ProDave

That explains something I think. I have been using the external room thermostat input right from the start, so have the traditional thermostat per room connected to the UFH manifold control box and it is the call for heat contact from the manifold controller that goes to the ASHP "room thermostat" input. I did once try playing with weather compensation and got a very odd result, it switched the ASHP into cooling mode. At the time I thought I must have miss understood the settings and just put it back to normal. Mine is an older version than most on here so has a different controller and none of the parameters were greyed out, but perhaps with the room thermostat input enabled they just don't function or at least not as expected.

Also on the subject of pulling the main fuse. ONLY consider it if it is a modern all plastic fuse carrier and base and in good condition. There are a lot of old damaged main fuses still in use and some really lethal metal cased main fuses that even the DNO don't like pulling I would never touch those.

Simple. You run the ring main cable, and a bunch of tv coax and network cables all the way around the room horizontally at 450mm above finished floor level. You need to put 1 socket on each wall, at a place you either know is definitely where you want it, or will be hidden. That creates a "safe zone" for the horizontal wires to run in on that wall. Then, when you know where you actually want sockets, you cut holes in the plasterboard for the socket boxes and fish out the cable that is waiting for you. You will need to leave some slack in the cable of course.

Not necessarily, SSE allow electricians to pull their main fuse, but that was not often needed as SSE also used to fit meters with a built in isolator switch, these are now systematically being replaced with smart meters without such an isolator.

And as any electrician will tell you, they chose NOT to use that in built facility to allow electricians to safely isolate an installation. My present dumb meter has an inbuilt isolator switch, another reason I would like to keep it.

Yes you can, just make sure it's a separate inverter and not connected through the FIT meter, so you have not altered the original FIT kit.

That estimates a waste water temperature of 27 degrees. My point above is I would be very surprised if the actual water going down the plughole is that warm after the room and walls / tiles have taken some heat out of it.

You will need a pan connector anyway to fit into the soil pipe, so you might try an offset one like this It would in effect increase the depth of the U bend in the WC and still leave the outflow going down hill. No doubt a plumber will come along now to say why not, but I did this years ago in a previous house to line up with the outlet that was a cast iron pipe cemented into the house wall which i did not want to replace.

or go back to the original plan of tiles?

Yes is is surprising how light and strong "caravan" furniture can be. I think "stressed skin" is the design principle.

No government body dare talk about the elephant in the room. just what do do about all the lousy leaky houses in the UK, how to upgrade or replace them, and who will pay? Easier to bang on about wrong door colour.

You mean the soil pipe is already higher than the pan connector? or are you saying you "only" have a fall of 15mm over 200mm?

How many extra SAP points would an extra £800 of PV add?

That is the bit that is not making sense. The actual immersion heater is nothing special, it is a waterproof resistor. Changing it will do nothing. What you probably mean is if the immersion heater is connected to another controller e.g. for a backup or a periodic high temperature cycle then yes there could be a problem, so why not just disconnect it from that controller, it is probably not needed anyway, and just connect your diverter as the only thing connected to the existing immersion heater?

This water heat recovery thing. When I have a normal length man shower (could be different for a long lady shower) when wiping down at the end, I find any water left is "cold". My assumption being most of the heat in the hot water has been absorbed by it landing on the "cold" (room temperature) walls and floor. So most of the heat is being absorbed by that, later to be released back into the room. It would be interesting to lower a waterproof temperature probe into the shower trap and read the actual temperature of the water reaching the trap. My suspicion is it will be a lot lower than the shower water temperature, so any theoretical heat recovery will be less than expected. Like @SteamyTea I would like to see data.

My understanding is most heat pumps only heat DHW or space heating (UFH) at a time, never at the same time, so is the diverter valve playing up? Could the fact heating or DHW work fine on their own confirm that?

That does not explain why my use is steadily dropping. Perhaps nagging the kids to not leave stuff on standby is working? PV generation is slowly improving year on year, the tree pruning is helping there I think.

I read my dumb meters once a week and log the readings on a spreadsheet. I am managing to reduce year on year consumption every month.

THIS is the misconception. You are not looking at your "smart meter" you are looking at the In Home Display unit. That happens to be something you get with a smart meter, but that is not THE smart meter. You can have such a device with any meter. I bought one for about £5 to show instantaneous usage, but it turned out to be useless as the particular one I bought could not cope with solar PV and an excess PV dump controller. IF getting people into the habit of watching what the IHD says and reducing your usage was the goal, that could be achieved without forcing everyone to have a smart meter. Just supply an IHD to everyone but one better designed than the cheap one I bought that does not cope with bidirectional energy.

That is because, at least to start with, the tv advertising was openly saying "get a smart meter to save money". I and many thousands complained to the ASA about this false advertising, but nothing got done. Or perhaps it did? there is now the very small print saying something like user action is required to save energy usage. In other words read your meter to see how much you use and if the figure shocks you, use less. It is NOT the smart meter that makes you do that.

A big rump of the population (me included) don't want to play the silly variable priced electricity game and have to choose each day what time to turn the oven on. That is in part why a lot of us are resisting having a smart meter for as long as possible.

What is the application? Why light weight? Boat or caravan?

A small turbine is something I am still thinking about. Everyone says it will be disappointing. But I still feel I want to play with more types of renewable power and an tempted to take a punt on this for not a lot of money. https://www.vevor.co.uk/wind-turbine-c_10731/vevor-wind-turbine-generator-kit-12v-wind-power-generator-300w-w-mppt-5-blades-p_010372870276 I am sure someone will be along to dissuade me.....

We have been obsessed with CO2 reduction for some time, and not been watching fundamentals. Closed all our coalmines, closed all our coal power stations (though one still burns wood and thankfully a couple have not been decommissioned so can be re started and still used) We are building wind farms as fast as we can but we all know they need wind, that does not always blow. This created the "dash for gas" as burning gas to produce electricity is a little less harmful than burning coal. Great. Except we don't have enough of our own gas. No problem, we live in a global economy now, we can buy anything from anywhere, why bother going to all the trouble of producing something ourselves when someone else will make it or produce it and sell it to us. Oh look those Ruskies have a lot of cheap gas and they are even building a nice big pipeline to deliver it. What could possibly go wrong with such a global trading situation? Oops. Someone forgot to think about "Energy security" let alone security of anything else we import, like food, certain high tech products like microchips, even steel and other raw materials. Oops indeed there are very few things now that Europe is self sufficient in, let alone the little old UK. Now our government is talking about drilling for more gas in the North Sea. About time but will take some years to come on stream. Lets hope the environmentalists don't stop that as we are really stuffed if they do. Re the forecast power cuts. They will be a nuisance. I don't see they will actually save very much power for the average domestic user. We might get a few hours power cut, they don't predict how often, but apart from not being able to watch the telly and the lights will go out, that is about all it will save in terms of power. The fridge will warm up a little and use the same electricity when it comes back on to cool down again. Heating with an ASHP, the house might cool down slightly, but hardly measurable, and the ASHP will fire up again later if it needs to when the power comes back. If there is really more demand than supply, you have to remove demand, which really means industry, which means not making things that take a lot of power to make. I know, lets just buy those things from abroad instead..............

Just a thought, is it the local pipework under each sink has got smelly? This happens sometimes e.g in a dual bowl kitchen sink where one does not get much use. A little bleach down the plug hole cleans it up and stops the smell. If the vent pipe goes out through the roof and finishes a little way above the roof, then you may not have an AAV as not always needed.