ProDave

DO fit the safety thermostat. What if the HP has an immersion built in that it uses as backup? many do? What if you have an immersion in the tank itself?

Following with interest. One of the things that bugs me about heat pumps, is there is no standard for how you wire them. Mine, an LG needs a LOT of individual connections to the heat pump itself. It looks like with yours all those connections go to this indoor box presumably connected to the outside unit with a simple cable. It makes swapping from one heat pump to a different make a lot more complicated.

The tank WILL stratify. Not so much when it is being heated, but as you draw hot water it exits at the top and is replaced by cold water entering at the bottom. Those don't mix much so the hot / cold transition just moves up the tank. So you want the heat pump probe, the one the heat pump used to measure temperature in the lowest pocket available, so it detects the cold water as soon as possible and starts re heating. I initially tried mine in a higher pocket, and the tank did not re start heating until half the hot water had been consumed. The immersion heater one? Are you talking about the safety thermostat part of the cylinders safety system? I have that in the higher pocket. this is the one that is supposed to shut down the heating demand and close the motorised valve to protect from a runaway out of control heat source.

Looks hopeful. Can't wait for your later update.

The AC/DC thing. Volt drop in AC is critical, with PV it manifests itself as voltage rise, i.e. the voltage at the inverter will be higher than the voltage when it gets to the house. Now most inverters have an upper limit where they will limit power output or shut down completely. This is typically 253V. If your grid voltage is already high, there might not be much tolerance and the inverter may shut down often. Voltage drop on DC will still give the same power loss but is very unlikely to cause the inverter to shut down, so does not cause much of a problem.

Yes it's a long standing known problem without a sensible off the shelf solution. All I could find was a very few fire rated outside doors (it does not need to be weatherproof) at a high price and you still had to fit the closing mechanism yourself. I ended up fitting a standard FD 30 door, making the frame a good fit and adding a draught seal in addition to the intumescent fire stop seal. It is not perfect and no doubt the source of some heat loss and definitely the source of a bit of a draught, but I took the view the small heat loss would just add a little heat into the insulated garage.

We don't know much about the house, but I would deduce from the floor plans, the lack of windows in any of the ground floor rear wall, and doors from the first floor rear wall to outside, that the ground floor is set into a bank. So if you divide the garage as proposed, there will be no prospect of creating a separate door from the pool room to outside. A door via the WC or just in front of the downstairs WC might be possible. I also suspect that once you have divided the pool room off from the rest of the garage, what is left won't be long enough for a car to fit it. So if you decide you are not going to put cars in there, then it might be better to convert the room as a whole to something else?

I may be wrong but I would expect a 3 phase meter to have 3 metering coils, one per phase. It would then be up to the software how it combined them. The old spinning disk meters could do nothing other than net metering, even going backwards unless there was a ratchet mechanism to stop that. From a legal perspective you might expect an electronic meter to give the same result as a spinning disk meter ?

What stage of the build are you? Why not put the VCL across the top of the joists? Or as above slim downlights. Some will literally fit in the thickness of plasterboard.

So are ALL 3 phase meters installed now "net metering"?

I posted a while back that the national grid operator has declared there will be no more wind farm connections to the grid in Scotland (after the ones already scheduled for connection) until at least 2035 and that more wind farms are needed in England and Wales. We just need that implemented in planning policy because planning applications are still being decided for wind farms near us. If you try objecting on the grounds they will not get a grid connection the planners say that is not a planning matter. As usual no joined up thinking. If a grid connection is not possible, then planning should not be possible. Unless you want a load of wind farms built and probably paid some form of compensation for not generating because they cannot get connected?

This for me is ringing alarm bells that it is NOT the white water expansion vessels at fault. If it were then the tank would be discharging on over pressure and that would be 45 degree hot water from very near the top of the tank. I would still want a plumber I trust to test everything and find out exactly what IS at fault. One thing I did when plumbing my own system is I fitted a pressure gauge on the top of the hot water tank so I can see if it is over pressurising. That is not normally done, but I had one spare. Perhaps when the guys come with their new white expansion vessels you can agree with them, if this does NOT solve the problem they will fit the original ones back and refund that cost? It is sounding to me like "fault finding by substitution"

Are these houses being lived in, or is it as the website suggests a "home exhibition"?

No need for earthing but you will need an enclosed terminal box for the mains connection not just a pair of naked wago's. I would also use an enclosed junction for the DC connections.