joth

If it's like RHI the requirement is only that the EPC contains no recommendations for loft or cavity wall insulation. [Or you have a letter from whoever explaining why loft/cavity is not permissible / economic for your grade 2 listed castle etc etc] https://www.theecoexperts.co.uk/blog/boiler-upgrade-scheme confirms This is not just self-builds though is it. You could own a 19th century home with no heating system at all, and still claim the grant. "Boiler Upgrade Scheme" is just a (inaccurate) moniker based on the fact the majority of intended recipients will have an existing boiler they are replacing.

What make ASHP / controller is it? As @Nickfromwales suggests, our ecodan FTC6 circulates all pumps when transitioning from DHW back to cooling, which means I get a slug of hot water right the way through to the bedroom FCU. So I've put a thermistor in the heat exchanger of the FCU so it can shutoff the fan when the water temperature is above that of the room it is trying to cool! Avoids a blast of warm air hitting us at 4:30am All that said we also has a 3 port diverter valve (mid position valve, stupidly) and I do worry it lets some by. If I knew how to do plumbing I'd change that up.

The 60° comment was for the CH circuit, to avoid needing fan assisted rads. I agree with the other comments that it's by no means a given CH and rads are needed at all.

This sounds fraught with daily prediction challenges. To get a bit of heat into the UFH you'd first need to get 1000L of buffer up to temperature, which may take several hours of sunlight to achieve on a gray day. Then if the house battery runs flat your going to have to fire up the diesel genny anyway, at which point it's trying to cool itself from an already preheated buffer. So ideally you want ASHP to bypass the large buffer in normal use and just pull it inline when the genny is running. But while the genny is running you need to make a call whether to run the ASHP too (higher load on the genny probably pulls it into a more efficient operating range plus you achieve the ASHP COP) or not To run it efficiently the control system will be unconventional and complex. Given the OP only says it is "probably" going to end up being off-grid, I'd first put a lot of effort into seeing if you can actually go ongrid before committing to elaborate multimodal heating design 🙂

Good question. The spec sheet claims COP of 3.16 is for 54.4 °C "reference temperature", which if true is extremely good. Doesn't mention what outdoor temperature though The image appears to show 2 immersion heaters, and the spec had a strange statement: "Energy output includes built in Erods" Erods? I'm skeptical what the real world performance would be, but open to the idea.

I buy it from my local shop, as good a price as anywhere online and it saves me having to hold a tonne of it in stock myself https://www.totalsoftwater.com/products/block-salt/ (Also feels good to patronage a local store rather than emperor Bezos's emporium where I can)

FWIW My comment above about non-finished property was about the ongoing property tax (i.e. council tax), nothing todo with VAT rebate.

> "assuming I don't get permission for an external fan unit" Get the application in for the external ASHP unit, knowing where you stand with that will help other decisions a lot. > "Mixergy tank set to the Octopus tarriff but this is about £5K" Remember that the octopus tariff may not last forever so you want to future proof against prices changes. That said without a bath and in a 1b flat overall DHW should be pretty low. Personally I'd ditch the complexity of the Mixergy and just go for a well insulated conventional UVC - ideally ASHP ready. >GS200 from Ground Sun Not familiar with this but it does seem a legit alternative. Obv. puts a bit more noise inside the building, but so long as you can live with that on paper it seems the tool for the job. Stated COP of 3.5 is fine. It only delivers heating water up to 40ºC so you'll definitely need oversized of fan assisted rads. Again if you can time running it so noise isn't an issue, fan-assisted probably works best.

I know some countries you can avoid paying local property tax on unfinished build so houses often have a not quite tiled roof somewhere that never quite seems to get finished

Agreed. Prior to that thread I had only good things to say about our ecodan, but £100+ per year vampire load might make the premium of the Vaillant seem more reasonable I considered the Mixergy but eventually decided against it mostly because I didn't want yet another cloud dependency in my life. A standard well insulated tank (Oso geocoil) cost a lot less to buy, has very low heat losses, and Just Works.

AFAIK there is no mention here about the WBS providing DHW. It would be a hugely complex installation for an annex, and require a lot of components / plumbing / header tanks etc. Ahh I was going on this comment in the OP: Eventual use will require hot water - preferably instantaneous, as it will be used occasionally and often for shortish periods . Heat from the log burner in the craft workshop will be sufficient. I thought that was saying Heat energy from the WBS would be sufficient to supply the DHW. Now I see that second sentence is probably about space heating and nothing to do with DHW? If so, great. That matches what I was driving towards too. yes, 12kW PV + battery plus an instance water heater sized appropriately for whatever it is delivering to. (Shower? utility sink? hand basin?). A cylinder is not a good choice for something only used occasionally

This must all be triggered by having a third story? (Loft conversion) We retrofitted a 1960s, open plan ground floor including hallway and stairwell, and had no specific fire regulations requirements except interlinked fire alarms (which I'm more than happy to have installed).

I'm afraid I don't understand your question

No the inverter is not dumping 3kW as heat through its heat sink, it just won't draw as much current as it could of from the panels. Like if you hook up a 100W load to a PSU or battery capable of delivering 200W, it doesn't automatically mean 100W is being "lost" anywhere. In the example 3kW is being "lost" via reflected and absorbed solar energy in the panels themselves. Just the same as sun hitting a tile roof, or indeed if sunlight is hitting panels with no load connected.

Good point however the piece I'm assuming but wasn't actually stated is there's also some DC coupled batteries, so it's perfectly possible the panels are pumping more power than the inverter is delivering into AC, if the difference goes into charging battery.

It depends on the app, but I believe the solaredge app shows the inverter output not the DC input, so it is clipped if the panes exceed the inverter W capacity. If you have SE optimisers you can also see the DC generation (Wh per day) as the sum of all the optimisers.

Don't rule out something silly like the inverter got switched off for a few weeks or something. Happened to me! Electrician shut it down and I hadn't realised. Also it could be after 10years there's a fault in one panel making a whole string under perform. I think you can even replace panels and retain original fit, so long as you replace with like for like? I'm no expert tho

Well if serious about using the wbs for DHW it would have to be a cylinder, but it all depends on the expected usage patterns. If it's less than daily use I wouldn't have thought a cylinder would have much value. Certainly in summer you won't want to fire up the wbs just to get some hot water so some sort of electrical source DHW is needed

Couple thoughts: You mentioned it will be well insulated, but the quoted figures (100mm / 50mm) don't match that. Around here you'd need 200mm on floor walls and roof to be well insulated. Depending what degree of activity the gym needs, in my experience you need lots of ventilation and cooling. This means making sure the WBS is not on when the gym is being used, and an MVHR alone is not sufficient for a gym. Generally if either the wbs or gym are in use I expect you'll need a window or 2 open. And wbs probably means low degree of airtightness anyway. Overall I'm doubtful you'll get much benefit from an MVHR over the long run. With that much solar I'd also consider batteries and an instant water boiler

My Zehnder has built in humidity detection and automatic boost, which works ~ok for cooking and showering, but doesn't help one jot for toilet stink bombs Regarding occupancy detection, I have really basic PIR in each bathroom: https://www.aliexpress.com/item/1005003500901521.html £6 (I opened them up and removed the clicky clicking relay, as the transistor can drive Loxone digital input directly). These are totally fine for turning on lights, especially low level night lights and they're sensitive enough to keep the lights on while having and long soak in the bath I could use them for MVHR boost and towel rad but I find in practice triggering those from the temp sensor on the shower is more useful. i don't have a specific solution for the stink bomb, and honestly it hasn't been an issue.

I'd never even considered presence detectors in terms of payback time. I got them to do automation, including automated lights coming on (including low level markers at night), manage audio, set the blinds to reduce glare on the computer screen when I'm in the office, and such like. The fact it can turn off lights and appliances and save money is a bonus. Then, half the motion sensors were there anyway (security system) and the higher sensitivity ones were only £7 each (plus a Loxone DI extension which was £10 per channel) so a completely fine outlay in my book. But heck each to their own, I'm definitely not here to push my lifestyle choices on others. But on that point I'm generally very active and not getting obese, and turning off a light switch would not constitute a meaningful workout for me if I was.

LOL I had thought what I'd achieved was pretty discrete actually. Maybe I'm biased by what I sit underneath in the office: Now that's prominent!

Small update on my FCU install: yesterday I finished installing one of the bedroom ducted plenums and grills. It was a pig of a job to do. Wish I'd done it during the build rather than thinking "oh that will be easy to retrofit". But I'm pleased with the result. Just 3 more to go!! This one: https://www.ventilationland.co.uk/product/35035/slot-diffuser-with-3-adjustable-slots-of-1000-mm.html - along with the plenum, costs more than the FCU 🙄

Cool, post photos when done. TBF I was bricking myself about drilling holes in the 3.2m long porcelain tile, and that backfilling them with resin will look sh1te and collect dirt, so I didn't put up a strong argument for this one.

Thank you, I am. 6 years at university studying it. LOL we know you are! I was (perhaps ambiguously) addressing the OP. I should have said "unless one is a... [nerd] .."