JohnMo

That is pretty much what RED do, they use a Harlequin cylinder, 1.2m2 heating coil and a big DHW coil, the cylinder is vented, the water in the cylinder just stays there to carry heat like a thermal store

I enjoyed thermodynamics at HNC level and at degree level until the exam. Completely messed up the exam at degree level. So was dropped after that.

Thanks @sharpener for questions prompting me to think about different things and ask the right questions.

Just spoke with the electrician and if I want the whole house in a power outage it would have to be via a manual change over switch. Which isn't really what I wanted. So we are now going Givenergy all-in-one with gateway. The only limitation is inverter doesn't like generators, so once battery depleted and I start the generator the grid / generator change over switch will disconnect the battery/inverter as well as the grid. He said I need an additional earth spike. More money, but bigger battery, less faff.

From what I can tell you wire so it will give the 5kW output in an outage or you can use dedicated EPS function, for a few circuits. But have just sent an email asking the question

Our dishwasher takes hot water, but it only really works if the dishwasher goes on as soon as you have finished using the hot tap. Otherwise the water draw is too small to get hot water in to the dishwasher. 50% compared to what and when

If you only intend to have 100mm insulation in total, I would keep my money in my pocket, by not doing UFH. The downward heat loss will empty your pockets for ever more. Your heat loss downwards is based on UFH flow temp and the ground temp. So say 36 deg flow temp and 6 deg ground temp., So you have a delta of 30 deg. If you had radiators the room temp and ground is used to find the delta T, so 21 - 6 is 15. Heat loss is based on the floor U value multiplied area, multiplied by delta T. So everything else being equal, the downwards heat loss is double with UFH compared to radiators, because the delta T is double with UFH compared to radiators.

I still think your choice of heat pump is overkill. Looking at your SAP and compared to mine. Your Jan heat loss is 2388W, mine with the same average temp is 2979W. But at -9 Outside, our heating system draws 3.5kW - This being measured by a certified heat meter and tying in exactly with gas consumption (gas boiler at that time). When the heat season starts and most of the winter you are pulling just under to just over 1kW. Extreme days are not the norm. If you look at your graph and extent the lines left to the 1 to 3kW area things start to look very different. Both the Samsung and Midea are falling in efficiency.

Manifold looks like this, main stop cock at lower right corner, to the left is the pipe and isolator outside tap, bigger white pipe takes water up to plant room

I kept it simple just 15mm everywhere. Image of shower room, no bath in this room. Hot water pipes come from cieling cold out of floor. Two curved vertical pipes are to shower.

It all becomes very simple, no hidden joints, single run between manifold and each location. Once in the room I split down with tees to bath, shower, sink and toilet. Smaller than 22mm which the plumber may use as a header, big enough to supply the bath with good etc. Basically a secondary pipe in the hot water system. A pump, timer and thermostat, takes hot water from cylinder and pushes it around the domestic hot water system, so the pipe and water is hot prior to the water coming out of the tap. Our furthest tap is 18m from the cylinder, we have the pump on in the morning and evening, within a second or so, warm water comes out of the tap. Costs almost nothing to run so long as it's only running when you need it on.

6. A robot that cleans our gutters every six months would good. But I could always just pay someone for that, or do it myself as I do now

Would agree, also smart i.e. internet connected thermostats, hot water cylinder, why bother. Support or technology likely to leave the item behind, (not supported or operable) long before it breaks.

A2W also unserviceable, if they break.

https://www.gbnews.com/news/british-gas-hive-security-system-discontinued What gets pulled next. It's smart until the seller or manufacturer pulls the plug.

Or possibly the "real world" this is the real solution to the mass roll out of heat pumps. Easy to install, not expensive, no piss poor CoP to worry about. Competitive price wise with a normal boiler. Issue is general public perception, they think Aircon, expensive to run and cooling only.

Do it the same way as a Willis heater is plumbed into a cylinder. Tee into the bottom feed pipe and top outlet pipe. Small pump at bottom of cylinder pushing through PHE, heat pump on the other side in counter flow configuration. Edit reread the post ignore doesn't answer question

Same aims. If you have a 120l cylinder that's normally heated to 70 to allow hot water for the family, heating it to 50ish will not keep the family in water without a couple of heats. The other options are bigger cylinder, or to heat it to 70 by another means. That could be immersion, or could be a hybrid of HP and finish with immersion. We want it all to happen ASAP and manufacturers and installers won't connect to the old cylinder, so option A) is a non starter. And so is the hybrid option for the same reason. New cylinder is a big cost adder to upfront costs.

If they don't actually have it would say yes, but are you sure it doesn't have WC - last year it did and the CoP at different temperatures was the same, when I looked. SCoP can vary according to the country that generated the data you look at, as the baseline temps can be different etc. This thread would indicate the smaller one has a heating curve, not sure why the middle size one wouldn't

In complete agreement.

Not everyone will be able to afford your Vaillant heat pump. What do they do, be told sorry you can have DHW until you pay the premium, so no heat pump for you. The alternative could be heat pump for heating, a good solid basic one, and decent time of use tariff and immersion in the original cylinder. I mentioned the Willis heater, because its design basis to heat only the water you need. You can heat a small section of the cylinder only without multiple immersion heaters Do want this to happen sometime soon or in 10 years time?

Just negatives, simple solution is a decent tariff that doesn't inflate day time prices

My reply was to the above. A few steps to make heat pumps viable to the masses without ripping out functional DHW systems. Immersions may not the best or only solution. Time of use tariffs, come in many formats. E7 is one, and they don't have to be and could be mandated so they are not inflated prices during the day. Octopus flux export, gives you standard rated in the day and discounts at night it also pays well for exports. Plenty of criticism, no practical solutions voiced, or did miss them? While I was ducking!

So you are saying millions are wrong using E7. People on here still use it and are quite happy. You can't get an installer or manufacturer to agree with you. So chat all you like, nothing is going to change. Your goal isn't going to get realised without a pragmatic approach to allow everyone an alternative approach to a new cylinder.

Seems from this thread and others, some aren't happy removing their cylinder, so the option is limited, 0.7m2 and and heat pump, equals lukewarm water. Even E7 will give you a price equal to a CoP of 2 and was ok for millions for many decades. Do don't see issue. So what's your better solution if you don't want a heat pump cylinder.