Dan F

@puntloos I'd stick to 1100 max for sure. Where is the fridge? If it's the white box I'd definitely change this so that the fridge is on the end of the run of units and is easily accessible without going round the island from dining table. Also think about how family members will get to the fridge (e.g. to get a drink) when someone is using the sink and/or hob, it doesn't look very practical to have fridge door opposite the hob, even if you do have 1200mm.

Some of the calculations I saw when we were looking at providers used a magic foil to improve u-values. Our passive house consultant told us this was questionable and insisted on ignoring the the TF suppliers calculations (which were done by the foil manufactuer!)

Look at the door specs, this will tell you how big the frame is given a door size (assuming you use this approach rather than do something custom). e.g. https://www.eclisse.co.uk/content/tech_specs/Tech Specs 2018/ECL_Syntesis Flush Single_UK_18.pdf

@SteamyTea I've heard BenQ AUO == Sunpower. Any other suggestions of cheaper panels that might be good candidates to look at?

I havn't read the whole thread, but do you specifically want to comply with M4(2) or have a planning condition that requires it? If not, then this section is optional. 1200mm is nice and wide, but some people do argue it's slightly too wide if you are using both surfaces opposite each other at the same time. Having said that, after checking our plans (our ktichen/garden/living set up is similair) we have 1200mm drawn for the long length of the island and 1100mm for the short length. (might reduce the 1200mm to 1100mm though) We then have 1800mm on the "bar" side of the island. Other than M4(2) I don't think there is any requirement for kitchen spacing anywhere for england. We are renting a house with a huge island and only 98cm from island to the worktop with sink. It works, but hard for two people to pass each other and when the dishwasher is open it's a pain, 105/110 would be better. Given your plans, I would reduce to 110mm, which will give you more circulation space the other side of he kitchen and through to the garden room where you'll feel it more, and this will IMO make the kitchen feel slightly bigger.

Don't know much about all the different panel manufactuers. We've decided to go for panels with i) 20-25yr warranty ii) low degredation that will give around 90% after 25yrs, because we plan to live in the house for a long time and don't want to have to be replacing in the near future. (the good warranties cover all scaffolding/labor to resolve any issues). This led us to REC and LG. But I've heard good things about JA/Q-Cells also which have lower price point with (I think) less warranty and more degredation. I'm going to look into this again though, make sure there isn't a good budget panel that is almost as good as REC.

@joth Is it too late for you to go 3-phase if you are concerned about the voltage issue? Looks like this may be another validation that 3-phase is the best approach for us (vs. 10kW single-phase inverter), but I do wonder if there are any examples of practical issues caused by this or if it is more theoretical..

@AnonymousBosch So a "domestic client" doesn't need to notify HSE directly. But if there isn't a main contractor then the self-builder, acting as the principal contractor, still needs to notify HSE is how I understand it. So in my case, I would need to notifiy and put my details for both i) client and ii) principal contractor I'm assuming

I understand the CDM situation, thanks to @AnonymousBosch's great post. But I'm unclear why a couple of people seem confident that the F10 does not apply if you are a self-builder.. While a lot of self-build project won't meet criteria 1), most will meet criteria 2). As even if you only have 4 people on site typically, that's only 4 months. Is there anything anywhere that says self-builders don't need to submit an F10. For anyone that's submitted one, have you put yourself as the main contractor?

No, because you can easily run 15kW array with a 10kW 3-phase inverter and still stay within the standard 3.68kW. DNO care about export and potentially also the inverter size, but AFAIK they don't care how many panels you actually put on the roof.

Will you be using GSE integration? If you are, their install guide talks about optimizer locations in relation to GSE unit and the panel. 5kW/16 = 310W? Is it worth looking at a higher wattage panel to push this up? Given the split between south/east/west roofs, a slightly larger install capacity isn't necesarily going to cause an issue with export, but would mean you have more generation in spring/autumn.

I've been told by PV suppliers that some DNO's don't really accept G100 limiting and instead insist on a maximum inverter size. How much truth there is to this though I don't know, and it may depend on your specific DNO. Regardless of your inverter size though (which may be limited for various reasons) you can still oversize you PV array. Solaredge single-phase inverters support up to 155% over-sizing, and if you consider "effective oversizing" rather than "STC oversizing" (for example if you have panels on east and west roofs) you can actually oversize even more, you just need to run the calculations based on location and pitch/orientation. In our case, according to the Solaredge designer, we could put as much as 17kW installed capacity on the roof with a 10kW single-phase inverter and only loose maximum 4% to clipping in June. We've decicded to go down the 3-phase route though, even though the DNO will allow 10kW export/inverter on a single-phase as we already have a 3-phase supply.

You'll need to give ASHP size some thought as you'll probably need quite a small one for heating, but DHW might require a larger one. What are you doing for DHW storage? Also, another reason to use ASHP is potential for cooling in the summer which works well with passive slab type foundations.

I've seen various people are on the forum using buffer vessels of around 70L, but is there any formula/method that can be used to calculate/estimate the required size? The reason I'm looking at this is because we need to decide on ASHP size. We only really need max 6kW for heating demand, but a larger ASHP would be preffered for DHW. The issue with a larger ASHP (say 10kW) is that it's not going to be able to module down so much and there is a risk of cycling if the buffer vessel is too small. So I'm wondering how I would work out what buffer vessel size would be best for a 10kW ASHP (assuming it can only modulate down to 5kW output) if UFH flow temperature is 28C and total heating load is for the house 2.9kW. I assume ASHP flow temperature also has something to do with it, as a bussel vessel with need reheating less if it's at 45C than if it's at 35C, meaning less cyclig?

Have you looked at https://www.unipi.technology/ ? Edit: mm, these are somewhat less lightweight then I thought...

So Octopus have now confirmed that: 1) They are installing 3-phase smart meters, but this is paused due to COVID-19. 2) Metering is "vector sum" across all three phases. (This confirms what @joth concluded from his investigation, and means imports/exports on different phases at the same time are netted out. Based on this, siwtched back to 3-phase now rather than upgrade later, as it seems there is nothing to loose and we already have a 3-phase supply on-site. Need to do load-calcs for the house, but this will probably still use the a single primary phase for house consumption.

Take a look at: https://www.sgd.org.uk/find_a_designer/default.aspx https://www.bali.org.uk/members/directory/ We met two types of garden designer: - Local garden designers who weren't members of SGD/BALI charging around £1,200 for design. - SGD/BALI designers, including some qualified landscape architects, who wanted to charge £5-10k+ But we couldn't really find anyone between the two extremes ? In the end, because we we have level thesholds and we wanted to ensure all the drainage was properly done we hired a landscape architect and not the local garden designer. It's costing more than we expected to pay on garden design, but I guess it's one of the things that seems secondary, but in actual fact is it's own project/profession and needs time/money if you want to achieve a good result. When you say "proposed costs", did you have someone else build it more cheaply in the end then?

Expression of hope, more than anything else. But I think there is some kind of legislation about smart meters being used everywhere by end of 2020. I think we have a plan though for our build: - Move our existing 3-phase connection to garage and get our curent single-phase meter upgraded to a smart meter. - Wire the house on a single phase (unless loading calculations show this is an issue, but it shouldn't be). - Use a single phase 10kW inverter, which will allow for oversizing the array to up 15.5kW of installed capacity across east/south/west roofs (there isn't room for much more anyway unless we go for more expensive 360W+ panels, and 15kw is a lot). - If required we can upgrade to 3-phase further down the line if/when fast car charging is important. At this point we wouldn't actually need to do anything to PV as this would export generation on phase 1 and could be consumed by a car-chager on phases 1/2/3. - The only potential issue with staying with single-phase is if we decide a second battery makes sense, as it's unlikely the DNO would allow 10kw + 2 batteries on a single phase. Also there is one downside to a three-phase inverter; unless you have an ac-coupled battery on each phase the inverter will switch off when there is a power-cut or you go "off-grid". With a single-phase inverter on a three phase supply you don't have this issue.

Agree, but this time next year hopefully these meters are avaialble. So it's still worth understanding from a planning perspective. Did you go for 3-phase inverter because you weren't allowed to install/export much on a single phase, or for some other reason?

So, a PV supplier/installer in our area just confirmed that they have personal expeirence of: - Net metetering across three-phases. - Powerwall exporting to compensate for consumption on other phaaes and this working in the U.K. This doesn't mean 3 phase wiring or 3 phase inverter necesarily makes sense for us (given we've been told we can export 10kW), but is good to know. In fact we could upgrade to three phase supply in the future, but still use single phase inverter (if our array isn't larger than 15kW) without an issue and a 3-phase car charger on a bight summers day would still utilize PV fully via the 3-phase net metering.

So the issue you have is that you are exporting, but given you don't have a smart meter this is being ignored. Have you been told that exporting will be counted when you have a smart meter, or specifically that import/export across phases will be netted out once you have a smart meter? Out of interest, how much PV do you have across the phase?

This isn't offical, and the guys not even an electrician, but it does explain how this would work in theory and matches the Sonnon documentation. https://www.youtube.com/watch?v=YDFfqqlAJEw Also, this is someone in South Africa that see this behaviour: https://teslamotorsclub.com/tmc/threads/battery-self-consumption-across-all-three-phases-with-1p-pv.185180/

Another interesting element to the net metering across phases is that, in theory (based on Sonnen/Tesla documentation) you can connect a battery to a single phase and it can compensate for usage on other phases by exporting. What this means is you can effectively, in an indirect way, use a single phase battery for consumption across three phases without import costs! There are a number of caveats to this though: - This won't work when there is a power cut (so everything you want backup for should be on phase that the battery is on) - Noone has any concrete proof that: i) UK 3-phase SMART meters will work in this way (although everything seems to point to the fact they will given the documentation that @joth referenced). ii) It's unclear if this battery "phase compensation" approach, supported by Sonnen/Tesla is enabled/supported/allowed in the U.K. If this does work and is supported it would be the preffered approach for us I think, as there would then be no downside and we'd have 3-phase for a car-charger, could potentially use a 3-phase ASHP and I think I read somewhere that having a 3-phase 13A system, is probably preferred to a 40amp single-phase system (impact on voltage?). This is some (U.K) Sonnon documentation which mentions the battery compensation: https://midsummerwholesale.co.uk/pdfs/sonnen-net-metering-technical-note.pdf

That's exactly what we already have (just need to get the SMART meter installed)! The old bungalow we demolished already had it.. We have no immediate need for 3 phase (apart from faster charging of a future EV), so really just trying to work this out from a PV planning perspective. A three phase inverter probably makes the most sense given the size of the array (even though the DNO will apparently let us export 10kW), but we wouldn't want to use a three phase supply/inverter and for this to significantly impact self-consumpton. None of the PV suppliers I've talked to really know much about any of this at all ?