JamesPa

I don't suppose this comes off? I have dismissed this unit precisely because of the fancy glass front. Otherwise it looks a good match to what I need assuming I eventually get over my planning hurdle.

MCS is currently consulting on amendments to MCS-020 which defines the noise standard for permitted development https://mcscertified.com/consultation-mcs-020-planning-standard-for-permitted-development-installations-of-air-source-heat-pumps/ They are putting forward a fair few sensible ideas and others which could be a nightmare. I attach my response in case anyone thinks it might be interesting. Obviously other may wish to respond directly to MCS with their own views. Incidentally MCS-020 is also the reason why installations must be done by an MCS contractor to MCS standards if Permitted Development is to apply. This is IMHO crazy - planning legislation is concerned with the external effect of development on others not the householder and the technical details of the installation (ie MCS standards/Installer) effects only the householder. Thus this belongs in Building Regulations, consumer law, or the rules for getting Government Grants, but not in not planning law. It should, IMHO, be removed leaving only the noise criterion to be defined in MCS-020. Response to MCS Consultation re MCS-020 - name redacted POST.pdf

As i understand it the harlequin is essentially a thermal store, which have Imited delivery capacity unless heated to a temp much higher than the delivery temp, so not a great match to a heat pump.

I think it is a good way to size a heat pump, but am cautious about relying on just 48 hrs only because houses respond quite slowly to changes in ambient and have a significant thermal mass. Thus any reading over that short a period is subject to considerable error. I find mine (1930 solid walls, suspended floors plus partial IWI and about 30% more modern extension) takes two or three days to fully stabilise in times when the outside air temperature is pretty constant, and when the OAT is varying wildly I doubt equilibrium is ever achieved. To put some numbers on it, there is evidence on another forum that the heat capacity of the fabric of a 3-4bedroom 150-200 sqm house is 10-20kW/deg C, which is significant in comparison the the heat loss. So any measurement needs to be done over enough time to take out fabric heat capacity effects. Having said that I suspect a 48hr reading is still better than the GIGO spreadsheet method and I would guess that its highly likely that (say) a week of half hourly meter readings with IAT and OAT and a suitable correlation engine would suffice. Still easily doable, as I have said several times on this forum I cant believe Octopus aren't already working on it, they have all the data and seem to like using it. For my money its smart meter readings first, consumption over a period second, and spreadsheets as a very poor third. Pity MCS (more or less) insist on exactly the opposite. On a positive note things do change. Two years ago, if you were to believe this forum and others, buffer tanks were 'necessary', now they are 'to be avoided unless absolutely needed'. 55C was an absolute no-no and now its actively being discussed. That just leaves two big 'practice' problems to crack namely: the GIGO spreadsheet and the insistence on replacing DHW tanks. I might also throw in the nonsense of the rigid application of the guidance (not the letter) of G3 if the only heat source is a heat pump, but @JohnMo will kill me if I do that!😊

I wouldn't trust a 48 hour gas meter reading there are too many dynamics in this. I would go either for the whole season (compare with degree-days) or a few weeks of smart meter readings. But if you have a smart meter why not the whole season? In most houses other than passive houses no real need to subtract the summer use. Unless you run a restaurant gas cooking use is negligible. As @JohnMo says there is no need to reinvent the wheel, the need is to convince the MCS bods to change the way they do things (or scrap MCS altogether).

Did the same with my boiler a couple of years ago, set FT to 55, works just fine, no plumes of steam from the flue and the house is much more comfortable. I suspect a fair few houses are like this. (In case you are wondering - my clueless, Green party run, local planning authority is blocking my installation of a heat pump - wants a sound level of 25dB(A)!)

I guess the reasoning was that 55 is good enough for a HP swap and guarantees condensing and to go any lower would result in push back from the industry/climate deniers/right wing press/party donors to the point where the rule risk being put on hold altogether. Politics is the art of the possible and 55 will do, its good enough that you can reasonably swap for a HP without upgrading the space heating. If you've designed for 55 the primaries must be large enough to operate at 55. Personally I think its an excellent compromise and much better than might have been expected given the direction of the prevailing wind.

Interesting. You would have thought, given this, that it would suffice to tell the heat pump a) the design flow temp b) the design OAT and c) whether it was dealing with rads or UFH (so it knows to use dt^1 (UFH) or dt^1.3 (rads)) all of which the installer should know. These three pieces of information are sufficient for the heat pump itself (or an app provided by the manufacturer or a third party) to work out a basic WC curve to start from, and then Auto Adaption takes over from there. Surely its not unreasonable to expect a plumber to program that basic information in, which they must have.

Interesting. Do we know how Mitsubishi Auto Adaption actually works. I can think of at least three options Use the WC curve as a starting point and 'tweak' but without long term learning Use the WC curve as a starting point and 'tweak' but with long term learning, so that it might eventually depart from the WC curve entirely Use nothing as a starting point and 'tweak' but with long term learning, ie work it all out from scratch I am pretty sure it must use a feedback loop with at least 2 time constants, a short term one and a long term one.

I have absolutely no clue. Whilst WC is pretty good, its unlikely, for many houses, to be good enough on its own and even if it is in principle good enough, to set it up sufficiently precisely is too much of an ask for the average person.

+1 (mostly). My personal view is that FT=55 (mandated now for new buildings even if they have gas boilers, and likely enough in many retrofits - eg mine - because rads are already oversized due to fabric improvements) will turn out to be the practical sweet spot for radiators. The ability to go to 65/70 will be used for DHW, likely with legionella cycle done by the Heat pump for simplicity - Vaillant already do this. A bit of adjustment of the relative prices of gas/electricity (which are politically driven anyway) will make this no less affordable than gas, and using a higher flow temp for DHW will eliminate the need, in many cases, to replace cylinders.* I don't however accept that weather compensation will go, I think it will stay but simplified and augmented by load compensation, so that it doesn't have to be too accurately to set up - and is thus easy. Several heat pump manufacturers already have this and of course this is exactly what Homely does. I did actually say more or less exactly what @HughF says about a year ago on this forum, but was shouted down by many at the time. *It may be necessary to retrofit a plate heat exchanger to improve recovery time, but that's cheap by comparison with total replacement. There is still the problem of persuading installers not to insist on cylinder replacements - because that's where they hide the mark up, but hopefully the market will eventually fix that.

I haven't heard of Podesta (a reference/link would be appreciated) but ... Precisely! External temps are actually known anyway from weather stations. You could probably come close to inferring internal temperature from the data (because you know both the change in consumption and the change in external temperature from which you can pretty much infer the actual internal temperature, but better I grant actually to measure it for a while). I cant believe that Octopus aren't already working on this as they have tons of smart meter data, know where the meters are, and have an interest in heat pumps, particularly small ones. Hopefully this will eventually put an end to the over-estimates that the spreadsheet jockeys tend to produce and with it at least some of the problems that heat pump deployments face because of poor design/installation. A bit of AI should be able to replace the (frequently absent) human intelligence fairly easily I would have thought. Edit - I found Podesta https://energy-surprises.blogspot.com/2022/06/how-big-should-your-heat-pump-be.html

Why does hardly anyone think to use meter readings? If current heating is gas, particularly if there is a smart meter, the heat loss is known pretty exactly if one just looks in the right place!

For what it's worth the actual measured heat loss in my 1930s house (albeit with some later extensions) can only be explained by assuming 0.5ach, which is frustrating because most of the MCS brigade insist on using 2-3. Double glazing without trickle vents, internal wall insulation, blocked chimneys and solid flooring downstairs is presumably sufficient to reduce the natural ventilation to this level. There are a couple of odd corners where mould is a problem (and where I plan to fit some extract), but by and large it's OK.

What were you expecting, whacking the flow temp up to max minimises the probability of another call out because its cold, which is the primary driver for many. You don't need to take that from me, several who are apparently in, or linked to, the trade have told us on this forum that minimising call-outs is a/the primary motive. I dont doubt that there are many who do not take this approach, but it appears that there are also many who do.

If buggering around with heat pumps were the only thing happening then of course not. But it isnt and change gains momentum unless too many luddites resist. As to building a wall, forget it as any kind of long term solution. You won't stop the forces of nature.

Er don't you think coastal cities or London flooding will be a direct hit on your living standards. Or storms which destroy houses and toss your car down the road, or mass migration due to displaced communities, or more likely war and starvation? You obviously feel very secure and certain that things will just carry on without materially affecting you. Unless you are a billionaire, you aren't secure and they won't.

It's a closed shop with rigid rules and carefully designed ways to exclude newcomers and stifle innovation There is a government subsidy And much of the market is retrofit, which is a different design skill that many installers (in part understandably) don't like, because it involves them taking risk and responsibility rather than painting by numbers. So we end up with poorly yet over engineered system designs replacing many unnecessary components causing more disruption than necessary and thus costing more, which is easily disguised in an unnecessary or unnecessarily extensive hot water system/pipework replacement/buffer tank or whatever, and the grant.

Or do both, ie deal with the inevitable and avert the even worse?

Er not quite a token gesture (led donestic lighting is the token gesture). Heating activities are about one third of uk carbon emissions and domestic is about half of this, nearly 20 percent. Giving up completely, which you appear to advocate, is somewhat defeatist don't you think? Is that really your view, forget it all and be damned? If so then at least please declare that upfront as its pointless discussing things which affect the future with someone who sees no hope

Mostly agreed, but who pays for governments - we do. As I say the option to pay or not to pay is long since gone. The only question left for the average person is whether to pay in a controlled way or through chaotic catastrophe. If you want the former rather than the latter, you need to advocate and support measures to combat climate change and support politicians who do likewise.

Sadly many people don't recognise the train crash heading in their direction until it's too late, and many politicians exploit this for their own ends. Fail to plan = plan to fail.

If it doesn't happen the costs will be vast, much more than the cost of fitting heat pumps. It's time we re focussed on to 'how are we going to make it happen' rather than trotting out lame excuses to avoid the inevitable. If we want to make it happen we surely can. For example I'm sure that many of the people who seek refuge in this country would easily be capable of doing this work, and would be glad for the opportunity. Many are, after all, highly intelligent and/or skilled.

Indeed so. What must be done is definitely do-able. Its only lack of political will and spurious arguments against that are stopping us.

We shouldn't be aiming IMHO to replace 'perfectly servicable' boilers'. Our aim should be that every boiler that is replaced for some reason (eg it's no longer 'perfectly servicable') and every new heating system, should be carbon friendly (ie, in the vast majority of cases, a heat pump). That's 1.6m heat pumps per year BTW, about 20 times the current rate of installation. If cost is the concern then consider the cost of not dealing with climate change. Unfortunately, in the real world, we are now well past the point where you (unless you are over 80 or otherwise have a short remaining life) and I, have the option not to pay, the only questions now left are whether to pay in a mildly controlled way or to pay catastrophically and chaotically, and how we choose to distribute the now unavoidable costs. Had we listened 30 years ago things might have been different, but we didn't so they aren't.