JohnMo

Except in Scotland - today we are being provided by 100% wind, but at gas prices

Your other issue is the immersion is at the bottom of the cylinder and the probe you are showing isn't at the same elevation. So the immersion and the probe are reading different places in the cylinder, so will see different temperatures. Slip it back together and get on with other stuff. You temperature probe is just a variable resistor, it either reads or it doesn't. It's pretty black and white. As @JamesPa says hold it in place with some insulation, it will read more realistically, as you don't get cool air drawn into the cavity.

ASHP temp sensor is what you have in you hand. It works with ASHP controller to tell ASHP to heat the cylinder. The immersion has its own thermostat under the white cover, it also has a safety thermal cut out, to stop the cylinder boiling if the immersion thermostat fails. If you are heating via immersion the cylinder will heat to whatever the immersion thermostat is set at. It will ignore any the ASHP says. Mine is set to max, so it heats to around 73 degs with enough excess solar.

Have you been specifically asked to provide one?

sorry life is way to short for that nonsense.

Depends. I pay 6p per kWh for gas and two rates for electricity 13p and 29p. Add to the gas cost and efficiency of 85% the actual cost is nearly 7p for heating. If running a heat pump at night I get a CoP of between 3 and 4 depending on outside temperature. So 13/3 is 4.3p and 13/4 is 3.25p. So for a heat pump run on cheap rate, electric is quite a bit cheaper. Running in expensive period a heat pump is about the same cost on a cold day a limited expense. On a standard tariff of 25p for a normal punter I would get an average SCoP of just over 4 to 5 so then it's cheaper at all times of the day, to heat via a heat pump. Add a battery and PV it gets way more complex, but overall cheaper again for electric heating via heat pump. So overall on a new build you are not correct.

Which direction is south? Dining area is just odd. I would just do kitchen and dining as a single room. From the look of the amount of glass you could rapidly cook in there when the sun's out. Where is the hot water cylinder going? Assume ASHP is planned where is that going. Or where is the boiler going? Concider stacking the washer and dryer on top of each other. Give your self some worktop space in utility. How are you doing ventilation, if MVHR or MEV you need to find a home for that also. Stair direction doesn't sit well, open front door and look straight up the stairs? Someone coming off the bottom stair could easily collide with the door being opened. Very little general storage space?

Eco4 sounds like you are trying to fudge the grant system, so you get the benefits needed to qualify but house is too good, removing a boiler to qualify so you no longer have gas could be seen as wrong, even if it broken. An assessor for the grant would only have to do search on property billing and they would know you had gas. So move on you don't qualify. All utility comparison websites know what tariff you are on and what meter you have, so I am sure it's a tick box on a grant scheme, for them to check. You could just get the £7500 grant for a new heat pump. It's only £7500 of tax payer money but.. but better than being caught out...

Are you German? Or just like using fancy words? So have to look then up.

I got the quotes and decided to be self insured. Contractors came under their own insurance or not at all. Insurance companies, it's money for old rope, never hear if anyone claiming. Are you are actually covered for anything in reality, never would expect them to pay out, if they did, it would years later after a battle.

It's a bit like an MOT for your car. Your mot is still valid, if broken down and behind a tow truck. Your EPC is still valid if you have a breakdown - instead of getting it fixed like for like, you are just replacing with a different heat technology and once installed you will get a new EPC based on that, as the base case. Don't do anything, just go through the process, don't even mention you have an issue with the boiler, it doesn't matter, it's going in the skip at the end of the day.

Which is not real if you set up the system correctly. I manage the floor temp at around 19. This means the heat pump supply flow goes down to around 11.8. neither are an issue. I have the same feelings for it also. Not a fan!

But completely different size to all standard plenum and terminal connections. I would stick to standard ventilation stuff for ventilation, rather than trying to bodge because you may save a few pennies.

So will the garage floor be insulated as well as the rest of the house? If not you will be unlikely to get a balance out of the heating and most of the heat in the garage will take the easiest route - which is down, not into the room. Make sure you really think this through.

Well really compressors, not pumps. But not true, Mol weight of gas will reduce, so should move to another point on the compressor curve, depending on mix ratios. But almost all boost compressors on the grid are gas turbine driven, changing the compressor rpm is also possible to compensate. But a compressor re wheel may be needed, but that's pretty basic in the grand scheme of things. The seals on the compressors are already equipped with dry gas seals, and have a zero emission recovery systems fitted. We already had three pressure stages in the distribution system, high, medium and low, generally low pressure goes into house. Bit black and white, likely to be a mix not straight to hydrogen.

I must be missing something - UFH in garage?

Never assume anything. MVHR is ventilation there is very little heat movement going on. The flow rates at about 0.5 air changes per hour so not a lot air movement going on either. The ground floor heat is carried via convection current upstairs. It will occur with or without any ventilation present. Warm air is less dense than cool air, so goes upwards like it not. I would have your UFH in the bathrooms AND an electric or dual fuel (water and electric) towel rad.

Why, when it's being made with excess renewable electricity that would otherwise be switched off? Not sure we have enough grid capacity to power every home, so not really an option. We need fuel mixes that have low CO2 output. If we are going N2 or gas/N2 mix for gas powered generators (we will have to do this for grid stability), then the same pipes are used to transport that gas then a mix going to residential is an end outcome.

Plus the Scottish government has arrangements in place to start selling it the the Netherlands. Several hydrogen plants are in construction or going through the planning phase, to make use of excess wind power. BG was back in 2020 was starting to replace gas lines suitable for nitrogen. Watch this space, I'm with @nodon this. It coming even if you don't want it.

Just seen the dates on this thread - dragged up from the past!

You can get the same outlet temperature with a water based coil. Doesn't really change the science of the flow rate being too low to be effective. Only really way to make MVHR cool is to have everything oversized for high flow rates. Configure setback to be normal rate, normal rate to be boost, then the normal boost setting to be a super boost just for cooling. Basically have the unit run full speed for cooling, still won't be that good.

UFH via a heat pump in cooling mode, is working quite well. Mostly if house gets too warm from solar gain, the period to get back to normal is shorter.

Have both, MVHR just reduces the ventilation heat loss, fabric heat loss is still there.

Gas connection means a daily standing charge. So if no gas appliances, your just giving money away. So up to you - around £100 standing charge for gas you aren't using or nothing to pay?

I like this design, but would replicate the cross bar in the window above the front door and the downstairs windows, but not the door side panels.