JamesPa

For the avoidance of doubt and offence by 'we' I meant society, not the trade. And your analysis about society's views is entirely fair IMHO. Unfortunately we seem to value air-head celebrities more than people with brains who can actually get important things done. Surely one cant expect anything else? Installers are businesses. As soon as you have to "come back" your profit from the job starts evaporating. Its also, invariably, unplanned, so causes great disruption to your other work. Thats also fair. It doesnt mean we should give up however. What we should do is recognise that installers wont want to come back, and design systems/processes/simple instructions so they can avoid doing so without materially compromising performance. Installers need to collaborate with this (because they are at the sharp end and have the fullest customer experience) for the good of their own reputation and society, but shouldnt necessarily be expected to lead it.

Please read my paper: it explores exactly this. https://www.mdpi.com/2071-1050/16/11/4710 Demanding overly tight temperature control WILL waste a lot of energy. If running pure weather comp as I am the flow temperature is only determined by external temperature. I will read your paper with interest but the summary you give above is absolutely no surprise to me. I too am running on pure wc and find it very comfortable. I don't yet have the data to prove definitely its cost effective but have every reason to believe it is. However I'm not sure how your summary above relates to my comment which is about how best to achieve desired temperature differentials between rooms while simultaneously minimising energy input, without any mention of tight temperature control.

I suspect the truth is a bit more subtle. If you don't heat a room at all it still gets fairly warm in most houses because of gain from adjacent rooms. As a result the emitters in adjacent rooms have to emit more than they otherwise would, which means you have to raise the flow temperature thus reducing efficiency. If instead you were to heat the room to somewhere around the temperature it gets to if you don't heat it at all, you will be able to drop the flow temperature. The total loss from the house will be the same, but as its supplied at a lower ft the heat pump will require less input energy. Ideally the heating of the unused room should still be low and slow, ie continuous drip feed not on off by trv. Adjusting the lsv is the conventional way to do this but a trv that responds very slowly and never shuts off would be better. I don't know if these exist yet or indeed whether opentrv does this. Its obviously possible in principle and has the potential to simplify or completely automate radiator balancing. It was a good suggestion. I suspect that, if they consulted the industry at all, they would have received a negative reaction along the lines of "encouraging homeowners to adjust the controls on gas boilers is dangerous". Of course the danger is that installers get more callouts, but so far as I can tell almost the entirity of design and installation practice both then and now puts this above all else.

It sounds to me like your WC curve may be set too high. If (a) you are stifling at night even with a setback, and (b) your TRVs are having any material effect during the day, then the most likely reason is that the flow temp is quite a lot higher than it needs to be. Are you certain that you have adjusted the WC curve correctly (ie as low as it can go consistent with heating the house to the desired temp)?

Clearly comfort is a matter of personal perception however the comfort benefits that were being discussed are the ones from low temperature operation(enabled essentially by weather compensation), not from continuous operation. They are different both in perception and effect on consumption/cost. Low temperature operation causes fewer short term variations in temperature (timescale 1-3 hrs), because the output to the emitters is matched to loss, and reduced spatial gradients. Many people will perceive this as more comfortable. That's entirely different to varying the target temperature during the day/night to suit different use patterns (eg night time setback for better sleep). Open fires in farmhouses are a rather special case, people do indeed like congregating near fires where the immediately surrounding air is heated to probably 25C plus, albeit that its possible to cool off by moving away. However thats not a common arrangement in modern houses! Incidentally low temperature operation is not just a feature of heat pumps, condensing boilers are (frequently) capable of it too and generally are more efficient if operated this way. Unfortunately our largely clueless heating industry hasn't bothered to implement it unlike some EU countries where weather compensation has been mandatory since the early 2000s.

Less temp swings - fabric of the building and furniture/furnishings all get to the same temp - don't need as high a target temp to feel comfortable because there aren't any cooler periods Exactly that. You can't achieve this with 'high temperature' heating because it has to switch on and off to match the heat loss of the house and places near the radiator are much hotter than elsewhere.

Sadly I believe you are right. Yet much of our political class and media argue relentlessly for deregulation without ever contemplating, it seems, that a 'free market' might not always act in the consumer interest!

A good option if you have the skills. I don't, so for the time to learn and then do it, £2k seems a fair labour price. For what it's worth I just had my ashp (retrofit) install done. Four rad upgrades, a new UVC connected to existing plumbing, and of course the ashp itself. It was literally a one person install (elec circuit was pre-installed) and it took him six days total, averaging at least eight hours per day. I watched him throughout and he barely stopped, and generally worked pretty efficiently. Admittedly he spent quite some time on leaky joints between new and existing plumbing, but in fairness that happens. I wouldn't do that job for £2k (neither did he, total price 12.5K less BUS!) given that he has to spend time in addition getting work, buying stuff, doing accounts etc. Obviously if it's a totally new build many of the miscellaneous embuggerations vanish, but the potential for time to disappear perhaps shouldn't be underestimated.

If my own house is anything like typical there is another advantage of operating low and slow, namely comfort. I have moved progressively from a boiler at 70C to (the same) boiler at 50, to an ashp with weather compensation at 30-45. Each gave a significant step change, for the better, in comfort. The reduction in temperature gradients in both time and space makes a material difference. The UK has been missed out on the advantages of low temperature, weather compensated heating for 20 years, other countries (in the EU) are more advanced. How come we were so stupid?

Depends on the rating (and derating characteristics) of the cable and the demand of the heat pump (or other load on the cable(s)). Sparky should be able to advise the former and the spec of the heat pump (or other loads) the latter. Don't forget to consider temp during legionella cycle if the heat pump does that natively (some do, some just switch on the immersion heater). I would definitely want to be certain its OK before going ahead, you really don't want smouldering cable on the coldest day of the year (which is when it will get hottest) causing a fire or taking your heating out! If its not OK would it be more sensible to reroute the cable rather than the pipework - cable routing is more flexible in all sorts of ways!

Interestingly this is pretty much what Vaillant implements, albeit with a touch screen either wirelessly (but independent of the internet) or physically connected. The way they have done it has the effect, IMHO, of making WC accessible to the ordinary person. You think you are turning the room temperature up and down, which you are, but actually by adjusting the WC curve. Others may of course do similar but it seems to me to be a major advance on the basic 4 point adjustment some machines feature.

I agree with this view (I too love tinkering etc). Complex stuff that nobody else understands is fine if its not 'mission critical' - heating is definitely mission critical to a house. Therefore the least techy person in the house needs to be able to operate it and the local plumber, or at worst the authorised agent, must be able to fix it. There is nothing wrong with add-on complexity for monitoring, but having basic functionality which relies on such complexity is inviting problems IMHO. To my mind these considerations come close to ruling out hybrid systems altogether, although a hybrid where the boiler is controlled by the heat pump controller is probably OK or @JohnMo s suggestion (but with some notes left for a repairer in an accessible and visible place (eg taped to the boiler and heat pump) so they know how its intended to work - which otherwise may not be obvious). At a much less mission critical level, we rip all our music to a NAS so we can enjoy it from several places in the house and control it with various devices. My wife can operate this (and loves it) but she couldn't maintain it. We therefore keep the CDs and a CD player so that there is a fallback should the NAS (or more likely me) become unavailable (it also serves to prove we have the rights to use the music under copyright law). Obviously its all a personal choice but perhaps one that should be made thinking of the others in the household.

I think so if it makes a material difference. The key points of MIS 3005 D are that it requires a heat loss calculation to be done with specified minimum interior temperatures, exterior temperatures dependent on location, and 'otherwise complying with BSEN12831-1:2017' Without referring to the latter I don't know what it says, but it would be surprising if it doesn't allow some latitude for accounting for the actual building. Unfortunately its £460 to buy. I doubt many if any installers actually have a copy so they will most likely be relying on interpretations/software produced by others. Thus they may be (and in my experience are) open to persuasion or may dig their heels in, depending on how confident they are in their own abilities/judgement. In the end they know that the MCS rules, followed to the letter, are their protection because following makes them essentially bomb proof. However the better ones also know that pleasing the customer and doing the right thing, with an appropriate interpretation of the MCS rules, is a better way, in most cases, to gain a good reputation.

I don't have MVHR, I have a 1930s house with (originally) solid walls, that has been subjected to various fabric upgrades at various times including double glazed windows that have no trickle vents and solid flooring downstairs. MCS ACH = 1.5-2.5 based on age. I ended up with two installers that provided satisfactory quotes. One assumed ACH = 0.5, the other a bit higher (0.8 I think). 0.5 gives a total loss that is consistent with the measured loss (based on analysis of half hourly gas consumption over 2 years), 0.8 ACH works out a bit higher than the measured heat loss, but still resulting in the same design choice of Heat Pump. I understand that decent MVHR has a recovery rate of 80% so I cant see why one would assume an ACH above (say) 0.25 unless its expressly mandated, specifically for heat loss calculations (which is what they are supposed to do) in the British Standard (to which I don't have access) referenced in MIS 3005-D.

From my personal experience it seems that the MCS 'rules' are interpreted with differing degrees of latitude by different installers. Sizing my own installation turned on: allowing for fabric upgrades which I know have been done (because I did them) but were not visible - some installers would and some point blank refused. This made a difference of 4kW assuming an ACH value substantially lower than the default - again some installers would and some point blank refused - this made a difference, on top of the above, of 3.5kW If your installer wont factor in something that matters, my advice is to find an installer that will. The actual text of MIS3005-D, the governing document - which is worth reading, is very much open to flexible interpretation. Following it to the letter and refusing any interpretation that the 'letter' leaves open probably gives maximum protection for the installer, which may not what you, as the customer, wants!

fair point, particularly given my experience referred to above with my gas boiler, albeit down to my stupidity!

Two because the two circuits are totally separate. The reason for the one on the primary circuit is to prevent overpressure due for example to forgetting to turn off the filling loop properly. I actually did that with my old boiler (where the PRV was) isolated. It blew a radiator quite spectacularly, fortunately it didn't blow anything under the floor otherwise it would have been an expensive mistake. If your mains pressure is low then its perhaps less important although a fault in the immersion could conceivably cause boiling in the primary (through heat transfer to coil) so there is (just) a way to get overpressure even with low mains water pressure, albeit very unlikely. If there is one in the heat pump then I cant see you need another.

Indeed. The Ideal R32 range looks suspiciously like Mitsubishi pumps to me, albeit with Ideals own control system. The physical dimensions are a perfect match.

I thought that their R290 products are rebadged Midea, at least thats what the people at Adia told me. I (and they) could be wrong of course! Otherwise agree with everything you say above, check EON tariffs as well as Octopus if you have an EV (and possibly if you dont).

Interesting discussion. Having recently got my heat pump installed, and possessing an EV charged from a 13A socket only, I am in the process of moving from Octopus to EON Next which gives 7 hrs at 6.7p/kWh without any requirement to have a dedicated charger. I don't do that many miles but the negative comments about OVO influenced me away from them and my calculations suggest EON works out cheaper than Cosy or OVO, in the latter case at least in part because of their poor export tarrif. Its also a lot less faff having a block of cheap electricity rather than 3 blocks. If anyone has any tips for 'getting on with' EON I would be grateful, otherwise I will report back in a few weeks.

My 15 year old Worcester Bosch (presumably now in the skip) actually had a WC add on available (I don't and didn't have it). Totally analogue so far as I can tell from the limited information now available!

There are clearly some 'perception' factors at work (we experience the same) which control systems ignore. I do wonder if humidity is one factor at work. If we do some washing and dry it indoors, even though we put the dehumidifier on and the measured house temperature is the same, it feels colder!

Noted. I think its WC that is the game changer in terms of stability, a technology thats been around for decades and is mandatory in some countries. It seems illogical to some, given that its room temperature that matters, but of course its perfectly logical because it means that the control system is ahead of the game rather than always playing catch up and the emitter temperature and hence output is more closely matched to the demand. Its something of an indictment of our heating industry that the technology was shunned in the UK until heat pumps forced it to happen!

For what it's worth my ashp was finally fitted a fortnight ago following a two year long and very painful planning saga. Installer set it up in a mode combining wc and control based on room temperature, all using the heat pumps own system controller with no external controls. After the first week I disabled the room temperature element of the control, and now have it set up on wc only, trvs fully open with heads unscrewed so they can have no effect. The result so far, in my house and with my pump, is a more stable house temperature than with the mode in which the installer left it, and much, much more stable than was ever achieved with my gas boiler operating at fixed flow temp with a thermostat and trvs. I have rads, not ufh with a massive slab BTW. Obviously this is one case only, however its doing what the theory says (and what should be the most cost effective), so it's not really a surprise. I would suggest that those who are sceptical of wc might wish actually to experience it if they haven't already!

Thanks. I was coming to that conclusion myself (and its the general approach I have been preaching for some time - get the WC curve right before you anything more sophisticated). My installer is back today to fit two rads that weren't available when he did the main job last week. I don't want to touch too much while he is still around, but once he is gone I consider it to be open season! That said, I can see why he has set it up the way he has. Most wont bother with or understand the tweaking of WC curves and the way he has set it up will get somewhere close eventually I think, without human intervention.