JamesPa

I fear that pure load comp wouldn't work very well because the response is too delayed. Clearly one of the big problems with any space heating control is the delayed reaction of the house to both external stimuli (eg OAT changing) and internal stimuli (eg turning the heating up). I'm not a control theory expert, but I do know that any delay in a control loop, particularly if you have disturbing and unpredictable features like solar gain, makes the design more challenging. WC attempts to get ahead of that a bit by measuring the external temperature and adjusting the flow temperature, possibly before the house itself reacts, to counter the energy loss from the fabric which is bound to happen. I suspect that's why the more advanced heat pumps use a combination of weather compensation (to get a basic setting) and load compensation (to 'tweak' it a bit).

It's a reasonable question. I think that getting the feedback loop to work stably, given the long response time of a house and the disturbing variables, is probably quite a challenge, but nothing a bit of electronics couldn't sort out over a period of a few weeks or certainly a season, as I understand Homely does. I suspect also that too many heat pumps are directly descended from aircon at present with not enough market specific development, although given that its exactly the same problem as for a fossil fuel boiler, you might have thought the manufacturers who also manufacture boilers would have it sorted. Perhaps German plumbers (and plumbers in other countries where its mandatory on boilers) are adept at tuning wc so there isn't much of a market. Its probably only since about the year 2000 that the technology to automate it became sufficiently cheap that it might be considered, and if by then plumbers had worked out how to tune it manually (which is very likely) the manufacturers would have little incentive to undertake a quite expensive development until it is adopted by backward countries like the UK. Perhaps they still reason that, if the Germans can do it, then so can anyone else.

Id suggest we are as a collective of installers. Of course there are a lot of very good capable insallers, but overall, no. The german approch to things is just different. Mostly in a good way. Oh dear, how sad. Well we have to swap gas boilers for heat pumps, so we will just have to work it out or else the uk consumer will be paying 15-25pc more for heating than they need to. Perhaps a 'collective of installers' could visit Germany!

Isn't that pretty much what Homely and the 'adaptive' control strategies which are can optionally be enabled on some heat pumps do. We don't know exactly what algorithm they apply, but as I understand them the idea is to take a basic/default weather compensation curve and slowly but surely tweak it to suit the house. Of course this still depends somewhat on a tolerable balancing of the emitters (and not fiddling with them at least for a while) but the industry has (supposedly) been doing that for decades (or has it?). Either way its not that difficult and, as I observe upthread, the Germans have had WC for years, and we surely aren't claiming to be less capable than they are.

Weather compensation has been mandatory in Germany for many years, which is why many newer gas boilers have it. Presumably German plumbers have found a way either to set it up in one go, return efficiently to tweak it, perhaps on a rota, or teach German house owners how to tweak it. Are we saying that our plumbers are incapable of doing what the Germans do? Presumably also Polish plumbers, who doubtless work just across the border from time to time now they have fled the UK, have also worked out how to do it. Alternatively we can just sacrifice 10-25% in performance. Given that replacing our gas boilers with heat pumps is now an unavoidable necessity, we are either going to have to sort it out or suffer a performance penalty. As it happens I am firmly of the opinion that, at least for homes with smart meters, a bit of AI (or even human intelligence) applied to the half hourly meter readings will both enable us to size heat pumps correctly (unlike the spreadsheet method as it appears to be applied in many cases) and create a weather compensation curve. I find it impossible to believe that Octopus aren't working on this already.

I agree but...It could still be more than 25dB(A) at the neighbouring property, which is the standard my LPA expect me to meet. If only gas and oil boilers were this quiet!

I read the whole report a couple of days before I saw the Telegraph article. My instant reaction to the Telegraph headline was that it took a warped (or determined) mind to come up with the headline given the actual content of the report.

Interesting indeed. Here is the latest DENZ report. Basically it appears to be an assembly of opinions with not a lot of analysis. However I suspect its more likely to be listened to than a third party report. https://www.gov.uk/government/publications/air-source-heat-pump-noise-emissions-planning-guidance-and-regulations

I think an architect could slightly modify this and declare it beautiful. Repeated patterns are a common theme in architecture and the natural world. It just needs a bit more symmetry and consistency.

To be frank I think it's unlikely the government will deal with it as the same comments apply to oil and gas boilers, and its a general rule that a planning consent does not immunise against a claim for nuisance). Also the law on nuisance has its origins in long standing common law and I have a hunch that its unlikely Parliament would want to interfere. I fear it needs a few cases to go to court to establish the law. Sadly I suspect not many would appeal an enforcement notice issued by a local authority so it may be some time before that happens (maybe your acoustic consultant has some info). Incidentally the pd level is 37dBA not 42. 42 includes (for some wholly inexplicable reason) a nominal background of 40dBA but the heat pump alone must meet 38dBA. I presume your acoustic consultant must know this. There is a long discussion on the matter here: https://renewableheatinghub.co.uk/forums/postid/16949 Finally here is the definition of nuisance from the EHO at my local authority (there is more from him if you follow the link) "For the noise to be considered a statutory nuisance it must do one of the following: unreasonably and substantially interfere with the use or enjoyment of a home or other premises injure health or be likely to injure health" I wonder how likely is it in practice that a judge would find this to be the case with a reasonably installed domestic heating system? Its a tough call to say that it's unreasonable to heat your home provided you have made some effort to mitigate noise.

It's completely daft. My lpa wants me to achieve 27dBA (it's starting point was 10dBA below background which it claims is 30dBA, I've talked them up a bit!). That's just mad.

Precisely and not a clue respectively! If you use the MCS official spreadsheet it's 37dBA so far as I can tell.

If 35/38dBA is the heat pump only (ie it excludes contribution from background) then it's very close or even above pd which is actually 37 dBA excluding background, or 38dBA depending on exactly how you do the calculations. 42dBA is often quoted as the PD value but this is wholly misleading as it includes an assumed background of 40dBA (why I don't know, the extra calculation steps merely serve to confuse).

If you think about it, most of the products that energy retailers sell are made in the software of the billing system. They don't manufacture energy, and they don't deliver it, all they do is buy it and sell it on without ever touching it. I'm fairness to Octopus they do manufacture and install heat pumps, but their main business is essentially software.

I'm not sure I would agree with this approach. The problem is that, if someone does complain and you don't have planning consent (whether express or under pd), then you haven't got a leg to stand on and, even though you may not be causing a nuisance, your local authority will use planning law as a lever against you to deal with the complaint (because its relatively straightforward whereas dealing with it under nuisance legislation is much more difficult). So unless you are pretty confident that there will be no complaint or know what you would do if there were one, I'd ensure you have planning consent (express or under pd as appropriate).

I spent quite a while looking for a ready made (or easy to make) solution to this one and failed. So I ran a wire. It was a bit if a pain but by going outdoors and through the loft no floors or walls were disturbed.

As a matter of interest what noise criterion is your planning authority insisting you meet. I have an ongoing argument with mine over their wholly unreasonable requirement if express consent is sought, and I think they now recognise that they have a problem because they have advised me to find a way to install under pd if at all possible (even though they will not accept pd noise levels, or anything close to them, when determining an application for express consent).

I think @sharpenermay be referring to this thread about noise in another forum. https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/noise-planning-expert It does discuss some of the issues encountered in depth, based around the experience of someone apparently facing enforcement action under nuisance law. Unfortunately the individual in question is definitely in violation of planning regulations and the local authority are probably using this to conflate the two entirely separate branches of law in a way which is not entirely helpful. I will shortly be posting on the same thread the best statement I can get out if my eho on the criteria for noise nuisance. Its sort of helpful, and sort of useless.

Strange. I was aware of the Vaillant backup heater (is it just a very expensive Willis heater in a box I wonder) but in nearly 80 pages of system diagrams https://www.vaillant.co.uk/downloads/aproducts/renewables-1/arotherm-plus/arotherm-plus-1/quick-guides/all-schematics-wiring-notes-1799366-2626556.pdf not one (so far as I can see) shows any electrical connection between the heat pump interface board and immersion heater. So its presumably a function of the interface unit/controller which they don't consider an essential part of the system? My (putative) installer has confirmed that the Vaillant 290 does the legionella cycle natively (ie without the immersion - which given that it can get to a FT of 75 is entirely believable and the heat pump manual appears to confirm) but of course that doesn't mean that it might not be capable of controlling an immersion. Prior to R290 the use of the immersion heater for legionella control would presumably have been necessary, and they probably haven't changed the interface board/controller. I cant see how a 'limp home' mode based on an in-tank immersion works for both CH and DHW if there is a diverter valve, unless the diverter valve itself has a 'limp home' setting or a bypass! My thought was to omit/ignore the immersion heater from the tank, and then a 'backup heater' inline with the heat pump can serve as a limp home both for DHW and CH, as well as a booster for exceptionally cold weather (of course the first of these depends on whether the water pump continues to work in heat pump failure mode). Currently this is more of a 'thought experiment' than an actual plan, because its convenient to have a wholly separate immersion to feed excess solar into (subject to the usual discussion about what the optimum strategy is for summertime excess solar/heat pump/immersion). However doing this would become very attractive if, by omitting the in-tank immersion heater altogether, and putting suitable protective measures around the Willis heater/heat pump combo, the need for a vent to the UVC is avoided. There is also something rather satisfying about having one component perform several functions, and having all of the heating elements of the system in one place feeding one set of plumbing.

Indeed. My gas boiler features two separate flow temperatures for Ch and dhw, but only if you fit their overpriced diverter valve (it occurs to me that it may be possible to fool it into thinking their valve is fitted). And a friend of mine has rigged up a circuit to fool his weather compensating boiler that it's -2 outside when it's heating dhw, to force it to max flow temp (the friend in question wasn't prepared to pay the extortionate amount the boiler manufacturer wanted for a diverter valve).

I certainly wouldn't disagree with that! Nor would I disagree with following the manufacturer instructions of any equipment used (at least in most cases, I am sure there are exceptions although probably relatively few, if any, related to UVCs supplied with internal immersion heaters). Having said that I still suspect (as others do including, I would imagine, you) that the problem OP has highlighted is basically due to a wrong valve (3 way instead of diverter). PS: my thoughts on 'But your real argument is about the need for venting to drain, as you have mentioned several times on other threads.' are now mostly related to circumstances where there is no immersion heater in the tank. For example the Vaillant R290 Heat pumps don't rely at all on a tank immersion, and SOFAIK aren't even capable of controlling one. As R290 becomes more common I imagine that this may be replicated by other manufacturers. In this case there is a possibility that one could install a tank, supplied by a heat pump, without an immersion, a situation which is rarely if ever considered. It seems to me that there are some interesting possible variants associated with this.

I could, but the preamble to the document says "If guidance in an Approved Document is followed there will be a presumption of compliance with the requirement(s) covered by the guidance. However, this presumption is not conclusive, so simply following guidance does not guarantee compliance in an individual case. It is also important to note that there may well be other ways of achieving compliance with the requirements. There is therefore no obligation to adopt any particular solution contained in this Approved Document if you would prefer to meet the relevant requirement in some other way. However, persons intending to carry out building work should always check with their Building Control Body (BCB), either the local authority or an Approved Inspector, that their proposals comply with Building Regulations." This makes it clear a) that the guidance is just that, it is a way (probably) to comply (note that it doesn't guarantee compliance) but not necessarily the only way. Given that it doesn't guarantee compliance there is still an implied requirement actually to think about the system. Also the guidance includes the following at 3.17: 'The selection of safety devices should take account of the physical location of the devices, and the design, configuration, location of components and performance characteristics of the system to which they are attached'. Of course I concede that following the guidance is the sensible route in the vast majority of cases, but slavishly following it may not be, given that it does not guarantee compliance. I also concede that whatever PL plumbers have may include terms which insist that the guidance be slavishly followed! My point nevertheless is that the actual rules do not need to change. The industry may need to wake up to changes in technology (and perhaps, persuade the Sec of State to extend the guidance), but (this part of) the building regulations themselves are (extraordinarily) well written in a way which does not inhibit innovation nor lead to a situation where people can say 'I was only following the rules' as an excuse for poor practice.

Can't see why the rules need to change, they are written in a way that allows sensible interpretation in almost any circumstance: G3. (1) There must be a suitable installation for the provision of heated wholesome water or heated softened wholesome water to: (a) any washbasin or bidet provided in or adjacent to a room containing a sanitary convenience; (b) any washbasin, bidet, fixed bath and shower in a bathroom; and (c) any sink provided in any area where food is prepare (2) A hot water system, including any cistern or other vessel that supplies water to or receives expansion water from a hot water system, shall be designed, constructed and installed so as to resist the effects of temperature and pressure that may occur either in normal use or in the event of such malfunctions as may reasonably be anticipated, and must be adequately supported. (3) A hot water system that has a hot water storage vessel shall incorporate precautions to: (a) prevent the temperature of the water stored in the vessel at any time exceeding 100˚C; and (b) ensure that any discharge from safety devices is safely conveyed to where it is visible but will not cause a danger to persons in or about the building.

As I said, surely academic unless there is a backup heater.

Surely this is a bit academic when the heat source being switched by the valve is a heat pump, which is incapable of boiling the water ... unless of course there is a 'backup' heater fitted as well inline with the heat pump