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Ok thanks, plenty food for thought

So just so I'm clear on options... Option 1: - 18kw 3ph ASHP and UVC in annex supplying heating and hot water for all 3 buildings (annex, house and workshop) Option 2: - 18kw ASHP in annex powering heating for all 3 buildings UVC in garage connected to heatpump supplying annex only UVC in house powered by electric only for hot water in house and workshop Option 3: - 12-16kw ASHP powering house and workshop located at annex 4-6kw ASHP powering annex located at annex UVC in garage connected to heatpump supplying annex only UVC in house powered by electric only for hot water in house and workshop I think that captures it? Question is...does option 2 and 3 still allow for grant? Thanks

Does it count if UVC for annex is still powered by heat pump?

Oh I see…there goes that idea then…

Yeah the MCS installer did the heat loss calcs. I’ve asked him for the detail. Bit rough maths was 12kw for house, annex 4kw and workshop 2kw. I think I’m coming round to idea of UVC in house outhouse. If it’s to be purely electric fed would I not need a heat pump type? I think he had spec’d the uk cylinder elite heat pump one. What abput one ASHP for house and workshop and 1 for annex? But both located at garage…

Well the idea is to have zero equipment in the house so when it's likely knocked down everything can still operate. We did originally consider the ASHP on that side elevation but it's going to be a patio area as well as it gets evening sun. In the outbuilding, yep it will have UFH in the concrete slab and also hot water. A lot of different options to consider...

I'm really appreciating the feedback, thanks. Knocking down maybe in 15 years earliest. Also a possibility we won't. I think regardless of 1 or 2 ASHP, we like the idea of locating heat pump away from house. But yes, it is a lot of money, but idea is we are spending as little as possible in actual house, as for whatever reason the previous owner really over specc'd on radiators. The cold water will likely be mdpe or insulated mlcp as it will be deep enough in trench. The hot water return is therefore in that quad. I've attached a photo to show. So green line is heat pump(s) location, and other side of that wall is where plant room will be. That garage will be converted in to a 2 storey living block, with UFH on ground floor and rads on 2nd floor. It's approx 12x6m. Pink line is trench to the old boiler outhouse where it can easily connect to existing pipework for CH, H and C. It then connects in that outhouse in yellow line out to workshop which will be around 8x5m.

Thanks for the insight. We are fighting a few competing things in coming up with solution. One of the main things is we may knock down and rebuild house in the near distant future. So by housing all ASHP, HW, CW as well as new electric meter, etc in garage annex it somewhat helps with that. If it helps, we are looking at using insulated pipe like this? https://www.flowsupplies.co.uk/shop/if-bq32-32-25-20-isoflow-32-32-25-20-quadruple-heating-sanitary-dhw-160mm-duct-2067?category=21#attribute_values=350,388,454,456 If I wasn't clear, the new workshop/studio is a further 15m to other side of house which will also make use of ASHP with UFH in the slab.

Yes I think so. Why do you ask?

Yeah I will be paying bills for rental for air bnb. the garage annex will be heated from the ASHP as well. the annex is about 20-30 metres from house. The idea is plant room will be in annex. So HW cylinder and power tank will be in there with ASHP nearby outside

Ah I see. That was me being dumb on that front. Yeah it’s MCS install. I’m hoping to get the full 11-12 export given we are moving to three phase. I haven’t done full maths yet to compare export vs HW divert yet. On the HW front. Is there any guidance to help on tank size? In the house we will likely have max of 2 bathrooms. In the annex for rental it was also likely have 2 bathrooms. Is 300ltr too small for this? Thanks

Maybe it's my simple misunderstanding! The ones with twin coil seem marketed at using excess solar to heat up water?

I'm just finalising my new ASHP system to replace existing LPG boiler. I'm also about to get solar installed, with 12kw generation and 16kw battery. It's a larger 18kw 3 phase ASHP as it will be powering heat and hot water to main house, garage annexe and a separate workshop. He's specified 300ltr HW cylinder and 500 litre powertank and pump as our mains pressure is terrible My ASHP installer doesn't seem hugely on board of specifying a twin coil HW cylinder and seems to think a heat pump cylinder would be fine with normal immersion. What is consensus here? Thanks

So had a quote back which was pretty reasonable at £1500 inc vat, but with me doing excavation and ducting. I've attached the plan they sent me. Currently my supply is overhead from the pole and they are mandating it needs to be underground following yellow line. However it's quite a tricky run with lots of concrete. However, I'm now thinking maybe of using the wooden pole near the garage and house the meter, etc in garage or behind garage. I've already got a trench open (in pink line) to then feed back to house. There is also the existing 25m2 armoured cable between house and garage. What are thoughts on reconfiguring and housing in garage? Thanks

Ok thanks for feedback

Hi there, I'm after confirmation that I don't need planning permission for a 40sqm workshop. It seems people confuse that anything over 30sqm requires both planning permission and building regulations? The house I'm in is within green belt, but previous to buying it I got confirmation from the council that I still have permitted development rights. All other aspects I'm complying with, i.e more than 2m from boundary so can have pitched roof and also overall curtailage is fine. Thanks

Thanks for replies. The outbuilding will be around 8m x 5m. And was planning on doing underfloor heating in slab. I was also future proofing a little incase someone in future uses building for any other purpose than a workshop

Thanks for reply. When you say 25mm close cell insulation, what do you mean?

I should add the trench will be circa 700mm deep as also running cold mains water.

Hi there, I'm looking at getting a heat pump installed this year and as part of it I'm provisioning to run feeds to a new outdoor workshop which will have underfloor heating in slabs. Based on my house and this, seems like consensus is a 16kw ASHP. 1 or 2 that have quoted so far just said to run 28mm insulated pipe from house plant room to new workshop (circa 15m). I've already got a trench dug for other reasons so want to lay it now in readiness. Is something like this ok in either 25 or 32mm? https://www.plumb2u.com/32mm-pre-insulated-mlcp-pipe-25m-coil-red-palpex-32025r-c2x41327360 Thanks

Thanks for all the further replies. The company installing the solar submitted the G99 last week to DNO, so will find out in due course. I did also ask for formal quote on 3 phase, so that should also be due back in next week or 2. Sorry if I'm being slow, but I still didn't quite work out if having 3 phase inverter is worth it

Thanks for feedback. The 16kw was advised as part of a recent quote I had. I was already stretching budget to get 16kw battery. But I'll take another look! But as you said it seems easy to add later. I've definitely maxed out what I can with solar at 32 panels for suitable roofs.

The zappi works on single or multiphase. I always charge overnight anyway, so it's not deal breaker if it stays on 7kw. On the main house I'm replacing an existing LPG boiler with heat pump. I didn't realise it would somehow invalidate that grant if i got a separate gas boiler later for other building? Thanks

Hi there, I'm just about to go ahead with a deposit for a solar system but wondering if I should be future proofing more. Currently on single phase which powers the house and a large separate garage and flat above. That is fed on a dedicated 24m2 cable. Solar wise, we are going sig energy and looking at 16kw batteries and 14kw PV. As part of this, we are also getting the multiphase zappi charger. All of this will be housed in the garage. Upcoming in next year or so: - ⁠⁠16kw ASHP. Power input I think is around 6kw. This is sized large to also provide heat for workshop. New large workshop building. It will have a lot of equipment, some needing 16amp supply but as it’s just me in theory I’d only use a large dust extractor (2-3kw max) and 1/2 machines at a time with max maybe an additional 2-3kw. The existing garage will be converted at some point to an air bnb which may put more concurrent demand on. Likely we may but a small gas boiler in to utilise existing LPG tank we have in order to remove existing electric shower and small water heater for tap. I've attached a few photos of current setup. So i guess my questions are... With my future demands (whereby there could be a mix of house, airbnb garage and workshop running at same time), should I be considering 3 phase? Even if the above demands 3 phase, is it worth getting solar 3 phase equipment? Or would it make more sense to seperate phases to garage, house and workshop? I'll also note that utilising 3 phase for the car charger and workshop for bigger equipment is a real nice to have Thanks

So looking at photos on internet for biodisc, I think the inlet is at the correct height relative to the machinery. It's just set down a lot lower than maybe it ordinarily would be and I guess essentially has another riser (or neck if that's what you meant @ProDave? on top to get to ground height. I think the reason it's set so low is that the primary drainage comes from back of house and all the way around side. So it's probably a good 30 metre run in total before it gets to STP. Apologies I thought I'd sent a photo of inside orignally. See attached now. Arrow shows the inlet.