SteamyTea

Bargain for a 500 MHz machine.

@Nickfromwales, @JohnMo Are accumulators basically maintenance free, maybe not quite fit and forget, but close to it?

Was it something like this? https://www.heatershop.co.uk/stiebel-eltron-dce-x-10/12-premium-238159-single-phase-instantaneous-water-heater-4i-technology

Convert the RH to AH and see what you are really dealing with, it may only be a cupful of water in reality. https://www.lenntech.com/calculators/humidity/relative-humidity.htm

Was it meant to look like a cheap kitchen swing bin?

Ask @joe90 what he bought, then sold as it was not needed. I think his one modulated with regard to inlet temperature.

I have not read all this, I got depressed when I saw 50mm insulation. You may well be needing heating upstairs with that small amount. A secondary point is that UFH can also be used for cooling, not ideal in a bedroom, but may be useful. With only 100mm of ground floor insulation, I would be looking to fit radiators, they are going to cost less to run.

Fan assisted rads maybe, especially if they can be got a decent price.

You could fit a couple of supplementary inline water heaters, say one on the least used shower and one on the most used shower. Might be cheaper than plumbing in an extra cylinder.

Your new glasses are working well then.

This caught my eye. "radical new design ends the world of 'ugly heat pumps'". Bet the ."as hot as a gas boiler" uses a resistance heating for the last 15°C when needed.

I am currently reading this. Should put you off starting, which is the best place to stop.

Shows I can bull shit with the best of them still. I was thinking that it may be worthwhile knocking up a very simple spreadsheet that does a sanity check. Or if there is a clever person on here, a web based one.

Both, and a UV system as well.

I don't know, how close? It is always worth doing a simple model as a sanity check. Then do the detailed one to set emitter sizes for different room temperatures.

I think you have, 50 kWh would be more like it, though that would be a very large, and heavy, set of lead acid batteries for a fork truck. Maybe they said 50 Ah. Lead acids used to be the cheapest mass energy storage, though I suspect second use lithium's are cheaper now. Lead acids take looking after, but nothing wrong with them.

Probably an 8 kW model is needed. Most of the time it will be fine as it will not be -2⁰C outside, more like 5 to 10⁰C, then the heating is off. Are you fitting MVHR, if so, your air change losses will be quite low, as long as you get your airtightness good. As others have said, how often will you really be running 4 showers at the same time? At 10 litres a minute, with 4 showers running, a 300 litre cylinder would be empty in about 10 minutes. Actually if it was stored evenly at shower temperature, the 7.5 minutes.

First things first. An ASHP and PV are rated by power, the kW. You buy electrical energy by the kWh. As for the best tariff, hard to say. Do you know the amount of energy your ASHP has consumed, the kWhs, and what your PV has produced, kWhs again. Do you also know the shortest amount of time you can run the ASHP for to get a day's worth of energy into the house, I am assuming you have UFH in a concrete slab. What is your DHW usage.

I have never had much luck filling over foams. I think it is the greater thermal expansion rate of the foam that causes the problems.

Yes. I should have said it was per degree difference.

That would only be another 600 W.

I just quickly modelled your house as a simple cube. 12 m long, 10 m wide and 5 m high. Came out, as 292 W/°C at 1 ACH. So at a delta of 20°C, that would be 5831 W, at 23°C, 6705 W, or 6.7 kW. Have you mixed up some units somewhere i.e. metres and feet.

It does, press and hold the zero 'key', the ⁰ symbol will reveal itself.

Just to clarify something. ° is for degrees. ' is minutes, a 60th of a degree. I degree. °, is 60 minutes,'. And, just to be a pendant, 3600 seconds, which has the sign, ".

We have Arthur C Clarke to thank for that. Rendezvous with Rama