SBMS

Sorry Gus I'll be honest I'm not sure what you mean about designing a system based on what is available above the floor?? For clarity: am doing UFH downstairs, and wall mounted fan coils in bedrooms upstairs? Not sure why I would need 'more loops' for FCU cooling? They are on one circuit, drawing water from the buffer? Might have misunderstood though.

Thanks and understand everyone’s points. Let’s just assume I understand everyone’s points that I may not need to run it that cold and could run above dewpoint temp. Id still like to size my FCUs appropriately and can see no downside to have a system that can do 10 deg supply - even if its only on a couple days a year. From the literature it looks like the heat pump does provide this and it’s design is quite similar to my niaive design that didn’t rely on the Panasonic controller??

Thanks for this but seeing as I have already installed and lagged pipes and CAN run at 10 degrees (which also dehumidifies) I’d like the option of it. Would also like FCUs sized appropriately and not oversized to cope with a reduction in output when running at 16deg. If it turns out I don’t need to I can simply set both zones to 16 degrees, enjoy a better COP and achieve the same. Im just keen to understand if the heat pump natively supports this…

Is the same issue present in the Panasonic ‘2 zone layout both mixed’ schematic? Or does it control The mixing valve using the zone water sensor?

This looks almost exactly like what I designed but it’s built into the heat pump!! Is that a fair summary??

I wasn’t sure if the Panasonic dual zone control is built for heating - not for cooling but that seems To indicate it might. Alternatively I wondered if I had to provide dual zone cooling by hydraulic means. i am not an engineer but was thinking… Heat pump produces 10deg water into buffer FCU takes 10 deg water direct from buffer and returns back to buffer. UFH branch comes off buffer with a 3 way thermostatic mixing valve with a hard min of say 16 degrees. Valve blends the 10deg water from buffer with the return from UFH circuit with output to the UFH. UFH circuit would be separately pumped and return to buffer. i could also go for a more advanced controller at the mixing valve that could read the UFH temp and mix accordingly based on the temp - or even integrate with a dewpoint sensor. Would something like the above work?

We are in the process of installing all the pipework for a Panasonic M series ASHP - 7x fancoils upstairs and UFH downstairs. My goal - and reason for picking the Panasonic - was the ability to run dual cooling zones via the ASHP. My plan if it gets hot was to run the fancoils at 10 degrees and the UFH at 15-16 degrees. The installer - who has been great - has had some conflicting information from Panasonic. Initially we were told that this was fine, and the Panasonic supports dual cooling zones, but we've been waiting for a hydraulic schematic from Panasonic. Today we had a technical engineer from Panasonic tell us that he's not sure this is possible natively with the system, and its back to us. We are seeking advice further from Panasonic tech installation. In the meantime - has anyone managed to design and install this system to produce an FCU cooling loop at 10 degrees and UFH at a higher temp and if so how? Our installer is looking into it as well and may come back with a design, but are rightly nervous of designing their 'own' and not following a Panasonic approved schematic.. I know that many will say that its not necessary, run it at one temp etc. I get that, and if thats the fallback so be it. But we've lagged all the pipework for the FCUs, installed condensates throughout and basically prepped it for low temp cooling to maximise the cooling output of the FCUs. I really want to make that work, without having to push 16 degree water around both circuits and would be grateful if anyone has got this to work, or knows of a way.

Thanks Nick - is it the same for the wall mounted unit? I couldn’t find any information on that one..

Currently looking at the Panasonic aquarea heat pump and the wall mounted fan coil units upstairs. Has anyone any experience of piping these up and can advise on where/how the condensate outflow is connected? Can’t find any installation manuals online but have seen a drip tray for a parts list. Would rather it was plumbed in and hidden Than a drip tray. anyone installed these? Looking at the P-FMM15 for reference - https://www.aircon.panasonic.eu/GB_en/model/p-fmm15/

What have they calculated your design heat loss as? 7.5kW or 4.35?

I might have got this wrong but isnt wattage a measure of energy transfer per second??

Yes! Although you need a bit more Power to account for the demand on the heat pump to heat your water as @JohnMo says. When I look at the heat loss spreadsheet today it makes sense but it’s taken a lot of learning and understanding actually to make sense of it from a lay persons perspective. It’s just as others like @JohnMohave said probably much more eloquently than me but I’ll try and simplify it to my level!! It’s not really immediately clear but the sheet provides you with two things. The first set of figures is all about heat loss sizing. So what the 3090W figure is telling you is, when it is the worst case of -3 outside and you want say 20 inside how much heat is your house losing instantaneously. Actually it’s per second because W is already a measure of energy per second. 1W is 1 joule per second. So your house is losing 3090W - or 3090 joules energy to heat per second So this sizes Your heat pump. To keep your house at the temperature you want your heat pump needs to produce 3090W of heat to offset the loss - every second. There’s also hot water production to bear in mind as mentioned above. Your heat pump might be producing hot water and offsetting heat loss so you need some additional power output. The second part to the sheet attempts to work out the total heat loss across a monthly/annual basis. This is where time comes in. If you have 1 hour at 3090W that’s 3kWh which is the unit of charge for electricity. So really the second part of the sheet attempts to calculate your total consumption, factoring in less consumption in summer to winter. Don’t forget that the total consumption is NOT the total electricity usage. Your 12kW heat pump might only use 4kW of electricity to produce that 12kW. That’s its coefficient of performance and a unique feature to heat pumps over say gas boilers. So take your total consumption and divide it by the average CoP for a rough idea of electricity consumption - and therefore cost. sorry if this was all really obvious - i found the sheet required a bit of basic knowledge which I didn’t have when i first started learning about this. Hope it’s useful for someone!

Don’t think Jeremy’s spreadsheet calculates this it’s a manual entry

Also I found heatpunks calculator to be pretty good.

Don’t worry I had the same challenges. Don’t forget the spreadsheet is an estimate so if you use external vs internal wall/roof areas I wouldn’t imagine it’s hugely different. Youll get a higher heat loss by using larger dimensions remember. . Internal floor area is measuring heat loss on ground floor so only put in the floor area of the ground. There is no loss through intermediary floors. The ‘total heat loss’ cell (3090W) gives your worst case heat loss when it’s -3 outside. I would question your house volume though that looks really small if you have 259sqm floor space multiplied by 2.4m that’s a minimum volume of 621m3. Are You sure? 0.4 ach is a bit low as well id go higher.

Our posi rafter roof used Cullen universal hangers around £1.70ea for bulk order.

Ah - We had the same birds mouth at ridge but pasquill insist on hangers as well! Think they did both in the end 🙄

We had same roof design as you but roof manufacturer also specified hangers. Where were your rafters fixed into the ridge beam?

100% option 3. We have full perimeter parapet and ended up going warm roof. That and 100mm isn’t really enough insulation.

As the OP after much consideration have decided to go standard mains with trailing dimmers for downlights and 24v strips where possible. I’ll be using the loxone system. I think my ethos is different to yours - but I’m also waaaaaay less electrically proficient than you! I want everything automated (I walk downstairs at night, presence sensors detect me, fade up stair lights etc) coupled with scene based lighting (a touch control has predefined scenes that controls the layered lighting based on what we are doing in the room). But good luck with your approach and maximum respect for trailblazing and trying something different! Would be great Hear how it goes.

Isn’t this codex?

Claude local agent maintains a persistent context history across the project. We use Claude extensively in the department I look after (dev team). we evaluated ChatGPT but its context window at the time was still inferior to other agents like Claude. From memory ChatGPT can handle small to medium repos - think it’s around 100k tokens in its context window. Claude can do about double that and has context awareness of most of our software project. As your project grows you’ll start to see ChatGPT wobble when it loses or refreshes its context and it’ll start hallucinating about generated code. We tried codex back in 2021 but it was a bit limited. Revisited it earlier this year and it’s really impressive - closer to Claude in its context window and can go from zero to app independently. I think there are lots of cited examples of creating software from scratch using ChatGPT, Claude etc. We have been experimenting with generating a document structure with chat spec files in each directory and getting an app generated from iteratively reading the directory structure to generate the app - this has worked surprisingly well.

Copilot I was referring to copilot chat which does have full repo awareness… However if you think ChatGPT is magic have a try at Claude. It has full project awareness.. can execute build commands..dependency installation…build lifecycle etc.

GitHub copilot does all this integrated using chatgpt5. Or use Claude.

Duration: 20 months ≈ 87 weeks. Mon–Wed evenings: 3 h (4–7) — nod only → 3×3 = 9 h/wk Thu evening: 5 h (4–9) — nod only → 5 h/wk → Weekday evenings total (nod): 14 h/wk Fri & Sat: 10 h each per person → 20 h/day combined → 40 h/wk Sun: 8 h per person → 16 h/wk → Weekend combined: 56 h/wk (28 h each) Regular week combined: 14 (nod) + 56 (both) = 70 h/wk 4 weeks annual leave spent on site: assume both worked 10 h/day Mon–Thu as well as the usual Fri–Sun → Per person in those weeks: 10×4 + 10 + 10 + 8 = 58 h/wk → 116 h/wk combined No holidays except Christmas Day & Boxing Day: subtract 2 days ≈ 40 combined hours (10 h per person per day). Calculation Regular weeks: 87 − 4 = 83 weeks Combined: 83 × 70 = 5,810 h Annual-leave weeks: 4 × 116 = 464 h Subtotal: 5,810 + 464 = 6,274 h Less Christmas & Boxing Day (~40 h): ≈ 6,234 h combined Split by person (after subtracting holidays) Nod: (42 h/wk × 83) + (58 × 4) − 20 ≈ 3,698 h Mrs Nod: (28 h/wk × 83) + (58 × 4) − 20 ≈ 2,536 h Answer Total hours on the build (both together): ~6,234 hours or around 890 days (assuming 7 hour day). Roughly 3,700 h (nod) and 2,540 h (mrs nod) Does this look right? If it is, on an average day rate of £225 it’s around £200,378 you’ve saved (£586k total - ~£1400 per sqm for an effective build cost). @nod - what did that cover out of interest? Was that all your materials, decoration, landscaping etc? Does the 420m2 include your garage?