ProDave

I hope the Llangollen is staying where it should be and not trespassing on your garden.

Simple answers yes yes and yes. If you are having all UFH then perfect. An ASHP will heat DHW in an unvented tank, avoid a thermal store, they need water stored hotter than an ASHP is comfortable with. Most of us heat the DHW to about 48 degrees which is plenty hot enough for use but not as hot as a gas boiler would go, so we tend to use a slightly larger HW tank. Don't order the ASHP until you have a proper detailed heat loss calculation so you know it is sized to the size and insulation of the house. they WILL be lower power than a gas boiler so it is important to get the size right. Mitsubishi Ecodan is a popular choice and not over expensive and I have not heard anything bad about them. There is the "discussion" whether to get an MCS install and claim the RHI, which might not be very much for a new install, and might have finished anyway before you get there, or just buy it and get your plumber / electrician to fit it. If you are thinking of using it for cooling, as well as the UFH you might want to consider a couple of Fan Coil Units mounted high in the building to deliver chilled air (just like an AC unit) which is more likely to chill the whole house than just running cool water through the UFH.

Nothing has "priority" you are over thinking it. The inverter will spit out as much power as it is able to depending entirely how much sun is shining on it. Your house will use as much energy as ANY appliance turned on needs to use. If generated power exceeds power being consumed, then to prevent power being wasted exported, your device will send that power to the immersion heater. It can send anything from a few watts up to the full nominal 3kW to the immersion heater. In the winter the heat pump will use almost all that you generate, but even so, there are times when it is idle and I have seen power going into my immersion heater. The appliance thing is more for the summer, when you are generating most PV power but apart from DHW heating, the HP is not doing much. I have my HP timed to not start DHW heating until 11AM by which time there is a fair chance the PV is generating a good amount. But we also use the 3 big appliances one at a time around the mid day slot to try and self use as much as possible.

Yes that is the whole point, they only send to the immersion heater the excess power that would otherwise have been exported. The best use for solar PV is to use it for something more useful, like do all your washing, dishwashing, tumble drying in the daytime close to mid day one machine at a time.

Have you tried turning off all but one radiator and seeing if just 1 radiator running will reach 55 degrees? Or am I wasting my time trying to help?

Hello, yes Flat 1205, 12th floor, can you come and service my air source heat pump please?

For me the disappointing thing in the wish list is the air test number. I see SO MANY houses, even recent ones where you unscrew a socket from the wall and a howling icy cold gale comes out of the hole. It is my gut feeling that the best "bang for your buck" improvement would be force the builders to sort out the air tightness and install mvhr. The air tightness is not so much of a cost issue but an attention to detail issue.

Just one or more 16A sockets. Contractors will bring their own 110V transformers. As early in the build as you can makes sense. And remember to give the site sockets their own TT earth NOT a PME earth.

I will stick to my boiling water tap.

I am 5 years into my build and nearly finished.

Welcome back. You see the self build bug is adictive. They say you probably get it nearly right by No 3.

Thanks @newhome

Back in the day, it was a trademark of a BR craftsman that all the screw heads were lined up. Of course the engineer would argue by doing that they cannot possibly all be tightened to the correct torque.

See my post earlier. Turn off half the radiators and see if the ones left on get properly hot. That will start to tell you where the problem is. Or even more extreme, turn them all off but one. That one left on should have no problem getting properly hot. If it still does not then something is set seriously wrong with the ASHP. If that one radiator gets properly hot, turn on another. do they both get properly hot? If so turn on a third and so un until you reach the point they can't all get hot. Report the findings.

35 degrees is barely tepid. I would have expected radiators to be running certainly over 40 degrees. If that is the hottest it can get them, it rather looks like the HP is struggling. Turn half of them off completely and see if the half left on get any hotter than that. The small difference between input and output is because they are so cold barely any heat is leaving them into the rooms.

Jewsons do a trade account for self builders. The only reason I had one was they were going to slap a delivery charge on for cash sales. I can't say it made much if any difference to prices.

Who built the house or have you just bought it like that "unfinished"? What is the sides and top of the recess made of, looks like plasterboard to me. Normally you would have a stub of flue pipe and a register plate, but I am not yet convinced that lining is fireproof, and I would have expected the flue liner to be encased in insulation like vermiculite but there is nothing to hold it in, so I suspect not. I would be having words with the builder.

I would love to see a description of what an ASHP "service" actually is or hear from someone who has witnessed one done, as to actually what they did. All I can think of is a visual check to make sure the air flor is not blocked, a functional check, and check the pressure in the heating loop (though the latter is not really an ASHP service) Snake oil springs to mind, but I am a suspicious person.

Does the drawer close? If so that should do nicely.

An inward opening door is a flawed design for a door facing the prevailing wind. On a windy day you will not stop some water getting over the drip beads and finding it's way into the gap between the door frame and door at the bottom, with the only thing holding it back being the seal. Even if the seal is perfect, there will be a little bit of water sitting there, just waiting to come in when you open the door. Ask me how I know.

If this open fire proposal is for a new build, do come back and tell us what building control say and if they pass it please.

Would it even be possible just to drill a hole in the bottom of the existing thermostat housing so that just pokes out the bottom? That would be a neat solution.

The counter argument, is a gas connection comes with a cost, the gas work must be done by a gas safe engineer with a cost, there is an annual service with a cost. On the other hand many of us have sourced our own ASHP's and self installed them for less than the gas connection would have cost, even if gas were available. I accept if you have gas then a gas boiler will be the cheapest system, but for those that don't have gas and can't get it, an ASHP is far more attractive than other alternatives.

Toilet cleaners are okay in small quantities as are normal detergents etc. Don't put anything down the toilet that has not been eaten first.

That should not affect the HP settings but it will affect the immersion wiring and may mean the immersion can no longer be controlled from the HP.