JohnMo

PV and immersion heaters isn't as straight forward as DC to the immersion as the impedance (think that's the right term) needs to be balanced You need to use something like the attached spreadsheet to calculate the match between panels and immersion. Or as @SteamyTea say, go AC and then diverter. Solar PV Calculator (1).xlsx

Different for hybrid or non hybrid. G98 approval allows 3.6kW export with prior approval, so you would overclock the inverter, have more kW on the panel side, because 99% of the time it will not be at nameplate rating. So 3.6kW inverter with say 4kW panels. When you get to hybrid, the kW rating also applies to how much kW you can transfer from battery to house. So here it's better for a bigger inverter. But then you also need G99 approval. Horses for courses.

We have found with UFH in the heating season, because the floor isn't sucking so much heat away, the rooms actually feel warm with the thermostat set at 19. But when the UFH cooling is on, even though the room can be 23/24 it actually feels nice and cool.

I bought my GSE trays from ITS, they were £25 each. I would double check your quantity of the sundry bits from GSE. £98 for each panel doesn't sound right. Here is my list of bits for 10 panels

You just balance, if one area is too hot decrease flow to those loops, if to cold increase flow. Adjust over a week or so. Have a wireless thermostat so you can use trial error to find the best location. Use it to control the whole zone.

All nicely symmetrical, except the one landscape panel, which I would omit. I take it they are smaller panels also Would suspect you are too close to the edge on the outbound corners, because you need tiles for the ridge tile to sit on and have correct support.

Obvious question is why do you have to fill your roof, if your not careful it will just look like the dogs dinner - a mess. Are you just trying to be too greedy? If it's not symmetrical and balanced it's not going to look right. What about 2 rows of 450W in landscape under the roof windows, that would give 16 panels or 7.2kW. Adding more may sound good - but if your sketches are anything to go by, it looks a real mess.

Look at my links a couple of them are tray less

Have been on here, there are config tools to download. https://www.gseintegration.com/en/solutions/gse-in-roof-system/ This is different in roof system https://www.viridiansolar.co.uk/solar-products-roof-integrated-pv-fusion.html And another https://www.wienerberger.co.uk/products/roof/in-roof-solar.html Possibly another https://www.roofingsuperstore.co.uk/product/marley-solar-roof-tile-portrait-roofing-kit-left-top-corner.html?gclid=Cj0KCQjwi7GnBhDXARIsAFLvH4lddduw6y1mB25gKev7SyPxJEEhMx-gKHn_mEW3jpf63abG9qky35YaAluWEALw_wcB

If not fully rectangular are smaller sized panels easier to make fuller use of the space. If rectangular big panels full fill the space. Base the design around the GSE tray formats available and any curbs required that suit your sizes, then find PV panels that fit the tray.

Really, why would you actually bother importing, with a organising, shipping, getting the goods in the country, import duty, getting goods to your house. What about warranty - not worth the paper it written on. To save pennies, or most likely pay more when all said and done, just select from a good priced wholesaler in the UK. Open a account with a decent sized wholesaler in the UK, go into a local store, tell them you would like to order xyz and looking for a good price, they are likely to beat any internet price. If they don't move on the next company.

If you flowing at temperature that cause manifold condensation you are flowing at temps that will cause floor condensation - which is something you need to avoid. A PIR box is easy to do. Even easier if you have no pump mixer or zone valves. As no reliability issues to consider by boxing in and trapping heat.

Ours is similar to the above photo. We were told the first x number of meters is to be completed to roads spec, as vehicles/lorry's are allowed to part there while offloading etc. Anything else inwards from there, you can almost do what you want, but has to be SuDs compliant. Also because our access is sloped down towards the road, we had to have a linear drain and suitably sized soakaway to prevent water our property entering the road. The council will have a standard set of details they will expect you to follow so the entry complies with whatever roads rules there are. Single track roads are treated very different from dual roads. As I believe a single track road has in effect to form a passing place for other road users

Grant also do a two port one that is designed to be mounted outside on the ASHP feet. It has an immersion inside also. Just read the last sentence in the above reply which says the same

Use DeWalt aircrete fixing, easy cheap and fix really well.

Not sure that would work really, the other heated areas heat would just leach into the unheated room, if the fire off making heating the whole building worse. How long do you run the lounge rads for per day? The rads should be matched to the heat loss - no matter what the heat loss is. Anyway it is so unlikely that any manufacturer would agree to a retrofit partial install - it's just a waste of time suggesting it. More stress when they say no!

That's my current plan, fairly flat WC curve, 0,1 hysteresis thermostat set 0.5 degs below target temp. Set WC to allow a 5 to 6 hrs slab heat time at start of heating season and about 8 to 10 hrs at the lowest likely temp. So most electric usage coming from off peak E7 and if required draw on the battery in the day. That said if you have a decent screed depth it works a treat. Last 2 years with gas boiler I tried every option going (will try same this year on ASHP), recording boiler efficiency and gas usage etc. Batch heating overnight worked really well. Stable room temps, lowest gas usage of any heating pattern tried, basically flowing approx 35 degs (weather compensated) for 6 to 10 hrs overnight. So on for 6 to 10 hrs off at all other times, long run times, long off time. Found switching the heat off 0.5 degs below your target temp allows the final heat to percolate through the floor and not have any temp overswings

My unit although on a stud wall, I lined the wall in 2x layers of 18mm ply, which seemed to work well.

That being the case, he cannot expect that much better CoP. If an MCS install, all the expected efficiency, design temps and running costs should be laid out. If performing worse than that, something isn't right. If running as per those figures he getting the expected results. But cannot see why an MCS install would be in the mid 2s CoP.

My manifold sits in a cupboard and the heat given off warms (doesn't make it hot) the cupboard, used for storing bed linen and towels etc. They give off very little heat as the flow temp should only in the high 20s most of the time and early 30s if really cold outside. Even in cooling duty the condensation is nil with a flow temp down to 11 deg. If you were installing UFH in an old building and flow rates were 40+ all the time, the story would be different. Really wouldn't waste your time effort.

Thread is talking about a house, but if it requires planning, it needs a structural certificate I believe. Scottish say they want independence, but everything in Scotland tends to be different already, planning rules, building regs, laws, education, health, police, tax rates, fire service

Or for a complete answer, if you live in Scotland, where you need a full structural engineering certificate prior to Warrant issue.

Too busy faffing

Or fan coil unit, for heat and cool. Make best of CoP and cooling ability.

With poor insulation under the UFH pipes you will spend as much heating any void below or ground below, as you do heating room. Plus with an insulating screed your flow temps will need to be high also and on for a long time to have any effect on the room, so it's a loose, loose situation. Your ASHP flow temps will be set to manage the floor heat loss of your garage, so CoP will be way worse than its needs to be. Electric heater on 20 to 30 mins on to heat room, then click on off using next to no electricity.