joth

In that case you might as well get UKPN to put in the 3 phase head whatever, if it doesn't cost much more. All my research (talking to UKPn in particular) was that you can definitely get any supplier to put a single phase meter in on it, but having the 3ph head now will give you future flexibility should you ever need it.

Note you don't have to be on SMETS2 meter to get vector sum / net metering. e.g. Sprint 211 supports it. (But conversely, having a SMETS2 is a good way to ensure it, as it's part of the SMETS2 spec) Most meters support multiple modes, and on a domestic supply it should be possible (pandemic aside) to find a supplier that will put you onto net metering. When I spoke to my supplier about this a couple years ago, they admitted they often get this wrong at first install and need to send a technician back multiple times to get it right. YMMV

Yeah I've turned it from "Adaptive" to "Fixed" temperature profile, and *think* I've forced it into "summer" mode (it's rather ambiguous, as normally it won't start summer mode until mean outdoor temp hits 15ºC minimum, and we're still only at RMTO= 10ºC, but in the app there is a "start summer now" button I pressed, but it doesn't give much feedback it actually did anything when RMTO < 15) I then set the "Cool" temp profile to target 19ºC, and as it's always at about 21ºC indoors, this means it's pretty much always in 100% bypass mode, just adds in a little heat recovery overnight when the outside temp really drops Downside is we can regularly have >22ºC upstairs yet <20 downstairs, which together with the ground floor having a lot of porcelain flooring means there's still times the UFH might want to come on, but yet the MVHR is in bypass mode, which is obviously nuts for energy efficiency but we have to get the place comfortable before really starting to optimize this. But for all that, even with the supply temp now at 13ºC overnight and the bedroom supply vent opened right up, the room still rose from 21 to >23ºC last night, pretty much proving that it doesn't matter what we do with the MVHR temperature, it's the low flow rate that makes it insufficient for dealing with body heat. Yeah this is another avenue to look at, although it does feel a bit like failure to start down that path, I'll try that when other options are exhausted. Indeed. It was just aimless musing really, but the thought was an indoor to indoor heat pump that constantly collects the gathered heat from upstairs and relocates it back down into the ground floor slab.

yeah I knew well enough it wouldn't be sufficient for dealing with summer overheating and crazy solar gains, but honestly hadn't considered it's an order of magnitude too wimpy to deal with a single sleeping human. Wish I'd done the maths in advance. This is really helpful to confirm that you see the same issue and have had to make a solution for it. Unfortunately this solution doesn't work well for us - we are in town with a train line one side and sometimes busy road the other, and part of the inspiration for MVHR and passive-house design was the great sound proofing that insulation and the 3G windows bring. (And it does work great for that, modulo the overheating) Time for me to start designing secondary ventilation I think! We do have a fan coil in the loft, but issue is we need bedroom cooling even when the rest of the house is borderline needing heating on. It seems mad to enable active ASHP cooling during the heating season. (And, it's not that easy to do this dynamically with our heat pump). So need to figure another plan. Ideally I'd have a water to water heat pump that could cool upstairs while pumping the heat down into the the ground floor UFH First, I think I'll see if I can get some stack ventilation working through the room and out to the hallway vaulted ceiling.

Yes, thanks I meant to reply on this one: definitely planning to perform this experiment but waiting on installing curtains for the other rooms ?

Thanks! The beauty of using the Google search box calculator is it automatically performs simple unit conversions like this (and verifies the resultant units are what you expect) Paste either these in a search box and you should see it work: 1.012 (J /g)/K * 1.2041 (kg/m3) * 151/5 m³/(3600s) * 1K 1012 (J /kg)/K * 1.2041 (kg/m3) * 151/5 m³/(3600s) * 1K

Exactly! I don't see how our situation is that different, I know others happily keep bedrooms a degree or two cooler than the rest of the house so trying to figure out if there's anything specific we're missing that is resulting in ours being warmer rather than cooler than the rest of the house. FWIW the bedroom door does have a smaller than average undercut, just as you are planning, I thought this would be fine as the bedroom + ensuite would makes its own balanced pair but it is not enough to keep the room at a comfortable temperature, but it doesn't seem so. I don't think widening the door gap would help though, as leaving the door open a crack does not seem to help much - there's just not much airflow through that door because the bedroom+ensuite are already acting as a pair. I know this is not seeking a reply, but for avoidance of doubt the issue with Thermal mass is it requires a temperature gradient to put any energy into (or out of) it. So if the whole house is already at or slightly above target temperature, the room has to overheat by a couple more degrees before it'll get much effect in moving energy into the mass (or through the fabric of the building). This is probably why, we see the room temp shoot up but then "level off" at about 23ºC each night. Also, there's always going to be a limit to how much can be stored, and depends on being able to dump all that stored energy during the (hot?) day while the room is unoccupied. If I'm unwell with a fever and have to stay in bed for several days I don't want to be overheating because the nearby thermal mass has "filled up"! I'd rather the system can deal with moving out the heat perpetually, to stay in equilibrium. My maths so far [which I still hope is wrong!] show that MVHR is only able to move energy at a fraction of the rate a human generates it, so is doomed to overheat without a designed in secondary pathway to carry energy away.

Thanks! yes I removed the "multiply by time" from my own calcs (hence why the Google box resolved to W not J) but forgot to remove that term from the formula - fixed.

Recently moved into our renovated house, temperature is great everywhere, around 20ºC, except the master bedroom that sits at about 21-22ºC all day and shoots up to 23+ every night. I want to get ahead of this before the summer overheating risk really starts! Full build context below. Our goal would actually to be to keep it cooler than the rest of the house, e.g. 19ºC The bedroom + ensuite have a supply + extract duct so I was hoping these would make a balanced pair and not need much additional ventilation. Even if it's purge ventilated all day, as soon as we try and sleep. it rapidly overheats. Thanks to @SteamyTea I have the formula for the rate an MVHR can move energy: P = SHC x Mass Flow Rate x ∆T. SHC of air at 20ºC = 1.012 J/(g.K) Mass of air = 1.2041 (kg/m3) Flow rate of the entire house air supply = 151 m³/hour - Lets assume 1/5th of this can be sent to Master bedroom. (A bit optimistic as we have 7 supply vents, but, whatever). Plugging all this into a good old Google search box: So for every 1ºC of air temperature difference, the MVHR can remove 10 watts of heat generation per room. That seems far too low! Where have my calcs gone wrong? 2 adults sleeping will put out about 80W each (and a bit more after a couple glasses of wine). So the MVHR supply, at 30m³/h, needs to be 16ºC colder than target temperature to keep the temperature constant. That seems completely insane! Where have my calcs gone wrong?? Our poor Q350 still thinks we're in "winter heating season" so is recovering all the heat it can, pumping 20.5ºC air into the room. No wonder it overheats. Unless I can set a different supply temperature of flow rate for the bedroom vs every other room, it seems sure to overheat. OR I need to put the whole MVHR into bypass mode, and have every other room freeze overnight. OR I need to install a secondary ventilation system to circulate the air from this room to the rest of the house more actively. (Leaving the bedroom door open is not a preferred option, as we want to keep pets out, and also it opens to a hallway atrium with a too much glass that will let light into the room at 4am.) Does this reflect what other MVHR owners find? How do you manage this? Thanks for reading this far ? @Dan F may also be interested in this, as I know you are also planning an isolated supply/extract for bedroom+ensuite. Full build Context: 151m2 house, 2 occupants. Passive house enerphit standard (25kWh/m2/yr). Zehnder Q350 MVHR House is being maintained 20-21ºC via solar gains and (as needed) ASHP to ground floor UFH. Upstairs has no heating system. Master bedroom is on first floor, with rockwall beneath the floor boards. It has North-East aspect, so some morning light but little in the way of solar gains or other heat sources. not huge, about 30m³ volume but some of that taken with cupboards. The attached Ensuite has UFH mat, which just operates 1 hour each morning. Warm loft above it.

I'm amazed a tax advisor company can write that much article and not mention the CGT aspect! The normal advice is to put an exercise bike in the office and say it's a dual purpose office/gym. https://www.taxinsider.co.uk/working-from-home-don-t-lose-private-residence-relief-ta

Bear in mind this will likely make the office portion liable for capital gains tax when the house is eventually sold. In fact even if you don't take the tax break, having an area dedicated to working can open up CGT liability, but taking a tax break to build it basically predeclares this to HMRC https://www.ftadviser.com/investments/2020/08/12/advisers-warned-of-tax-implications-of-working-from-home/

kWh indeed, have a ?

Total consumption was 603kW, of which 288 was self consumption of PV. PV total generation was 900kWh, of which 612 was exported. (So exported about double what we imported) April was only our second full month living in the house so not yet put a lot of effort put into implementing energy time-shifting (I only just built the immersion controller yesterday! Previously I was using a dumb timer switch) but I'm not sure we'll make a major dent on this as a good chunk of the remaining consumption is cooking and background load.

Whereas I exported 611kWh in April alone. YMMV, it's really up to the buyer to do their own maths and make their own decision

I think you're right that Eddi supports net metering across sum of the 3 phases, but Immersun can only monitor a single phase import/export as it only supports one CT clamp Page 30 https://myenergi.com/wp-content/uploads/2019/04/eddi_manual_v2.3_english.pdf Page 21 https://www.immersun.co.uk/wp-content/uploads/2019/11/immersun-installation-and-user-manual.pdf

No - I see now I worded it ambiguously, but I was replying to this: I meant if the goal is the most efficient system possible, getting both the micro-optimizers (this topic) AND an Eddi/iBoost will be best. It really depends on your definition of efficiency though: electrical energy captured per year per £ of capital investment, full lifetime financial ROI, or CO2 saved, will lead to different optimization choices.

Not likely, I think it will overrun the max voltage on the optimizer. Obviously "both" would be most efficient, but in a run off between these the HW tank redirect is almost certainly going to give the best £ ROI. The larger and better insulated tank, and the more HW you you expect to use from it, the better the payback. Sounds much better than other micro-optimizers. Our contractor had horror stories of installing a system where each micro-optimizer had a separate AC cable that had to be brought inside the building before connecting together. Resulted in dozens of penetrations of the airtightness envelope and a lot of taping and remedial work to pass the air test.

Added a third pro of future proofing, as it's worth calling out a house will hopefully last several generations, it's hard to know what will be needed in future, but if it's only £20 to prepare for it, why the heck not it's worth calling out: you can get a 3 phase supply and only connect up one phase of it to a single-phase meter, and just leave the other 2 there spare in case of future needs.

Couple thoughts - if you get the SolarEdge add on, make sure you get quotes with the newest HD-Wave SolarEdge inverter as these are designed to work with the optimizers (only) and have cost savings based on that. (No MPPT tracking in the inverter, relies on the optimizers for that) - the other 2 benefits of SolarEdge optimizers are (i) provide lifetime per-panel performance monitoring and graphing, (ii) auto safety cut out if the string is disconnected from the inverter. I like these extra benefits, but really they are mostly interested for tinkerers and enthusiasts. If you just want to fit and forget PV then they really don't add a lot. (But IMHO grid scale Solar PV is getting so good I think domestic installs are increasingly the domain of enthusiasts only; the ROI is borderline and might actually make less sense over time)

Seems unlikely to be a problem It's like a vortex with the water coming out at speed is directed in a stream running around and down, and the top lip folds inward / over slightly so if anything did splash up it would get knocked over and directed over anyway A picture may help

Yeah I doubt it's a binary decision. Simply put, the lower the cistern, the more frequent some brushing will be required to remove clingers

Maybe a hinge-pin doorstop would work? Depends on the door and its hinges, of course

I really have no idea! we were advised by the shop salesmans to use "Geberit Omega 12 H112 WC Wall Duofix Frame" when using a "GSI Pura 50 Wall WC Pan Swirlflush" and can confirm that combo works great, but I cannot say how well that information generalises to other brands and heights. Sorry!

Just following up here as I'm really finding Texecom a pig to deal with. The PSU in my Elite 88 panel failed after 2 months. I had the installer replace it and never went through the hassle of claiming it under warranty. Now the Texecom Connect gateway has also failed. Texecom have (eventually) provided a return number, but require the return to go via the supplier. I bought it online; the Supplier is flat refusing to reply to phone or emails, and the credit card company won't take up the case as it's 11 months old (well within 2 year warranty, but > 6 month they will back). I would just suck it up and buy another, but it's borderline useful product (equal parts annoyance and reassurance to have it), and given the appalling failure rate I've had so far with their hardware I'm really loath to reward them with more sales. Just got through to tech support once again (our 4th conversation on the topic) and they're shipping me a replacement today, so I will remove this whinge awaiting a fairer judgement when this outstanding issue is actually resolved!

LOL. It's all a bit heath robinson, but this actually works. I used a relay to switch a 5K6Ω resistor* in parallel with the UVC tank thermistor, and magically the controller believes the internal temp has jumped up by 10ºC meaning it will need to get that much colder before the heatpump will fire to charge it up when in this "set back" mode. That'll do. (* - experimental data: at 49ºC the factory thermistor reads 2kΩ and popping 500Ω in series drops the readout to 43ºC; putting about 6K in parallel reduces the effective resistance to about 1500Ω which increases the the readout to 59ºC. It's almost certainly non-linear so the effect of the resistor in parallel will be more pronounced at lower temps, somewhat unfortunately. I guess if I really wanted I could pull the thermistor out of the tank and put in different temp cups of water and find out.)