ProDave

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.

Yep, if no services, put the PB straight onto the PP board without a gap. Gives you a little more heardoom.

post the details of the exact thermostat.

Surely a utility room will have a sink unit or something, put the odd ones under there?

You should have counted how many you had before you started that room.......

Tile the WHOLE utility room different. Keep the rest of the white ones as spares for the other rooms.

We have a petrol leaf blower. It can also suck and act like a big vacuum cleaner sucking leaves up into a bag. That function is handy for clearing out gutters and drains, but not of much use for general leaf clearing as it would be soon overwhelmed.

Heating the hot water will heat it hotter than the ASHP so there will be more expansion. But that should not be a problem. You have two expansion vessels for the hot water, I only have one, and my single expansion vessel is still working fine. If you wanted to keep the 2 old ones you could refurbish them with a new bladder in each, or even ask they guy if he would replace the bladders for less than the cost of replacing the whole thing?

Okay progress. We know the hot tank is over pressurising when the water is heated which does indeed usually indicate the expansion vessels(s) have failed. I am a little surprised as there are two of them so would expect them not to be particularly stressed. This is not something to ignore. You have to trust your gut feeling and get the person that quoted to replace them or a different plumber that comes trusted or recommended by a friend. This does not need to be a heat pump plumber as these expansion vessels are the same regardless of whether it is a heat pump, gas or oil boiler, or just plain direct immersion heated. Switch off the solar diverter for now and only heat the hot water occasionally as needed using the heat pump to heat it. A lesson here is be there when the next plumber comes so you can engage with them and when they find a problem like this they can probably show you what they are testing that made them conclude they need replacing. One would hope they had de pressurised and concluded the air bladders are burst and they would be able to show you. EDIT: to add to the above post, if you have a car pressure gauge and a bicycle pump we could talk you though checking the pressure to be absolutely certain if they have failed or just not enough pressure in them.

I very much doubt you will get two 10mm cables into one of the terminals on one of those. Is this a (home made?) storage boiler? the commercial ones will have one high power feed to a control box and typically use a contactor to switch each element.

Before you make the choice, price up all the options. Frametherm is so much less nasty than most wool insulation and it is quite stiff so when pushed in place it should stay there while you get the netting etc in place, many will just fall out. https://knauf.com/en-GB/p/product/frametherm-r-roll-35-ready-cut-26329_4206 Search for best price, I got mine from SIS as they were the cheapest I could find it at the time.

4" will be a lot better than nothing. It will be a miserable job from below you will need full suit and respirator imho. Use something like Frametherm 35, a lot less nasty than most flavours of rockwool style insulation and quite stiff so should push into place and stay there while you get the netting in place.

Where I worked before they built a spiral staircase. The plasterboard was stood against a wall outside and wetted frequently and gradually it curved under it's own weight as it was leaning against a wall. After several days it had got to the approximate bend radius needed so it was brought inside and wetted further and gradually eased into the bend needed. Once to the radius you need you let it dry before you screw it to the wall. That is a job well suited to DIY as it will take time and your own labour is free.

More information on what wall finish you have, and what sort of access panel you want to make.

He says he topped up the glycol levels so that makes sense.

Yes that is the tundish. It should remain bone dry. IF any water passes through it would pass on the inside, it is just there so you can see if anything is passing through. You could try rolling up a bit of tissue or toilet paper and sliding it into the space inside. That will show you if there is any discharge even when you are not watching it. It that remains dry over a few days as you use hot water and it gets re heated, then there is nothing wrong with the white expansion vessels.

"servicing a heat pump" might be slightly specialised, but just about any plumber should be able to do all the normal things related to the rest of the system like expansion vessels pressure checks etc. Those would all be the same if you had a gas or oil boiler as the heat source. So it looks like the red heating expansion vessel is okay. Just the 2 white ones to check. Can we have a photo of the pipework under the tanks? We are looking for a Tundish that will look a bit like this When you find something like that, have a close look at it. If there is a problem with the 2 white tanks that the plumber wants to change, then whenever it heats the hot water, you will see water dribbling down the inside of this. It should be bone dry normally.

I had similar with the flashing for my stove flue that bent up one corner in a storm. My repair was to bond it down with appropriate goop. Has not happened again.

Why not dig up the flower bed, install a proper soakaway under the flower bed then put the soil and plants back?