April 2022 5k towards heat pump

[Moxi]

Not started a thread for ages so apologies if this is in the wrong place, already common knowledge or not allowed ?

Any of the above let me know and I will correct or remove

That aside just seen this in the IMechE magazine

https://www.imeche.org/news/news-articl ... Oifb0TAQnw

Moxi

[Oliver90owner]

It’s been in the news for some weeks.

A claimed insufficient scheme for the numbers required to make a difference.

Prices will be raised because the ‘certified’ suppliers will be limited in numbers and pile on the profit - so likely cheaper to go it alone before very long.

At an overall COP of barely 2 ( for air source), leccy will be expensive cf gas, so only ground source systems are anywhere near economic cf gas.

Boreholes are much more expensive initially, and a 5k grant is a far smaller % of the installation cost, but the COP should be much improved over an air source system. Still need to run on cheap rate leccy.

Air source don’t advertise the regular defrosting that is needed in the UK climate - they extoll their virtues in cold but dry regions, not close to zero Celsius and high humidity.

Under-floor heating is preferred for maximum economy.

New installations will obviously work better than retro-fitted ones.

They are not there yet!

[nowty]

There is very little info yet about exactly how this system will operate. I think the main requirement is that you are ditching a gas / oil boiler for a heatpump based system.

I suspect you only get the full £5k grant if your system costs at least £10k, so my concern (like with the RHI scheme) is its a scammers charter, you get a £5k air source system installed for £10k.

[Paul_F]

• £5k grant for air source, £6k for ground source.
• If you're getting a COP of 2 you've got a really screwed up installation. For a retrofit installation a COP of 4 is realistic based on monitored data over 12 months.
• Defrosting is a minor issue - might be a problem if you really screw up the system design, but if sized correctly it'll be fine.
• Underfloor helps, but oversized radiators give very good performance in most houses.
• Requirement is that it's your main heating system. Retrofit and self-build qualify, new build does not.
• No sign of a minimum spend yet, looks like there probably won't be but it'll need to be MCS accredited and that will increase the costs for the installer in paperwork, etc.

[Andy]

Most of the air source heat pumps that I have found with a detailed data sheet don’t work well below freezing. And up in scotland we can spend a lot of time there. So it really depends on where you live as to how well they will perform.

[nowty]

Paul_F, is that link to your own property ?

Whilst I agree that a COP of 2 is poor, my own experience is a COP of about 3 (with oversized radiators) with a GSHP and aligns favourably with the second phase of the Energy Savings trust report on an average of 44 MCS installations of ASHP and GSHP.

Achieving an average COP of 4 is quite an achievement and I doubt to be realistic on retrofit unless you can upgrade your house to passivhaus standards.

https://www.energysavingtrust.org.uk/si ... 281%29.pdf

[Force10]

Andy

Would be interested in a chat as I am looking at a GSHP system as I can’t convince myself the an ASHP will cut it up here (Aberdeenshire) inspite of what a couple of companies say. For exactly the reasons you site.

[Ken]

• £5k grant for air source, £6k for ground source.
• If you're getting a COP of 2 you've got a really screwed up installation. For a retrofit installation a COP of 4 is realistic based on monitored data over 12 months.
• Defrosting is a minor issue - might be a problem if you really screw up the system design, but if sized correctly it'll be fine.
• Underfloor helps, but oversized radiators give very good performance in most houses.

There are eg of HPs that work and those that do not. As the ref says it needs to be designed correctly but then you have the problem of practicalites,

1) If you do not have underfloor heating a huge increase in rad sizes are required, how much depending on how correctly sized they were in the first place. However if you want to achieve the low flow temps to achieve the high COP quoted then perhaps about 3X is reasonable. Most people do not even do 2X and run higher temps and therefore lower COP. And higher DHW temps.

2) Large bore 22mm pipes are required to allow the necassary flow rate.

3) a suitable size pump needs to be installed and if the house was twice as big or detached then that is not insignificant power drain.

4) Many people have colder winters than 5.5C and around 0C you are definetly into defrost territory. Also a 5kw HP would not cut it on most retrofit houses and did not cut it with the idol John Cantor either.

So for many people the ideal conditions in that ref cannot be obtained, eg i have a small bore pipe system but i would also have a house full of rads.

It works for the ref because of the small house and small heat requirements of a terraced house and therefore a doable rad area.

One thing i have learnt about this is that whereas with gas boilers its mostly one size and one way of working suits all the HP is the direct opposite of this.

PS my daughter lived in a flat in the middle of a block and never had the heating on although she did have a plasma tv.

[Paul_F]

Paul_F, is that link to your own property ?

Whilst I agree that a COP of 2 is poor, my own experience is a COP of about 3 (with oversized radiators) with a GSHP and aligns favourably with the second phase of the Energy Savings trust report on an average of 44 MCS installations of ASHP and GSHP.

Achieving an average COP of 4 is quite an achievement and I doubt to be realistic on retrofit unless you can upgrade your house to passivhaus standards.

Nope. Trystan Lea is the guy behind OpenEnergyMonitor, and he's done a superb job on documenting what he's done and logging the performance of the heat pump. It's a very well designed system though (he had a lot of help from John Cantor), so the flow temperature is only 30°C and the hot water is only heated to 42°C - still more comfortable than the original heating system by all accounts though.

[Oliver90owner]

As I see it, it is in the depths of winter where the COP needs to be upheld - and I don’t see much evidence of that.

Efficiency claims are not clear as to whether defrosting sessions are include for calculating the COP. Quoting overall yearly figures is likely totally misleading - that it is high in summer is not too enchanting if it is p. Poor in winter.

Let’s see some more honest figures than those that give ‘averages’ or ‘overall’ COPs. It is the times of maximum usage (mid-winter) when frosting problems occur and temperatures are low, that really count. Like how much cheaper is air-source heating than gas? The only way, as I see it is while on a cheap night rate for leccy or with lots (and I mean “lots”!) of PV installed, to lower the take from the grid.

To me, advertising is like that of cars - they always show off the top speed, even though the speed limit in the UK is a maximum of 70mph (and often less).