs to get it hotter than what you’d want to run your heating loop which reduces efficiency but that’s usually a fraction of the demand.
Soldato
I would only fit a ground source one if i was having a self/new build property done, but would probably just stick to solar and batteries
That is the magic bullet, if that 400% can be achieved then problem solved as I already have solar and battery plus solar farm and wind farm investment coming online in the next 6-12 months.
Interesting read from solarblogger.net
One thing we know for sure is that in the UK electricity costs much, much more per unit than mains gas. Nottingham Energy Partnership has the average standard rate for electricity in September 2021 at 23.3p/kWh (kilowatt-hour), and mains gas at 4.39p/kWh.
The efficiency of a modern condensing gas boiler is often said to be around 90%, but since we are interested in real-world heat pump performance, we should compare like for like. A field trial of the seasonal efficiency of 60 boilers by the Energy Saving Trust in 2009 gave a value of 82.5% for combi boilers.
Using this efficiency one unit of gas heating costs 4.39/0.825 = 5.32p/kWh.
For heat pump heating bills to cost no more than a gas boiler, the efficiency of the heat pump would need to be higher than 100% x 23.3/5.32 = 438%, but what efficiency do heat pumps achieve in practice?
The Energy Savings Trust and the Department of Energy and Climate Change (now called BEIS), set out to answer this question in 2008. The first large-scale heat pump field trial in the UK aimed to determine how heat pumps perform in real-life conditions. The year-long field trial monitored technical performance and customer behaviour observed at 83 domestic properties across the UK.
The resulting report (Getting Warmer: a field trial of heat pumps), published in 2010, found that the average efficiency for an Air Source Heat Pump (ASHP) was 220% (page 16), although this was revised down to 182% by a subsequent analysis published in 2012. This second report corrected errors and removed data provided by ‘Manufacturer A’ which were felt to be from systems that had been hand-picked, carefully optimised and installed in the homes of the manufacturer's own staff. (See Detailed analysis from the first phase of the Energy Saving Trust’s heat
Despite the best efforts of the authors to put a gloss on things (“the best performing systems show that well-designed and installed heat pumps can operate well in the UK”), the results were highly disappointing.
Above was old info but then this
Around 14,000 Heat Pumps were installed with funding from the RHPP, and 700 of these (around 5% of the total) were subject to a detailed monitoring study. The study reports an average efficiency based on SPFH4 for the ASHP in the sample of 241%.
However it also reveals that the heat meters used in the study were calibrated for water and not the antifreeze-mix with which most would be installed . The estimated 4-7% over-statement of performance was not corrected in the published result. Applying a mid-range 5% correction, would make the true average SPFH4 nearer 229%.
Reassuringly, this is still closer to the second EST study than the first and suggests that the changes made to the industry standards in response to the disappointing performance of systems in the first study had fed through into a higher general performance, across a reassuringly large sample of installations.
Taking efficiency from this most recent study of 229%, the annual energy costs for a house heated by a heat pump will be (23.3/5.32) x (100/229) = 1.91 times higher than the same house heated by a gas boiler.
So, even after industry steps to eliminate design errors, carefully optimising the installation and coaching the householder how to use the heat pumps, running costs are still double those of a gas heated property.
What hope do we have when we scale up to install heat pumps in the huge numbers envisaged by UK policy makers? If installations increase from 30,000 a year currently to the 300,000 a year called for by the government will the heat pumps perform as well as those in the second study, or is it more realistic to anticipate performance closer to the first study?
"Taking efficiency from this most recent study of 229%, the annual energy costs for a house heated by a heat pump will be (23.3/5.32) x (100/229) = 1.91 times higher than the same house heated by a gas boiler."
We need that Magic bullet of 400+% all year around to make ASHP work and not just new built but average UK home to replace technology like gas boiler.
How Much do Heat Pumps Cost to Run?
Advocates of heat pumps regularly claim that a ‘well designed, well installed and properly run heat pump will cost no more to run than a gas boiler’. A careful re-reading of this sentence will show you that three things have to go right for heat pumps to cost no more than gas heating.One thing we know for sure is that in the UK electricity costs much, much more per unit than mains gas. Nottingham Energy Partnership has the average standard rate for electricity in September 2021 at 23.3p/kWh (kilowatt-hour), and mains gas at 4.39p/kWh.
The efficiency of a modern condensing gas boiler is often said to be around 90%, but since we are interested in real-world heat pump performance, we should compare like for like. A field trial of the seasonal efficiency of 60 boilers by the Energy Saving Trust in 2009 gave a value of 82.5% for combi boilers.
Using this efficiency one unit of gas heating costs 4.39/0.825 = 5.32p/kWh.
For heat pump heating bills to cost no more than a gas boiler, the efficiency of the heat pump would need to be higher than 100% x 23.3/5.32 = 438%, but what efficiency do heat pumps achieve in practice?
Real World Heat Pump Performance
The Energy Savings Trust and the Department of Energy and Climate Change (now called BEIS), set out to answer this question in 2008. The first large-scale heat pump field trial in the UK aimed to determine how heat pumps perform in real-life conditions. The year-long field trial monitored technical performance and customer behaviour observed at 83 domestic properties across the UK.
The resulting report (Getting Warmer: a field trial of heat pumps), published in 2010, found that the average efficiency for an Air Source Heat Pump (ASHP) was 220% (page 16), although this was revised down to 182% by a subsequent analysis published in 2012. This second report corrected errors and removed data provided by ‘Manufacturer A’ which were felt to be from systems that had been hand-picked, carefully optimised and installed in the homes of the manufacturer's own staff. (See Detailed analysis from the first phase of the Energy Saving Trust’s heat
Despite the best efforts of the authors to put a gloss on things (“the best performing systems show that well-designed and installed heat pumps can operate well in the UK”), the results were highly disappointing.
Above was old info but then this
Real World Heat Pump Performance - Third Time Lucky?
In March 2017 UCL Energy Institute published its Final Report on Analysis of Heat Pump Data from the Renewable Heat Premium Payment (RHPP) Scheme.Around 14,000 Heat Pumps were installed with funding from the RHPP, and 700 of these (around 5% of the total) were subject to a detailed monitoring study. The study reports an average efficiency based on SPFH4 for the ASHP in the sample of 241%.
However it also reveals that the heat meters used in the study were calibrated for water and not the antifreeze-mix with which most would be installed . The estimated 4-7% over-statement of performance was not corrected in the published result. Applying a mid-range 5% correction, would make the true average SPFH4 nearer 229%.
Reassuringly, this is still closer to the second EST study than the first and suggests that the changes made to the industry standards in response to the disappointing performance of systems in the first study had fed through into a higher general performance, across a reassuringly large sample of installations.
Taking efficiency from this most recent study of 229%, the annual energy costs for a house heated by a heat pump will be (23.3/5.32) x (100/229) = 1.91 times higher than the same house heated by a gas boiler.
So, even after industry steps to eliminate design errors, carefully optimising the installation and coaching the householder how to use the heat pumps, running costs are still double those of a gas heated property.
What hope do we have when we scale up to install heat pumps in the huge numbers envisaged by UK policy makers? If installations increase from 30,000 a year currently to the 300,000 a year called for by the government will the heat pumps perform as well as those in the second study, or is it more realistic to anticipate performance closer to the first study?
"Taking efficiency from this most recent study of 229%, the annual energy costs for a house heated by a heat pump will be (23.3/5.32) x (100/229) = 1.91 times higher than the same house heated by a gas boiler."
We need that Magic bullet of 400+% all year around to make ASHP work and not just new built but average UK home to replace technology like gas boiler.
All those studies have identified that not putting in a control for installer training was a mistake and as is massively skews the resulting performance. The issue is generally not the heat pump, it’s literally everything else connected to it (pipes, rads, pumps, controls etc.), if it’s not correct, performance tanks. To put it simply, many installers just don’t have the training to install them correctly.
You generally don’t have that issue on a gas system, you’ll probably get 80% out of pretty much any boiler regardless of whether the rest of the system is a complete cluster or not.
Suggest watching this which explains why poor installers are a massive issue and something I highlighted earlier in this thread:
https://youtu.be/RlcvncWvNUQ?si=wCoY0-uqSSn1VUO8
As I said, a well installed system will perform. That said, I’d prioritise solar over installing one because solar helps to reduce the running costs a lot.
You generally don’t have that issue on a gas system, you’ll probably get 80% out of pretty much any boiler regardless of whether the rest of the system is a complete cluster or not.
Suggest watching this which explains why poor installers are a massive issue and something I highlighted earlier in this thread:
https://youtu.be/RlcvncWvNUQ?si=wCoY0-uqSSn1VUO8
As I said, a well installed system will perform. That said, I’d prioritise solar over installing one because solar helps to reduce the running costs a lot.
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Lets see the next study of ASHP which hopefully includes more installation from "heat geek trained" installer. I am always skeptical of information from people who will have finical gain from selling courses and views. I would predict that a lot of installation would not be going ahead as ASHP efficient would not be at 400% unless the entire system needs to be changed as part of a proper install. This may even be change of hot water consumption habits as a 400%+ efficient ASHP does not work like a gas boiler with hot water storage for instant hot water.
Soldato
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- 27 Mar 2013
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I think as people have stated its not worth an older property. I have a house built in 96, so not that old but all my pipes are microbore (but the house is reasonably well insulated). I still dread to think of the cost of installation as I suspect I'd need bigger rads to cope with the lower temps. I also have a hot water tank which I quite like as I have a nice power shower so that would add more complexity/ cost (not sure if heat pumps supports hot water tanks, although I don't see why they wouldnt). I also don't know how you position a pump without it being an eyesore, we live in a detached so not too bad but not sure how you'd manage in a terrace unless it fed all houses in the strip.
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Watching and learning from the youtube video where Skill Builder vs Heat geek the only time they discuss real life efficient numbers is Part 1 @ 45:00 and Part 2 @ 25:00. Heat Geek mentioned that SCOP of 3.5 can be achieved with house of poor insulation or design and 5 can be achieved with houses with special design radiator and insulations to achieve average of 4 and above. With just changing the overall hot water running at 45 and 55 is enough to affect SCOP massively.
I would definitely keep an eye on their monitored SCOP installations tho, there are2 system over 1 year old with SCOP of 4+ . Will need to dig deeper in what is the install and if any changes to the existing heating system to achieve that, one of those install is a 1930 house like mine I think.
I would definitely keep an eye on their monitored SCOP installations tho, there are2 system over 1 year old with SCOP of 4+ . Will need to dig deeper in what is the install and if any changes to the existing heating system to achieve that, one of those install is a 1930 house like mine I think.
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SCOP is not impacted by heat loss or lack of insulation. That is a myth that needs to be debunked. You design the system to the heat loss.
More heat loss = bigger heat pump (or boiler) + bigger rads + bigger bore pipes to enable the required flow rate. Obviously less heat loss is better and that is no different to gas.
@theone8181 - heat pumps only support using cylinders for hot water with unvented cylinders being the preferred option - there is no hot water on demand option. Also from what I understand from my own research, if your heat loss is below 6kw, you can get away with microbore to the rads. My 2003 detached is below 6kw with me only topping up the loft insulation from 100mm to ~300mm. This is one of those, your results will vary depending on your specific property and heat demand. You will probably need new rads, most of mine are single panel, they’ll all need to be swapped to double. I have a few doubles which will need to be enlarged in terms of footprint.
More heat loss = bigger heat pump (or boiler) + bigger rads + bigger bore pipes to enable the required flow rate. Obviously less heat loss is better and that is no different to gas.
@theone8181 - heat pumps only support using cylinders for hot water with unvented cylinders being the preferred option - there is no hot water on demand option. Also from what I understand from my own research, if your heat loss is below 6kw, you can get away with microbore to the rads. My 2003 detached is below 6kw with me only topping up the loft insulation from 100mm to ~300mm. This is one of those, your results will vary depending on your specific property and heat demand. You will probably need new rads, most of mine are single panel, they’ll all need to be swapped to double. I have a few doubles which will need to be enlarged in terms of footprint.
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Man of Honour
I'd need to upgrade so many radiators since the house is old that it's just not cost effective for me at the moment. Though we have solar panels so it would help a little with the cost. Even with the 5k grant it would still be over 10k of cost and I just can't afford it.
More heat loss mean more heat needed from radiators to maintain comfortable home temperature. This can be achieved by running the existing radiator hotter (gas boiler do that 70-80c) or having a bigger radiator with bigger pipe more flow and keeping the radiator flow higher (ASHP 55c). It is the higher water temperature needed which kills the SCOP, just like using ASHP for hot water will achieve lower SCOP.
This is like a catch 22 running the system at 45c and house is freezing will achieve SCOP of 5 , running the system at 70c and house warm will achieve SCOP of 3 and of course this is a over simplified explanation. Heat geek even mention of setting the water tank temperature to 45 which is just above shower temp to make it efficient..... It is not as simple as most would made to believe ASHP is 400% efficient and will safe money and environment or picking the right installer would achieve that, with a house like mine built in the 1930s and a household of 4 it would mean a entire heating system installation plus full installation installation to achieve the efficiency.
The difference is that gas boiler operates at higher temperature of 80/60c and the rest of the radiator system are design to run at that. What we need is a ASHP which can achieve 400% efficiency and just bolt it on the outside wall and connect it to the existing boiler connection and output hot water at 70c
The issue with your points is that they ONLY apply with a system which has not been designed correctly or you are just trying to bolt on a help pump to an existing system designed for a higher flow temperature. That's exactly why heat pump installs perform poorly. Running a heat pump at 45C doesn't mean the house is cold IF it has been designed correctly. The flow temp just determines how quickly the heat is moved from the heat source to in the house.
If you ran your condensing gas boiler at 45C with proper weather compensation and set back temperatures, it would also be way more efficient. That's also why your 95% efficient boiler isn't 95% efficient, it's lucky if its even 85% efficient.
The difference is that gas boiler operates at higher temperature of 80/60c and the rest of the radiator system are design to run at that. What we need is a ASHP which can achieve 400% efficiency and just bolt it on the outside wall and connect it to the existing boiler connection and output hot water at 70c
You wouldn't design a heat pump system to go above 45C if you can help it. If you are changing the radiators which is likely anyway, you'd just put in rads that enable a 40C flow temp. Sure if they can run at 55C and not kill the SCOP then it could make retrofitting A LOT cheaper but that's all. If you would still try and target 40C if you could as it will be more efficient. you can get high temp heat pumps but you'll be topping out at a SCOP of ~3 instead of 4+.
You really don't want to be running radiators up at 80C, that is just unnecessary and frankly dangerous, the same applies to hot water at 70C. You can get a full thickness burn in around 10 seconds at 60C, obviously its less when hotter. Hot water is fine at 50C (with a weekly legionella cycle) even then you'll be mixing in cold water in almost all uses. You can't put your hander under a 60C tap for more than a second, its utterly pointless.
I turned down the hot water on my nan's combi from 65C to 50C, she complained the bath wasn't hot enough because she didn't need to put much cold in before she got in it. It took 3 attempts to explain why heating water to 65C and then cooling it down to 40-45C with cold water for a bath was not a good use of money.
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80/60 is what the boiler designed to work, to make it working to energy efficient A rating temperature will be lower. In our house all year around it is set to 60c, it is the temperature of water leaving the boiler and not at the radiators. There are 12 radiators in our house and yes they run hotter than most new built but my 1930 house needed that to achieve the desire room temperature. Thermostat on our wall usually dictates radiator temperature by controlling the flow and not by the boiler set temperature. Our water tank is set to 60c and that is to make sure legionella bacteria risk is kept to minimum, if we keep the hot tap running for long enough it will be enough to burn you but that did not happen so far in the past 12 years including bringing up 2 offsprings. it is a pet hate for me personally with hot and cold separated taps, who uses that? All my shower has thermostatic valves as we all hate the change of hot and cold when water pressure changes. This is more of problem of this generation of labeling bleach bottle do not drink or elderly losing their independence and no one to look after and got burn when using hot only taps....
Back to the OP and topic, most people talk about replacing gas boiler with a ASHP and not replacing the house heating system. If doing house insulation to improve efficiency of ASHP (ONLY) then just stick with Gas boiler and do the insulation anyway as you have the same inefficiency boiler but spending way less on energy bill and no need to change anything else. Changing hot water using habit is not as simple as just add less cold water to a bath, with 3 bathrooms and everyone using hot water at once in winter times is not uncommon in my house. We have a high pressure combi boiler with a big tank and it is designed in mind that it will never runs out of hot water with all bathroom in use, this is where a ASHP fails or at least failed at efficiency of 400%.
To me I think there are way too many variable to say ASHP is the way forward for existing gas boiler systems, we have a big garden 35m x 12m and it is just green lawn with no trees with wet clay soil ( we know because we did extension 10 years ago) a Ground source with higher efficient COP to start with and merge with what we have existing system would get me to think about changing my gas boiler.
Back to the OP and topic, most people talk about replacing gas boiler with a ASHP and not replacing the house heating system. If doing house insulation to improve efficiency of ASHP (ONLY) then just stick with Gas boiler and do the insulation anyway as you have the same inefficiency boiler but spending way less on energy bill and no need to change anything else. Changing hot water using habit is not as simple as just add less cold water to a bath, with 3 bathrooms and everyone using hot water at once in winter times is not uncommon in my house. We have a high pressure combi boiler with a big tank and it is designed in mind that it will never runs out of hot water with all bathroom in use, this is where a ASHP fails or at least failed at efficiency of 400%.
To me I think there are way too many variable to say ASHP is the way forward for existing gas boiler systems, we have a big garden 35m x 12m and it is just green lawn with no trees with wet clay soil ( we know because we did extension 10 years ago) a Ground source with higher efficient COP to start with and merge with what we have existing system would get me to think about changing my gas boiler.
Soldato
I'm fairly confident that heat pumps require a thermal store to work. I don't think you can have one without. But my experience is on the commercial side of things so I guess domestic might be different.
Exactly. The reality is that if you have a poorly performing house, it will just take longer to heat up at lower flow temperatures, which is what heat pumps put out. But that's the same with a highly insulated or a poorly insulated building, just the time taken will be longer in the latter example.
Unfortunately some houses are so badly insulated that it loose heat faster than you put it in, the only way to heat it faster is the raise the radiator temperature or increase the radiator size and sometime the pipe work. Increase operating temperature will drop the Heat pump efficiency and increase radiator size or pipe size may not always be practical. Most months our normal radiators will function and dare I say anything above 10c outside we will just need a bit of top up heat from the radiators, but heat pump needs to work for us and not we work around it. I think there is already enough discussion in the past few pages to make know that heat pump does not work on its own as boiler replacement, it may require a system change (radiator and pipe) and the right environment (house insulation/heat loss) to make it work to the claims of efficient. One can just plonk it in the boiler location and run it at 60c but it will cost more to run than a gas boiler.
I have an email from Octopus offer of Daikin heat pump install, no details yet as it requires a survey. I will pay 500 refundable deposit and after the survey if goes ahead it will be a Daikin heat pump, water tank and all necessary radiator changes. I will pay £6000 and government grant of £5000. I will likely to go ahead if all the calculation are done correctly and not just sticking a finger in the air and have all my radiator changed if needed to get the go ahead. My gas boiler is 12 years old, radiators are a mix of 12 years old and 30+years old. It will be interesting and happy to update this thread.
I already have 4kw solar and 12kw of battery running on Octopus Go, 1kw co-op wind farm starting hopefully next year and 500w solar co-op starting 2025. Interesting times ahead
Soldato
Yeah fair point. In which case, a homeowner is probably better off investing in fabric improvements than in changing their energy source. That should offer them a net benefit I would imagine.
I'd love to get a heat pump but I think the financial case only stacks up if you're going to be in the property long term, which I won't be.
This article is interesting: https://www.theguardian.com/environ...ssil-fuel-systems-in-cold-weather-study-finds