System sizing based on actual consumption - a better way?

[billt]

1 hour ago, JamesPa said:

I registered for Heatpunk, its basically a same old same old MCS assumption based estimator, which will probably work fine if you have a house that is

 

a) of a consistent construction

b) hasn't had fabric upgrades, and

c) has the MCS assumed ventilation rates (are there any such houses?)

 

However it will get wrong, in some cases by a massive amount, houses which have been extended to different specs, have had partial fabric improvements or fabric upgrades to variable specs, or are not as leaky as MCS assumes.

 

I think you need to look at it more closely.

 

Our house is a hotchpotch of additions carried out at different times with different construction methods and it is possible to model that in the heat punk calculator.

 

You can enter fabric losses for each element in each room separately as well as air changes for each room. It should come up with a pretty accurate heat loss figure.

[JamesPa]

3 hours ago, PhilT said:

What, that oversizing is a major problem? My experience is quite the opposite. Billt's video rule of thumb suggests a 5.6 but I have an 11.2 and so far (2yrs) it's performed way better than design. I think modern scroll comp R32 or R290 heat pumps are so much more efficient at low output than they used to be. Looking at my graphs for early May there wasn't much comp cycling. Most of the"cycling" is simply the pump running for shorter periods and the room stat switching the pump off for longer periods when target room temp is met.

I have been clear all that it isnt always a major problem.  But, if you believe HeatGeek and the physics, in many cases it is, depending of course on the scale of the oversizing and the circumstances.  If the heat pump does not modulate sufficiently to deal with the shoulder season (where much of the heating actually occurs) or if the knock on effects cause unnecessary disruption and cost (which they certainly can do) then it is a major problem.   Also it is likely to make the difference between a single fan and a two fan model, which almost certainly means that express planning consent is required when otherwise it could be done under PD.  Express consent gives the LPA the opportunity to impose unachievable noise constraints.   

 

Brushing the issue under the carpet wont make it go away, knowing the actual figures will allow an intelligent choice to be made.  I know which I would prefer.

 

2 hours ago, billt said:

I think you need to look at it more closely.

 

Our house is a hotchpotch of additions carried out at different times with different construction methods and it is possible to model that in the heat punk calculator.

 

You can enter fabric losses for each element in each room separately as well as air changes for each room. It should come up with a pretty accurate heat loss figure

 

...if the surveyor bothers to take any notice of the additions then yes.  I had 2 full three hour surveys, told the surveyors more than once on each occasion about the fabric improvements, and they ignored any that they couldn't see.  Didn't someone on this forum tell us that they had learned a long time ago never to take any notice of what the customer tells them?

 

And even if the surveyor does take notice of the fabric improvements, that doesn't deal with the unknown ventilation loss.

 

Defending the current position is, IMHO, defending pseudo-science.  The science is sound but we simply don't, in many cases, have the required data and we also have human beings who choose to ignore it.  The impressive spreadsheets make it look scientific, but gigo still applies.  I'm NOT saying that the calculation is useless, just that there are, at least in a substantial number of retrofit situations, material factors which are either unknown or not easily verified to the extent that it should be treated with a healthy degree of suspicion. 

Edited May 25, 2023 by JamesPa

[JamesPa]

6 hours ago, SteamyTea said:

Write to your local MP, and the Energy Secretary.

And the BBC.

This nonsense has to be stopped.

At the right time I will.  The Planning department of my LPA are still digging even deeper (but at least clarifying their position), so I want to follow this to its conclusion.  Furthermore political control of the the LPA changed two weeks ago from Conservative to a Green/Lib Dem alliance, with the Greens in the majority.  It seems to me that the members might be rather interested in what is being done in their name.  I have already put out feelers and think I need to explore the new political levers before going national.  The local paper might also be effective, they wont want the headline that their newly acquired administration is anti-green!.

 

By way of update, the LPA have now confirmed that their requirement is to achieve a sound pressure of 25dB(A) at the assessment points (the PD requirement is 37dB(A)).  The one concession that they have made is to allow the calculation to be done using the MCS method, which at least, for now, avoids the requirement to call in an expensive consultant to prove how impractical their requirement.  I might just have a way to meet 27-28dB(A), but it requires the LPA to be reasonable in another respect which, based on behaviour to date, seems unlikely.  So I have a few more design what-ifs to do before coming to a final conclusion.

[billt]

I thought we were talking about sizing the system yourself? MCS surveyors not involved. Presumably you have a good idea of the construction of your house, in which case you can use the HeatPunk calculator to get a pretty accurate result. Obviously gigo applies, but if you're doing it yourself you would take care to put accurate values in.

 

 

This is a rough plan of our house. The room on the bottom left has solid brick walls with no insulation, a solid floor with no insulation and a pitched roof with no or very little insulation. Those elements can all be modeled in the HeatPunk calculator. You can create your own element if you need to. The room on the top left is the most recent and has 50mm insulation in the solid floor 75mm in the cavity walls and 200mm in the ceiling. The room on the bottom right has a suspended wooden floor, cavity walls with some blown in insulation and 200mm insulation in the ceiling. All the elements can be specified individually, there's no need to guess and use approximations.

 

The best thing about the software is the result page. You can choose a heat pump and play around with the flow temperature. It will show if the heat pump has enough output or not.

 

 

And it tells you if the emitters can reach each rooms design temperature at the specified flow temperature.

 

 

[JamesPa]

1 hour ago, billt said:

I thought we were talking about sizing the system yourself? MCS surveyors not involved. Presumably you have a good idea of the construction of your house, in which case you can use the HeatPunk calculator to get a pretty accurate result. Obviously gigo applies, but if you're doing it yourself you would take care to put accurate values in

Either really. 

 

If I size it myself using MCS assumptions but the correct fabric I get to 10.5kW.  Actual measured is 7.5kW based on last winter when it was, for 5 days, consistently below the local 'design' temperature of -2C.  A similar number is obtained by taking half hour smart meter readings and performing a regression against degree days.  I put the difference between my calculations and measured down largely to ventilation. 

 

Two MCS surveyors, following in each case a 3 hr survey, came up with 16kW.  The difference between this and my calculations is that they ignored the invisible fabric upgrades I told them about.

 

As stated above, Id like to go non-MCS to avoid the constraints, but this is currently blocked by my LPA.  And going MCS is blocked by their seeming insistence on fitting a 16kW pump to a 7.5kW house.  I'd be happy with 9kW or even 11.2, but not 16, which anyway will be dual fan and so wont get usable planning consent given that my LPA is currently demanding that I achieve 25dB(A) at the assessment point.  

 

Im actually interested in two things namely: 

 

1) finding a way to get a heat pump installed for my own house, currently snookered

2) attempting to challenge the industry to do better than it currently is doing, because if it continues as is the fossil fuel and hydrogen ready guys are laughing as a result of the inevitable headlines  in the Daily Mail and Telegraph about disastrous rip-off installs, which are already occurring on a regular basis.

Edited May 25, 2023 by JamesPa

[DanDee]

13 minutes ago, JamesPa said:

Either really. 

 

If I size it myself using MCS assumptions but the correct fabric I get to 10.5kW.  Actual measured is 7.5kW based on last winter when it was, for 5 days, consistently below the local 'design' temperature of -2C.  A similar number is obtained by taking half hour smart meter readings and performing a regression against degree days.  I put the difference between my calculations and measured down largely to ventilation. 

 

Two MCS surveyors, following in each case a 3 hr survey, came up with 16kW.  The difference between this and my calculations is that they ignored the invisible fabric upgrades I told them about.

 

As stated above, Id like to go non-MCS to avoid the constraints, but this is currently blocked by my LPA.  And going MCS is blocked by their seeming insistence on fitting a 16kW pump to a 7.5kW house.  I'd be happy with 9kW or even 11.2, but not 16, which anyway will be dual fan and so wont get usable planning consent given that my LPA is currently demanding that I achieve 25dB(A) at the assessment point.  

 

Im actually interested in two things namely: 

 

1) finding a way to get a heat pump installed for my own house, currently snookered

2) attempting to challenge the industry to do better than it currently is doing, because if it continues as is the fossil fuel and hydrogen ready guys are laughing as a result of the inevitable headlines  in the Daily Mail and Telegraph about disastrous rip-off installs, which are already occurring on a regular basis.

 

Place it in your attic and duct the air flow in/out(I mean do whatever it takes to achieve that if the attic exists and is free)

Place it outside in the least noticeable spot, and build/disguise it, duct air in/out, do you have a spot outside that it's not in the eye of any neighbour?

 

[Dillsue]

Place the mounting slab on casters so its "mobile"therefore temporary and nowt to do with planners

[JamesPa]

4 hours ago, Dillsue said:

Place the mounting slab on casters so its "mobile"therefore temporary and nowt to do with planners

That's actually quite a good one.  I guess they will argue that its plumbed in so is permanent though, but as the pipes and electric cable are flexible....

 

Its all getting very silly.  The LPA are now demanding that I achieve 25dB(A) whereas PD is 37dB(A).  They are completely ignoring the fact that, when its cold outside, people will be inside with the windows closed.  I cant imagine that 25dB(A) is achievable in more than a tiny fraction of homes, and certainly not with a monobloc because of the restrictions on pipe length.   

[SteamyTea]

1 hour ago, JamesPa said:

The LPA are now demanding that I achieve 25dB(A)

They are mental then.

I held my phone at arms length, the peaks in the middle is me breathing.

 

[RichardL]

 

5 hours ago, JamesPa said:

achieve 25dB(A)

Absolute or above ambient & at what distance from the box?

There's usually a distance?

Edited May 26, 2023 by RichardL

[JamesPa]

44 minutes ago, RichardL said:

 

Absolute or above ambient & at what distance from the box?

There's usually a distance?

Absolute, at the nearest noise sensitive assessment point (property).

 

The PD requirement is 37dB ditto.

Edited May 26, 2023 by JamesPa

[DougMLancs]

@JamesPa I notice Brendon Uys from Heacol has moved down to Bicester to set up Ultimate Renewables Supplies which includes the design and supply of heat pump systems as well as training up installers to his way of thinking. Their website is bare bones at the moment but some more info on their LinkedIn page. https://uk.linkedin.com/company/ultimate-renewables-supplies

I like Brendon’s innovative approach to system design (he’s designing our system) and now that he’s further South he might be of help in your situation?

[JamesPa]

2 hours ago, DougMLancs said:

@JamesPa I notice Brendon Uys from Heacol has moved down to Bicester to set up Ultimate Renewables Supplies which includes the design and supply of heat pump systems as well as training up installers to his way of thinking. Their website is bare bones at the moment but some more info on their LinkedIn page. https://uk.linkedin.com/company/ultimate-renewables-supplies

I like Brendon’s innovative approach to system design (he’s designing our system) and now that he’s further South he might be of help in your situation?

Thanks for the tip off.  He's not that close but I will make contact.  

 

[DanDee]

[JohnMo]

Novel solution... 

[JamesPa]

8 hours ago, JohnMo said:

Novel solution... 

I like it, until you need to service it!

[sharpener]

On 25/05/2023 at 19:41, billt said:

I thought we were talking about sizing the system yourself? MCS surveyors not involved. Presumably you have a good idea of the construction of your house, in which case you can use the HeatPunk calculator to get a pretty accurate result. Obviously gigo applies, but if you're doing it yourself you would take care to put accurate values in.

 

The best thing about the software is the result page. You can choose a heat pump and play around with the flow temperature. It will show if the heat pump has enough output or not.

 

 

Thanks for this suggestion @billt. Not quick but very comprehensive. Process not very well explained e.g. you have to click on an Options button to get to the flow temperature slider bit. Got there in the end!

 

Have now done a black box model of the whole house with correct external construction and rads but without any internal walls just to get overall heat loss. Result is as under. The worst case 48C flow is only required for the bedroom rads first thing in the morning and late at night when I will be wanting DWH at the same time anyway, it drops down to 43C during the day gving a SCoP of 4.31 which I would be quite happy with, and 16% spare capacity.

 

Three points of detail with the Heatpunk s/w which someone might be able to help with:

 

i) I had to choose K1 rads in the "Plans" stage to get them to appear correctly as K2 at the "Heat Pump" stage later on (and vice-versa), has anyone else encountered this problem?

ii) the CIBSE Table A figures from various sources for Plymouth are 99% -0.2C, 99.6% -1.6. (The MCS 3005 spec says the installer can choose which column to use, without giving any criteria for this.) But Heatpunk has used a figure of -1.3 which is not valid for anywhere in the table! The degree days for Plymouth are OTOH correct, 1858.

iii) Although it tells you whether you need to make a formal planning application on grounds of noise it does not seem to know about the 0.6m^3 size rule.

 

 

 

Meanwhile Veritherm have come back to me with a price of £905 + VAT, so I would have to be extremely confident the installers would pay attention to their findings before paying that much. Also they will shortly stop doing surveys for the summer because the nights are now too short and too warm for their technique to work properly.

 

 

Edited May 29, 2023 by sharpener

[DanDee]

On 28/05/2023 at 07:46, JamesPa said:

I like it, until you need to service it!

 

[JamesPa]

10 hours ago, sharpener said:

 

Thanks for this suggestion @billt. Not quick but very comprehensive. Process not very well explained e.g. you have to click on an Options button to get to the flow temperature slider bit. Got there in the end!

 

Have now done a black box model of the whole house with correct external construction and rads but without any internal walls just to get overall heat loss. Result is as under. The worst case 48C flow is only required for the bedroom rads first thing in the morning and late at night when I will be wanting DWH at the same time anyway, it drops down to 43C during the day gving a SCoP of 4.31 which I would be quite happy with, and 16% spare capacity.

 

Three points of detail with the Heatpunk s/w which someone might be able to help with:

 

i) I had to choose K1 rads in the "Plans" stage to get them to appear correctly as K2 at the "Heat Pump" stage later on (and vice-versa), has anyone else encountered this problem?

ii) the CIBSE Table A figures from various sources for Plymouth are 99% -0.2C, 99.6% -1.6. (The MCS 3005 spec says the installer can choose which column to use, without giving any criteria for this.) But Heatpunk has used a figure of -1.3 which is not valid for anywhere in the table! The degree days for Plymouth are OTOH correct, 1858.

iii) Although it tells you whether you need to make a formal planning application on grounds of noise it does not seem to know about the 0.6m^3 size rule.

 

 

 

Meanwhile Veritherm have come back to me with a price of £905 + VAT, so I would have to be extremely confident the installers would pay attention to their findings before paying that much. Also they will shortly stop doing surveys for the summer because the nights are now too short and too warm for their technique to work properly.

 

 

If you think you're going to need pp it might be worth putting in an enquiry with your LPA.  Mine is demanding 5dB below night time background (measured at the assessment point) which equates to 25dB(A).  That's impossible other than with a split halfway down the garden, which I haven't ruled out but it involves digging up 10 m of path.  None of the MCS bods took this into account, but their 16kW monobloc offerings (for my7.5kW house) would require express consent so were in fact all undeliverable within the law

 

Have you got actual meter readings for your house?

Edited May 30, 2023 by JamesPa

[sharpener]

8 minutes ago, JamesPa said:

Have you got actual meter readings for your house?

 

Of a sort, see upthread or maybe elsethread, average oil consumption during a very cold spell was about 6kW round the clock - but with extensive use of zoning. So I am confident that a Vaillant Arotherm +10kW HP would keep the entire house very comfortable - and probably using no more energy as several have previously suggested. Possible alternative is a Mitsi Ecodan 8.5.

 

And if I replace 4 rads but with K2s instead of P+s it would reduce the required flow temp to 45C and this just squeezes into the performance envelope of the Arotherm + 7kW which has 5dB lower noise power, is < 0.6m^3 and will run off a 16A breaker. Alternative is a Mitsi Ecodan 8.5 (but that is 3dB louder and needs 25A supply).

 

Either would leave something in hand because of

(a) the overspecified min. OAT (see above) and

(b) the model assumes it puts 850W into a rad in the kitchen to simulate the AGA, whereas this actually emits about 1.5kW

 

Another plus point for Vaillant is they have their own field engineers with vans full of goodies whereas all the other cos. pay the installers £90 for a diagnostic visit and then they have to come back again to fit the replacement parts. The main issue with them is that AFAIR there is no warranty (except presumably Sale of Goods Act or whatever) if not fitted by registered installer.

 

ATM am waiting for the two installers to get back to me before I decide whether to pursue either the Good Energy quote or the Veritherm one.

 

Sorry you have not had better joy with the planners @JamesPa, am keeping my fingers crossed about that. Have you investigated fitting an acoustic screen or enclosure? The MCS protocol gives a 10 dB allowance for that. I have also thought about putting noise absorption mat on the wall behind to make it 1 reflective surface rather than 2 which would give you another 3dB.

[JamesPa]

9 hours ago, sharpener said:

Of a sort, see upthread or maybe elsethread, average oil consumption during a very cold spell was about 6kW round the clock - but with extensive use of zoning. So I am confident that a Vaillant Arotherm +10kW HP would keep the entire house very comfortable - and probably using no more energy as several have previously suggested. Possible alternative is a Mitsi Ecodan 8.5.

It sounds like you are, in broad terms, where I am.  I now have sufficient confidence, from experiment and calculation, in the actual loss, so know what I want irrespective of the grant harvesters.  You seem to be in a similar place.  At least you cant now get ripped off for an unsuitable system.  If you do end up deferring till next year, I seriously suggest to run it like an ASHP and take lots of readings (easy with gas, you get half hourly meter readings!).

 

So for me its now 'just' a case of finding a way to do what I want, either with or without MCS.  Lies about internal wall insulation may help in my case (if anyone will take any notice at all of anything they are told but cant see) together with finding an installer who things out of the box or...

 

9 hours ago, sharpener said:

Sorry you have not had better joy with the planners @JamesPa, am keeping my fingers crossed about that. Have you investigated fitting an acoustic screen or enclosure? The MCS protocol gives a 10 dB allowance for that. I have also thought about putting noise absorption mat on the wall behind to make it 1 reflective surface rather than 2 which would give you another 3dB.

I have thought about barriers and/or enclosures.  Acoustic enclosures are ridiculously expensive.  In my preferred location a screen would look ridiculous, even my LPA agrees with that (even though they suggested it!).  There is another possible option, more expensive, but crucially it would only suit a split and few splits are available in this country.  I'm still working on technical, or political, options.  LPA may be starting to move a bit.  I've been in contact with the (Green Party) exec member in charge of planning and separately my (Tory) ward councillor.  I think that they genuinely see that something has to be done.  Protocol pretty much stops them getting too involved in individual cases but they are talking about using mine as 'an opportunity to learn lessons'.  Im not giving up!

 

 

[sharpener]

2 hours ago, JamesPa said:

If you do end up deferring till next year, I seriously suggest to run it like an ASHP and take lots of readings (easy with gas, you get half hourly meter readings!).

 

Unfortunately the lowest temperature I can set my oil boiler to is 65C, this is to prevent condensation from the acid flue gases. As it is also quite over-sized it will even so only run for about 15 mins in the hour so very unrepresentative of HP operation. Measuring oil consumption at frequent intervals is not easy as the tank and sight glass are in an outbuilding. I could I suppose measure the actual firing time with an hours run meter but I am not sure it would greatly improve on the measurements I have already taken.

,

2 hours ago, JamesPa said:

Acoustic enclosures are ridiculously expensive. 

 

In a former life I had a project on avionics which needed a 50Hz to 400Hz motor-generator set installed in the lab, which made a horrendous noise. So over one weekend I built a box round it out of 3/4 in chipboard lined with 50mm fibreglass, leaving staggered ventilation openings with no line of sight through.

 

On the Monday I told the fellow in the office next door what I had done and said I was about to start it up. In fact it had been running for half an hour and he had not noticed. I would guess the noise reduction was 25 or 30 dB so was well pleased.

 

IMO the main problem with doing this kind of thing on an outdoor HP is keeping the insulation dry. I recall however you can get special non-absorbent closed-cell foam from marine suppliers for soundproofing engine compartments which might do the trick. Would also work on the wall behind the unit as upthread. A canopy covered on the top with roofing felt and on the underside with acoustic absorbent would keep the rain off it and help to reduce the radiated noise even further. But as you say, not pretty.

 

Good luck with your multi-pronged attack on the planners. Have had my own run-ins with them but the partisan chairman of the LA lost his seat in the local elections so has now had his comeuppance.

[PeterW]

20 hours ago, sharpener said:

 

Another plus point for Vaillant is they have their own field engineers with vans full of goodies whereas all the other cos. pay the installers £90 for a diagnostic visit and then they have to come back again to fit the replacement parts.

they don’t have that many engineers and a lot are just rebadged gas fitters so you’re better off finding a local refrigeration company with most failures on ASHP being on the f-gas side and all Vaillant will do is plug it in and check the errors. 

[JamesPa]

16 hours ago, sharpener said:

I recall however you can get special non-absorbent closed-cell foam from marine suppliers for soundproofing engine compartments which might do the trick.

You can, I have some insulating the engine compartment of my narrow boat.  Unfortunately it's a thermal insulator as well as an absorber of sound.

[Carrerahill]

I won't read the whole thread, out of laziness, but, the way to size heating systems properly is to do heat loss calcs for the building, then size the emitters (usually with 10% margin) then size the source.

 

I have a spreadsheet which you key all the figures into and it spits out the heat loss, you key in your U values for walls, glazing, floor & ceiling, there is a column for infiltration and that's you. 

 

We are doing some 3 bed flats at the moment and the heat loss for the whole flat is 4.9kW. Therefore the ideal source would be about 5kW, yet in plenty of flats like this you will find a 20kW boiler (I understand the water generation argument there) but most sources are oversized.