JohnMo

Fan coils work well for cooling and heating, but as with radiators they need to be sized correctly for the heat loss first and then for the cooling load. So you need proper room by room heat loss calculation. You basically set the cooling flow temp to match output needed. That flow temp for cooling can be anywhere from 6 degs to 20. The fan coil fan speed modulates to match output needed in a micro scale. Running cooling below about 14 degs required condensate drains at the fan coils.

Jotun https://www.rawlinspaints.com/products/994-jotun-penguard-express-zp.html?gad_source=1&gad_campaignid=23257329793&gbraid=0AAAAADwqu94V43vCFb8yzShst-tZZva6u&gclid=Cj0KCQiA1JLLBhCDARIsAAVfy7h-TKMmfT5USzPcfuXTp4QE_N1p81iHyvb7ZFyBlLtiTim2umqRhRIaAsTlEALw_wcB The linked is a high since phosphate epoxy primer, can be applied with paint brush or roller, even though the instructions say to spray paint. Epoxy isn't that UV stable, so would need a top coat. Prep to give it nice rough surface to put on to, then it's there for life and stops rust well. I used on a 50+ year old Beetle floor pan, 12 years ago, still looks like the day it was painted (not been on salty roads though)

Hot dip galvanised? If installed maybe not. Best coating by far is Epoxy, not cheap, but great.

That isn't good enough for a heat pump, you need an accurate assessment. My house is 192m² all vaulted ceilings (225m² including plant room) my heat loss is 3.5kW at -9. Just about to remove a 6kW heat pump and install a 4kW one. Not the correct way to go about heat pumps. Not really correct for has boilers either.

That is one huge heat pump - are sure you will ever need that big? Oversized heat pumps are not good. Correct sizing is important. Integrated systems are almost never needed. Keep ventilation separate from heating. Don't waste your money, heating is only good for 10W per m² of floor area, cooling via MVHR is crap in the UK due to low flow rates and humidity. Just use a normal heat pump cylinder (more later) Yes, but choose based on actual heat demand at -3 (location depending) and more importantly min modulation at 7 to 12 degs. Work out heat loss at these temperatures and choose a heat pump that will modulate down to that level. Home automation - just isn't needed. So system layout PV and battery let them run on their own, supplying house and export excess. Keep it simple, no integrate quired it's there by default. Heating, fan coils is fine for heat and cool. But again keep it simple. Ventilation IF you are airtight better than 3 and are strongly making airtight decisions then ok. Just have it do ventilation nothing more nothing less, it runs in background 24-7. DHW, you can have ASHP do hot water, if so just choose a cylinder with a 3m² coil. Or heat during off peak periods via immersion, with solar real cost difference is that big. I have run every mode of heating control with a heat pump and weather compensation wins, on comfort, costs and ease of implementation. No third party control is needed and adds to running costs. It run priory hot water mode, it just switches from CH or cooling to DHW. No issues. No your just making it complex in your heat, each is a separate standalone solution that without the box without over engineering Battery and PV work out the box Ventilation set and forget (except filter changes) ASHP set WC curve, get on with your life DHW either set a stand alone immersion timer, or get the ASHP to it via a schedule.

ToU tariffs have existed since the 70s (E7 etc) so no idea why they will just disappear. Format may change, but that's life. Have managed the battery in simple E7 and now Cosy.

I would buy a long small dia drill, that can go through the whole lot, drill to give the fall you need in the duct. From there you have a centre for the duct. Mark up the diameter you need. Then drill a pilot hole and use a jigsaw to take out the hole, repeat on the other face.

All I know is from my own perspective, I almost never pay more than low rate Cosy even when its -5 outside. That's with a 13kWh battery and cosy tariff. (So 15p per kWh).

I think I would step back a little First decide what your running logic is for the immersions. Are they all switched together, one heating at a time etc Then test is that the right logic to take - is too simplistic or just way to complex to make sense for anyone else to try and fix it etc. will save you energy, will things fight each other etc Then when that is all making sense, plot the best control approach and from there how best to configure the wiring.

That's the smart solution. If you put it in a bag you will soon learn all about it. True, about the same as 20mph wind, hitting all sides of the building at the same time.

Wouldn't want to have my heating system reliant on so called smart stuff, use something that has internal control for time and temp, that can be accessed remotely. Keep it simple. Then should you loose internet, or home assistant switches off or doesn't want to play, it all runs regardless. I dabbled and nearly had my head on a spike.

Although 3kW is a 13A draw, you would really need 16A switching for long term reliable operation. Why do you need 3 immersion heaters?

When I was screwing into stuff I put a blob of hybrid silicone stuff on the screw. Whether it made any difference who knows? Once a screw is in the wood the wood contracts around the thread, so I doubt there will be any leaks anyway. Ours aluminium faced so used aluminium tape to cover all the staples.

I asked AI got this answer when asking about graphite embedded in EPS insulation Value is added because the "air space" required for graphite to reflect radiant heat is actually located inside the material itself, not as a separate external gap between the insulation and the concrete. 1. Internal Reflection Within Micro-Cells Graphite insulation, specifically Graphite EPS (GPS), is composed of individual closed-cell beads. Even when tightly embedded in or under concrete: The "Air Space" is Internal: Each bead contains millions of microscopic trapped air pockets. Infrared Mirroring: The graphite particles are infused into the walls of these tiny internal cells. As radiant heat attempts to travel through the board, it hits these graphite "mirrors" and is reflected back and forth hundreds of times within the cellular structure. No External Gap Needed: Because this reflection happens at a microscopic level inside the insulation board, the board can be in direct, "intimate" contact with concrete without losing its reflective benefits. 2. Physical and Efficiency Gains Even without an external air gap, graphite adds measurable value over standard white insulation in concrete applications:

Doubt in an UFH system. There is no space for radiation to occur.