Air Source Heat Pumps Do Not Work

[Oz07]

I wonder if there will be a last minute rush on gas boilers in 24/25?

[joe90]

54 minutes ago, Oz07 said:

How cheap @joe90?

£850, still on original pallet and shrink wrapped from manufacturer. Kingspan dropped out of the market and sold off all their stock. Actually made by Carrier of America who make zillions of these and air con units ?.

[joth]

10 hours ago, SteamyTea said:

No, I am interested in why there is a reluctance to fit them.

I think you already answered this.

 

1/ for whatever reason, the evidence is that people regularly install poorly designed systems that under perform

2/ so we can deduce it's hard to design a system that is guaranteed to work well

3/ most lay persons (and self builders) lack the skills and experience to be sure they can design their own system. It's probably the only system they'd ever design so not worth formal training on how to DIY it

4/ there's a dire shortage of professional system designers with proven track record.

 

RHI is explicitly designed to solve #4 (NOT to reduce cost of ownership, as people tend to think) which in theory is the way we (as a country) get out of this conundrum

BUT it puts up the "up front" cost of ownership, which combined with the drawbacks listed above makes it extremely unattractive idea to the cautious customer

 

[dpmiller]

1 hour ago, Oz07 said:

 But id say there's a lot more people out there that could fit a boiler but not an ashp.

 

 

why do you say that? 2 pipes and a couple of wires. No need for any accreditation or fancy signoff.

[SteamyTea]

47 minutes ago, Oz07 said:

I wonder if there will be a last minute rush on gas boilers in 24/25?

Only on new builds.

It does not change existing installations as far as I know.

[SteamyTea]

35 minutes ago, joth said:

2/ so we can deduce it's hard to design a system that is guaranteed to work well

Possibly it.  It may be hard to convince people that after being told they need everything less powerful i.e. vacuum cleaners, light builds, kettles, cars; to save the environment, to then come along and say, 'well actually, you need a 10 kW system, so we are fitting a 15 kW one.

 

I think it is up to the manufactures to get this message across, and offer a scaleable system i.e. 4kW increments.

[joe90]

47 minutes ago, joth said:

1/ for whatever reason, the evidence is that people regularly install poorly designed systems that under perform

people? I think you mean so called professionals without a track record in ASHP installs. Plenty of cowboy plumbers out there that instal gas boilers etc.

 

47 minutes ago, joth said:

2/ so we can deduce it's hard to design a system that is guaranteed to work well

Why, I designed my own system with the help of a few people on this forum and I have no formal training.

 

47 minutes ago, joth said:

3/ most lay persons (and self builders) lack the skills and experience to be sure they can design their own system. It's probably the only system they'd ever design so not worth formal training on how to DIY it

 

See no 2/

 

47 minutes ago, joth said:

4/ there's a dire shortage of professional system designers with proven track record.

Is there?, yes it’s a fairly new tech knowledgely but quite a few of us here managed it. It’s not rocket science.

 

47 minutes ago, joth said:

makes it extremely unattractive idea to the cautious customer

not if they do their homework about who to employ, same as finding any trades person IMO

Edited November 6, 2020 by joe90

[Gone West]

I wouldn't fit an ASHP in an old poorly insulated house because I wouldn't want all the walls covered in radiators.

[joe90]

2 minutes ago, PeterStarck said:

I wouldn't fit an ASHP in an old poorly insulated house because I wouldn't want all the walls covered in radiators.

yes any system is as good as the calcs done about heat loss etc.

[Oz07]

1 hour ago, joe90 said:

£850, still on original pallet and shrink wrapped from manufacturer. Kingspan dropped out of the market and sold off all their stock. Actually made by Carrier of America who make zillions of these and air con units ?.

Not bad. My boiler about a bag of sand then 45 each year to keep 10 yr warranty. I think @joth has articulated the concerns better than me. Also as @PeterStarck says they do need larger area to work due to lower temp. 

 

I thought the argument was if it's a well insulated home and gas is avail use that, then swap to ashp if and when gas becomes obsolete. 

[Oz07]

29 minutes ago, SteamyTea said:

Only on new builds.

It does not change existing installations as far as I know.

Maybe a rush of as designed Sap submissions before the cut off them a bit like 2015 when part l changed. 

[PeterW]

58 minutes ago, joth said:

I think you already answered this.

 

1/ for whatever reason, the evidence is that people regularly install poorly designed systems that under perform

2/ so we can deduce it's hard to design a system that is guaranteed to work well

3/ most lay persons (and self builders) lack the skills and experience to be sure they can design their own system. It's probably the only system they'd ever design so not worth formal training on how to DIY it

4/ there's a dire shortage of professional system designers with proven track record.

 

RHI is explicitly designed to solve #4 (NOT to reduce cost of ownership, as people tend to think) which in theory is the way we (as a country) get out of this conundrum

BUT it puts up the "up front" cost of ownership, which combined with the drawbacks listed above makes it extremely unattractive idea to the cautious customer

 

I’ll counter those, and provide a bit of insight .. 

 

1. this poor design isn’t just for ASHP it is heating systems in general. I see modern new build houses with 3 en-suites and 200 litre hot water tanks, and small system boilers that are “eco” installs who wonder why they run out of hot water every day. The same houses have slightly smaller rads than 15 years ago, but not by much, and they have not been sized correctly. The rad calculations under BS EN 442 and the sizing calculators are woeful - have a look here at a calculator from the UKs largest supplier. Note the “standard delta T” is 50c, so unless this is altered for a heat pump and properly understood then you have issues from the outset. 
 

2. it isn’t difficult, it just takes time. And time is money. People don’t want to pay for proper design for M&E, and I see this regularly. To run a whole set of correct sizing calculations for heat loss for UFH for an average 160sqm house will take about 4-5 hours assuming the client has the plans in CAD format. From that, the design can be done but it probably in all takes up to a day to get the remainder done. That’s £3-400 of fees, and is usually pre-sale and I would say 90% of customers expect this for free. The UFH suppliers do this for “free” but they don’t actually use anything more than standard values for walls etc and it is very broad brush. I’ve seen designs from two suppliers get it wrong by a factor of 40%, and when challenged they say it’s only a guide ..... only a guide for something you’re going to bury in 5 tonnes of concrete and cover for ever ..?!! The second point is about guarantees, and that is something that is nigh impossible to achieve to 100% accuracy. MCS used to say sized to to 99.5% from memory, but that’s based on historic data. How can you predict weather patterns 4 or 5 years ahead ..? The issue there is you oversize and then consequently over price and the client invariably goes for the cheapest option... it’s always an amusing conversation with a client who tells you they “think the quote is too expensive as Fred Smith is £1000 cheaper” yet you’ve got a raft of calculations and Fred has an envelope with some scribbles on it .. Oh and just because you asked for a quote, but didn’t want to pay for it doesn’t mean the calculations belong to you, you haven’t bought that ..!!

 

3. Heat loss design is probably one of the easiest calculations to do as it is methodical and requires little more than a set of plans, a ruler and a spreadsheet. Once you know the heat loss of the building, calculating the input is relatively simple (ie size of boiler / ASHP etc) as it has to be larger than your worst losses. Then the UFH or rad design comes next, again if you download LoopCAD yourself, you can do this in a weekend. I would hazard a guess than anyone who can use a spreadsheet can get to a good approximation of a design over a few evenings and well within the 30 day trial period of the software. It comes back to the questions of time and cost. 
 

4. I’d argue there isn’t a dire shortage of designers, I would say there is a shortage of clients prepared to pay for it. Most M&E designers I know don’t work on domestic clients as they neither understand what they are getting for the money, or want to pay the fees. I’m always amazed at the fees people are prepared to pay architects for a house that looks good, but when built it performs like a bag of spanners. Unless you go down the PHPP route, very few even clients consider heat loss or overheating in a normal build, and a lot of questions on this forum are about that very issue and yet surprisingly people expect the answers from here for free .... and yet they are prepared to spend £’000 on something such as windows but won’t spend £’00 on ensuring they have hot water or a warm house ..?? On your point on RHI addressing the issue, that is completely incorrect. It has made it worse, as don’t forget, the worse the losses, the more the customer gets paid .. and no-one is going to “buy” a system that has no return on investment when it is supposed to be an incentive scheme to change. The calculations done are worst case, and usually by “surveyors” who have previously sold cheap double glazing or worse, and they are “checked” by someone certified who doesn’t validate the numbers. My own house was surveyed for solar, and despite the “surveyor” being told the attic had 400mm of insulation, the survey came back with 250mm .. and a note saying it was pointless putting any more down as it didn’t make the numbers any better !! RHI cannot alter a poorly designed heating system, it just changes the heating mechanism to one that has a lower delta T and you are back to square 1. 
 

ASHPs aren’t expensive when you consider what they do, and they aren’t complex either. @joe90, @ProDave and a few others have self installed and they are pretty much plug and play. Mine is a 9kW Mitsubishi based unit that has a power supply and a 24v call for heat. That’s it. The control box I built for it allowed me to set it to run at 50/75% load but tbh it sorts itself out and heats a 300 litre UVC and 80sqm of UFH, and does that fine. A lot of the newer units are self learning and they will use sensors in the outside units to maximise the system performance based on having a floor temperature and a DHW temperature and they will work without any external input other than a simple time clock. The issues arise when the systems are undersized, or when a customer wants to “run the heating” with the same programme as they had with a gas/oil boiler. Go back to the beginning, and when you realise a different delta T means a longer time to heat up, then you have an issue. The systems I’ve designed are maximised to use off peak electricity so for me it is about how the ASHP interacts with the fabric - if I was to chuck a 9kW ASHP on trad sized rads into the current build, operating twice a day during the day then it would both fail to heat the building and also cost 40-50% more to run.
 

The difference it was designed as a system, not as a standalone heat provider, and that is where the problems start. If you don’t start with a design on paper at the same time as your plans, then you will be forever playing catch up and the rest of the design will be a compromise. 
 

 

[Oz07]

Are you a system designer then peter?

[Ferdinand]

On 04/11/2020 at 22:15, Thedreamer said:

I burn a small trug of logs from about 6pm to 10pm.

 

I think that needs a surprisingly small amount of area to feed it.

 

I'd still like to know the mass (or volume) of timber in that. But let's do some approx. numbers.

 

If I take it as 150 days (ie 5 months of stove-evenings per annum) that is 150 small trugs per annum. I'll take a small trug as 10kg of timber.

At @SteamyTea's 4.5kWh heat output per kg of wood, that is 1500kg or 1.5 tonnes of wood per annum. That feels about right in terms of amount of wood.

At a convenient (say) midrange softwood density of 500kg per cubic metre that is 3 metres of wood per annum required. 

 

So what does it take to generate 3 metres of softwood per annum?

 

Looking at the Forestry Commission Yield Tables, you can see that you get 3 metres just from thinnings on a plantation of approx 0.3 Hectares (ie just under an acre) as long if your (say) Sitka Spruce trees are 35 years old. And the main crop will still contain 300 cubic m of standing timber per Hectare, so you can get a maincrop as well. Or you could have a smaller patch and fell a bit every year.

 

I would say that half an acre of softwood should give you what you need for your evening fire on a continuing basis, containing 200-500 trees several decades old at 2m spacings. Ish. Very ish.

 

A quarter of an acre of your garden will make a big hole in your need. But you will be cutting at least one tree down every month ? . Below the Forestry Commission Licence level (assuming Scotlandshire is the same as Englandshire), but they are not especially small trees.

 

Ferdinand

 

 

Forestry-commission-yield-tables.pdf

[BotusBuild]

I spent a couple of years in the micro-renewable energy business (think solar PV, solar thermal, heat pumps, UFH for domestic and small commercial premises). I agree with what @PeterW has said above.

It was super important to get the heat loss calculations correct first, then move on to what would provide the heat input to the system, and what heat emitters you required (low temperature radiators or UFH, or (avoid whenever possible) oversized traditional radiators).

 

I have lost access to the heat loss calculator I used to use (it would likely be out of date now), so it would be great if some recommendations could be made for good current versions ?

[SteamyTea]

4 minutes ago, Ferdinand said:

At @SteamyTea's 4.5kWh heat output per kg of wood, that is 1500kg or 1.5 tonnes of wood per annum

Of dry timber, not sure if the FC table is for that.

And just for a giggle, work out the area of land needed, with PV on it, to supply the same energy at the same time of year.

[Ferdinand]

1 minute ago, BotusBuild said:

I spent a couple of years in the micro-renewable energy business (think solar PV, solar thermal, heat pumps, UFH for domestic and small commercial premises). I agree with what @PeterW has said above.

It was super important to get the heat loss calculations correct first, then move on to what would provide the heat input to the system, and what heat emitters you required (low temperature radiators or UFH, or (avoid whenever possible) oversized traditional radiators).

 

I have lost access to the heat loss calculator I used to use (it would likely be out of date now), so it would be great if some recommendations could be made for good current versions ?

 

The Jeremy Harris calculator is here:

https://forum.buildhub.org.uk/topic/439-fabric-and-ventilation-heat-loss-calculator/

[joe90]

I don’t think the majority of people instal wood stoves on a financial basis, I know we didn’t. We just love an open fire, goes with our “cottage” style, happen to have plenty of wood available fir free locally (neighbour is a tree surgeon ?). I would not consider one if I lived in a city/town because of the pollution but here in the middle of nowhere!!!! (I also drive a diesel ?).

[SteamyTea]

2 minutes ago, BotusBuild said:

I have lost access to the heat loss calculator I used to use (it would likely be out of date now), so it would be great if some recommendations could be made for good current versions

When I was working all this stuff out, I made my own spreadsheet.  Seemed to work.

 

Would be interesting to make up a calculator for working out UFH piping, then compare it to LoopCad.

[Ferdinand]

Just now, SteamyTea said:

Of dry timber, not sure if the FC table is for that.

And just for a giggle, work out the area of land needed, with PV on it, to supply the same energy at the same time of year.

 

I think my error margins are so large that the extra (or not) 5-20% mass of the moisture is De minimis. ?

 

(And with a single bound he was free).

 

I would put the overall error bars at +/-50% or so, but it is still a useful indication of scale - which is what I intended.

 

F

[SteamyTea]

Just now, joe90 said:

I also drive a diesel

Me too, but it is alright, as I live right by the 3rd word polluted road of 2017/8.

I would love to see the time serious data as there is no gas, so possibly it is all the people who burn coal and timber that is the real problem, not people with EURO4,5,6 cars (I missed the opportunity to work on the project a decade ago).

[Ferdinand]

22 minutes ago, SteamyTea said:

Of dry timber, not sure if the FC table is for that.

And just for a giggle, work out the area of land needed, with PV on it, to supply the same energy at the same time of year.

 

Very give or take I make it 200 panels.

 

Or one tenth of an acre. 

 

Ish.

 

F

[joe90]

7 minutes ago, Ferdinand said:

 

Very give or take I make it 200 panels.

 

Or one tenth of an acre. 

 

Ish.

 

F

On a cold winter evening I would still rather watch a real fire ??

[SteamyTea]

10 minutes ago, Ferdinand said:

Or one tenth of an acre. 

And now the area of an ASHP.

Or shall we call it no more than 1.5m²

[Ferdinand]

20 minutes ago, SteamyTea said:

And now the area of an ASHP.

Or shall we call it no more than 1.5m²

 

Not sure where we are going but I'll follow the White Rabbit.

 

No idea about ASHPs. I have a gas boiler :-). And some solar.

 

What would a GSHP area be for that - say 30kWh a day in winter?