jack

Wow, strong first post!

Welcome to BuildHub!

Hopefully most people no longer suggest that a PassivHaus doesn't need heating. It certainly needs less heating, for less of the time. When it's very cold outside (near or below zero) for long periods, the weather compensation means that our floor does feel slightly warm underfoot. It's nothing like the warm/hot feeling you get underfoot with UFH in a house with less insulation, but I find that sort of heat very uncomfortable. It's also important to understand that a house with PassivHaus class insulation and airtightness is not necessarily a PassivHaus. While our insulation and airtightness are PassiveHaus class, I suspect that we wouldn't meet the full formal specification. The shape of the house isn't ideal. We have a lot of glazing in places and several north-facing windows probably need to be a lot smaller. I therefore find that our heating comes on earlier than many others with similar levels of insulation and airtightness. That said, we use less energy to heat this 290 m2 house than we did to heat the 90 m2 bungalow it replaced, and we're a lot more comfortable, so I'm not complaining! I'm sure you've spotted this in your research, but zoning generally isn't needed in a PassivHaus class house. Most on BuildHub with that sort of insulation run their entire downstairs slab as a single zone with a single thermostat. Some temperature variation can be achieved in different rooms with UFH pipe spacing, with fine tuning done by manually adjusting flows at the manifold (no need for electronic controls).

The guys who did our build used one of those. Super fast, easier to use over a wide area without having to move around so much, and waaay less stress on the wrists.

I was whizzing through this on my phone when I answered and didn't realise three of them were affected, or that they'd used the wrong fixings. A one-off might be unlucky, but three suggests a pattern. No way I'd be happy just repairing the cracked stuff - the fixings need to be done properly. Can they not go back and add fixings at this stage? Leave the ones currently in place and put the correct ones in the gaps between them. These are what was specified (and used) on our house. I don't like the idea of shot-fired fixtures into concrete that has shown a propensity to crack, so perhaps you could have a word with your SE about using something like this instead? As others have said, it's the SE who needs to be your guide here. The builder is reponsible for rectifying the fixings.

Epoxy repair mortar isn't that expensive and might work here (although maybe check with the tech department of whichever brand you buy to make sure it's suitable). Not sure who's responsible - I can imagine both sides blaming the other. I'd be tempted to just crack on rather than worrying about blame.

My inlet filter can look very dark after a few months, and we have no houses near enough to us for that to be soot.

Intros aren't required, but are appreciated! Find the right sub-forum(s) for the particular damp issues you're facing and ask away.

Awesome work again @nod Your numbers are always amazing. I realise a lot of that is because of your trade contacts and experience, but I also know that you and your wife are insanely hardworking people, so kudos to you. Do you have one or two pieces of advice to people who've started (or are considering) a selfbuild and would like to keep costs under control, especially for those of us without trade contacts and experience? I can't remember whether it was you, but I remember one person saying that when they found someone whose work really impressed them, they asked them for recommendations for other trades.

That's a good idea. A lot of members don't look at the Introduce Yourself sub-forum, so you'll generally get more and better advice if you post in the right sub-forum.

Welcome to BuildHub, that looks like an interesting project.

Welcome! I wouldn't worry about getting things wrong. Most of us aren't in the building trade, and even those who are started knowing nothing. Post a pic, use your own words (all in the correct sub-forum of course!) and you'll generally get the help you need.

Yeah, with the full spec sheet, it's easy enough to find the right bearing from whatever manufacturer. From what I've read, it's worth spending a bit more on SKF branded bearings (still only a tenner a pair - enough for a single motor).

Sure, MVHR manufacturers see it that way. But many MVHR units (at least those from Brink and Paul) use similar EBM Pabst motors that are certainly serviceable based on the many reports of people replacing bearings in them. I don't know much about bearings, so I'd be concerned about whether non-dimensional parameters such as loads, duty cycle, or tolerances might be relevant. I'd therefore much rather get the right spec (if it's available) than estimate based solely on measurements. I think I'm going to start a pinned thread pulling together bearing information for different MVHR models that people have encountered. Might be a useful resource given these things inevitably fail and are much cheaper to replace than the motor as a whole.

Thanks @ProDave Is there a reason you took your own measurements rather than contacting the MVHR or motor supplier and asking them for the bearing specs?

I'd do that with something like a plumbing component that I can get locally, but I have no idea what sort of bearing supply places are near me. Seemed just as easy to start by seeing whether anyone else had dealt with the issue given that I know quite a few people have these Brink units installed.

I disagree with those who say all rooms need to be the same temperature in a Passivhaus class dwelling. For example, it's generally fairly easy to maintain lower temperatures (during winter) in upstairs rooms. We have no heating in the bedrooms and it's naturally 2-3 degrees cooler upstairs than downstairs at this time of year. The coldest ground floor room in our house is the TV room. It's the only room with carpet - the rest of the ground floor is polished concrete, which is much better at transferring heat. As well as using different pipe spacing, you can throttle down the flow rate to rooms where you want less heat. You won't get massive temperature differences, but even a couple of degrees can be noticeable. All that said, I agree with those who say you're overthinking it, especially as far as the challenges you think will arise out of using off-peak energy. Our slab temperature has varied by a total of 1.2 degrees over the last two months, with a typical daily fluctuation of about 0.2 degrees. That's with an extremely simple control setup in Loxone that doesn't even take into account outside temperature (the ASHP does weather compensation).

Thanks for that. I did find that (and a few other similar videos) yesterday, but it has a different motor. I suspect most of them use the same bearings but I'd rather not risk it!

I've figured out the motor (EBM Pabst R3G190-RG19-22 (previously R3G190-RC05-09)), but can't find out anything about the bearings. It seems Brink would prefer you buy a new motor for several hundred quid rather than replace the bearings. Thanks Nick. I've shot off emails to EBM Pabst and the UK supplier, but am not particularly expecting a positive reply (if any) before the new year anyway. If you know someone who could give you the necessary info, that'd be great. There's no particular rush, thanks!

See if you can find recycled railway ballast. We used it under our raft foundations. Make sure you get the cleaned version.

The fans on my 9 year old Brink Excellent 400 have been slowly getting noisier, so I'm going to replace them. Our unit is installed in such a way that it's going to be a complete bear to get to the motors so I can replace the bearings. I'd therefore like to order the bearings before I take the unit apart, so I can do the whole job on the same day. Does anyone happen to know what size and number of bearings Brink uses on these units? I could contact Brink, but I expect they're closed until the new year, and I can't find anything about it online. @Nickfromwales, is this something you've encountered? Thanks.

Yes, I think some of them can. In my case, even 2 x 7 kW car chargers and the ASHP pump running flat chat on top of ordinary background loads wouldn't take me anywhere near the limit.

Diversity.

If they did calculations, then they ought to be able to present them and explain their maths. You've paid for it, so demand they show their working. 40 kW is 166 A. Like you're planning, I have a "big house all electric" (290 m2, 5 kW ASHP, 7.2 kW car charger, 3 ovens + induction hob) and my very conservative electrician was more than happy with our existing 100 A supply.

What are you running that could possibly consume 40 kW given you're talking about a max 7 kW heating system? Are you planning something like a 22 kW charger for a car?