jack

Welcome Steven, good to have you aboard. It's best to keep questions to a single sub-forum, so I've hidden one of the cross-posts you did on the topic you're asking about and removed it from the introduction above. For others, here's a link to your question:

Not my experience. We run our tank at 50 degrees and there's no issue at all with the mixers, even as the tank draws down and the hot water temperature drops. They're Crosswater Mike, for reference. Actually, we have a cheap mixer set in the downstairs shower and it's fine too.

I meant think about installing both heat and smoke alarms, specifically in the plant room. I'm not sure whether either is compulsory, but it's a small price to pay for a bit of extra safety.

I'd rephrase this as "should not, but definitely don't rely on it". Rather than re-hash a discussion that's been had in detail elsewhere on BuildHub, I'd point people here (I think you may need to have made a certain number of posts to access this sub-forum): It was a large number of claimants over many years. Originally, HMRC said on the claim form that if there was any question over the completion date, the date on the completion certificate could be relied upon. They removed that language from the form perhaps 10 years ago. Over time, they tightened up their approach until the reached the point they were interpreting the word "completion" or "complete" (can't remember which) in the relevant act to mean that any activity that could be mapped to that word started the three month clock. This was despite the claim form itself plainly stating that the clock started when the completion certificate issued, unless the claimant chose to use different evidence of completion. The trigger they most commonly used was being placed on the valuation register, presumably because that's easily verifiable information and is prima facie evidence that the house was complete enough to be habitable. But there's at least one example (it's somewhere on the forum) of them finding a Google streetview image and concluding that the house looked finished several months before the claim was submitted. ^^^ Now we're talking ^^^ I put my claim in 5 years after we were put on the council tax valuation register (which was around the time we moved in). I have absolutely no idea why our claim was allowed without so much as a murmur when others were still being rejected at that time, even for people who'd moved in only a few months before making a claim. One factor appears to be whether there are are receipts for significant amounts dated shortly before the claim is made. HMRC has lost a number of cases at the appeals tribunal over the last few years. Unfortunately, since the tribunal is administrative rather than judicial, every decision stands by itself and cannot be used as precedent for future cases. They should tend towards a consistent outcome over time, but for the time being there's always a risk of a particular tribunal going against you. That happened to one claimant shortly after a couple of the cases that were most damning of HMRC's behaviour. @bob the builder 2, I don't think there's a simple answer to your question, but hopefully the answers so far will help you identify the likely risks.

From memory, it happened while they were filming, and you hear it in the background.

There's no need for a one-to-one correspondence between the falling outside temp and the flow temperature compensation. My flow temperature only increases by about 0.3 degrees per degree of (falling) outside temp change. You need to figure out what the appropriate gradient is for your house, which may need some experimentation. Maybe it's just how you've written this down, but this table isn't right. When it's -4 outside, you want 45 degree flow temp, and when it's 16 outside, you want 25 degree flow temp (ignoring, for the moment, my comment above about there not being a need for a one-to-one correspondence between the falling outside temps and the rising flow temps).

Welcome to BuildHub. Do you know the make and model of your MVHR unit?

But you disparaged people for panicking about the high usage they could see during cold snaps. I don't disagree with anything else you say. ASHPs are absolutely being missold, designed badly, installed shoddily, and commissioned poorly. More government funding is just going to bring in more cowboys, unfortunately.

I genuinely can't understand your relentless hostility towards smart meters. Literally all they do is tell people how much energy they're using. I've personally got a lot out of having one over the last few weeks. If someone seeing their usage is enough to panic them then surely it's better they know now than when the bill arrives? You know that there are people who are virtually unable to turn on their heating because bills are so high? It isn't because it's colder than usual, it's because our housing stock is shit, inflation generally is out of control, and we're paying 2+ times what we were paying for energy only a year or two ago. My unit rate went up by a factor of 2.5 when I came off my last deal.

Ha! 6 of the last 8 posts on the forum are ASHP questions. This long period of freezing weather is certainly testing a lot of installations. Mine's fine in terms of keeping the house warm and the DHW up to temp. With no heating upstairs, I get complaints if the floor temp is much below 21 degrees (concrete floors don't help), so possibly we're running things a little warmer than you. We do seem to be using an awful lot of electricity at the moment, but even with good insulation and airtightness, we live in an almost 300 m2 house, and this has been the coldest week I've seen in my 14 years living the area. We should certainly expect to be paying more than usual. If anything, this cold weather is showing me that I hadn't quite optimised the ASHP settings, so I'm just taking it as a learning experience.

@Orion331, I've closed this one off in favour of your other post, which got a reply first. Ideally, we don't want the same question being answered across different threads, as it can make them hard to follow.

Around my way (Hampshire/Surrey borders), the odd overnight sub-zero low isn't unusual, but I'd generally make a comment to the missus if -3 or -4 were forecast. This last week, overnight temps have consistently been in the -5 to -7 range, with daytime temps no higher than 3 degrees (and regularly lower - don't think it got above 1 yesterday). The average temperature for the whole week will almost certainly be well below zero, which is unheard of in the 14 years I've lived here. So yes, not an ideal week to assess anything other than perhaps worst-case figures!

First, my answer was to your comment that "What is probably needed is another communication standard to supersede all the others". Second, I disagree that a lack of built in protocols is the issue (or the primary issue). Even those units that have the required communication protocol built in still don't offer up all available parameters to the user, or a meaningful way to control them. The real issue is interfaces and a lack of understanding of how these units actually work. Look at all of the posts in the ASHP sub-forum over the last couple of weeks. How many of the problems involve installers and users of ASHPs not getting even basic commissioning settings correct? As an example, the installation manual that came with my unit is woefully short on detail (see my complaint earlier today about programming the timer), and I'm severely limited in my ability to control or change parameters remotely unless I want to retrofit an expensive communication box and sign up for cloud control.

Many of these units will have the capacity to communicate via the Modbus protocol, but manufacturers (perhaps unsurprisingly) don't like users being able to access/change too many parameters other than via the more advanced controllers that you can buy for an eye-watering premium.

Imagine if the funds spent on researching fusion over the last half a century had been spent on battery tech. The other issue with fusion is fuel: there's increasing concern that even if we were able to build fusion power plants at scale, generating the required fuel at the necessary scale is another serious problem that is barely even being thought about at the moment. Frustratingly, this issue has been known about for years, but almost nothing's been done about it.

While a curved surface does help with that, it's still quite a complex shape as a whole when you include the boxes that stick out from the arch. I remain unconvinced!

Ha. My air test guy did loads of MBC tests, so he wasn't that impressed with our result!

The guy I used was very experienced and had never seen anyone achieve an EPC of 100 before. To be fair, I think a lot of his work was with developers, so perhaps not that surprising he wasn't see much in the way of low-energy builds.

Wow, it sounds like you can do most if not all of what I'd like to be able to do with mine. I didn't get as far as looking at controls, to be fair. When I looked into Nibe 7-8 years ago, I'm not sure it was even possible to buy them retail, or if it way, they were way more expensive than the equivalent power Panasonic. They also didn't (at least on the published figures) perform as well. I'd certainly be thinking a lot harder about controls if I were buying today. I'll eventually get around to looking into whether the optional controllers from Panasonic offer better functionality than I can get with the one that was in the box.

It's certified though. I can't imagine the PassivHaus Institute certifying a house that didn't pass the standard. In this case, there's loads of glass AND an uninsulated masonry arch that makes up the vast bulk of the non-glass fabric.

To be fair, even if you'd had the required airtightness, it's extremely unlikely you'd have managed to get certification after the house was built. It's technically possible to start the PH certification process after building, but there's a huge amount of record-keeping required to prove that what was designed was actually built. For example, every junction would need to be thermally modelled at design stage, which you can do/show after the fact, but then a full photographic record of every junction is needed to show that what was designed was actually built. The only building I've heard of managing this feat in the UK was that amazing arched house that was on Grand Designs: I really don't know how they managed it tbh. The arch is exposed internally along most of its length, and I can't see how they managed to insulate it at all, let alone to the sort of value that would been needed to meet the Passivhaus energy consumption standard.

Yes, I've been doing some tweaking of this too. I'm getting very frustrated with the controller that came with my ASHP. Setting the timer is a hideous experience. For example, it isn't clear exactly how the timer periods work. You basically program in a series of events, each of which is either "on" or "off". For each "on" event, you select whether it's DHW or UFH. The "off" event doesn't refer to the mode. It isn't clear whether setting UFH "on" from midday say, then DHW "on" from 14:00, results in the DHW setting overriding the UFH setting (in which case a single "off" event is all that's required to end both programs), or the DHW setting "nesting" within the UFH setting (in which the first "off" ends the DHW setting and the ASHP returns to UFH until the next "off" trigger). I don't really have the time (okay, the patience!) to experiment with this but knowing the details would make a difference to how I program it.

Well mine's working fine, more or less! I do think it could work more efficiently. Ideally I'd like to be able to change the flow temperature based on time of day or a trigger, so I can turn the temperature up when there's off-peak or solar power available, and run it cooler when energy is expensive.

Keep posting. I think the BuildHub hive mind has solved most of the ASHP and UFH problems that have been posted over the last couple of weeks. I've never seen this sub-forum so busy. I think a lot of people are suddenly finding in this cold snap that their ASHPs perhaps haven't been installed or commissioned as well as they should have been.

Amazing numbers, especially given your location. Back of a fag packet calculations: 50 kWh at COP of 3 = 150 kWH total energy provided for heating 150/7 = ~21 kWh/day That's an average of less than a kW over that period, which even in a Passivhaus would be impressive. What temperature are you keeping your house at? What sort of weather have you had? We've been mostly very cloudy, so very little solar gain, meaning the ASHP has been working harder. You mentioned some supplemental heating with your diverter - do you think you had much from that? I don't know exactly what we're using for heating at the moment, but I do know that I've never seen a weekly electricity cost as high as last week's (admittedly we were doing loads of driving, so the electric car was the cause of a lot of those costs).