JohnMo

Been thinking some more. Run the boiler and heat pump on the same WC curve. Can easily flick between the two heat sources, via a time switch. Or if the heat pump is smaller than needed, the return temp would and dT would not allow the flow temp to reach it's target, so then the boiler should take over if enabled.

This took about 10 seconds to find https://coolenergyshop.com/collections/air-source-heat-pumps/products/proinverter-air-source-heat-pump-6kw

You can do this, but I would not. I would do a normal UVC and external ASHP like @ProDave mentioned. I paid £800 (incl VAT) for my 210L HP cylinder. Plus £1300 for a 6kW heat pump. Does all the house, summer house and DHW. Cylinder came with diverter valve, one direction to cylinder other straight into UFH manifold. You are going to be getting through way more water than you seem to calculate. Very much doubt it would be that cheap for 6 adults even at £0.08 per kWh We use around 6kWh for 2 of us, so you could be around 18kWh with 6 adults

Can do if you design correctly. But more to the point, store so you don't need to blend down. Install a bigger cylinder? But just install a heat pump, you will be paying a fortune just for DHW. Secondary return heats the manifold also. You take the secondary loop to the furthest wet room, I then flows back to cylinder via manifold. Manifold is hot all user get hot water quicker, even you hot water appliances. Without it the hot water appliances will just be getting Luke warm water at best.

Your UVC has a valve that reduces mains water to 3 bar as well as doing other things. It also provides a balanced cold water flow outlet, so mixing taps function correctly. If you take water before this and use on a mixing tap, you may not get any hot water flow, depending on pressure before the cylinder.

And defrost makes a big dent energy output per kWh input. One degree change in outside temp can be the difference between CoP of 5 and 3 due to defrosting.

It does, so does the controller any thing in the system relating to heat pump. Each electric item should be metered. We take a big dent in SCoP because batch charge. The main circulation pump runs 24/7, as I use it to borrow heat from house to keep a summer house warmish. CoP of 5 doing heating and daily CoP about 3.0. but heated mostly via cheap electric. Our heat pump has only one pump, and a diverter, diverter is powered only when doing DHW.

Why bother and have a bucket load of wasted heat with heat loss, will be ok in winter but overheating house in summer. That makes no sense, so get in morning to wash and brush teeth and run the shower for no reason? Are you sure about that. Even if they do the slightest of cold they receive first is what will be heated by the machine. My general comments are UVC at 300L and store at around 50 degrees, heat twice if you need to. Always install a heat pump cylinder with a 3m² plus coil. Fast recovery main reason. Future proofing if you are not installing a heat pump now. Don't bother with thermal store unless oil heating. Thermal battery don't bother, cost to purchase daft. Cold water manifold that also, good for easy isolation. All tap water is taken from the combined valve on the UVC no where else. I would install a secondary return loop on the furthest room, the have a timer thermostat pump, or link a simple smart plug to Alexa and tell it to start pump when you want. I would simplify the manifold to one port and pie run to each wet room and branch in the wet room. Do the long runs in 15mm. What the heck is a power pipe?

Sorry this is just a load of waffle, stop trying so hard to save a few pence a day. To do what you want with a 6kW heat pump is a non starter. Flows sub 25 are a waste of time planning for because ashp don't go that low, min flow temperature is generally 25. I will not be responding again to this thread as it's just making hard work of a simple problem. But my thoughts are. 3kW max heat required, install 6 to 8kW heat pump. Thick screed floor to buffer heat, charge floor with heat on a cheap tariff over night, charge batteries on same tariff. If required run ASHP on battery in evening. Ideally if you had around 25kW of battery you would never run out of cheap electric. Problems you will have is defrosting of ASHP at 3-4 Deg and below, limiting power input. Different temps in different room, you embed more or less pipe.

I use these for my DHW switching. ASHP remote from cylinder. Not internet connected. https://www.rfsolutions.co.uk/remote-control-systems/mainslink-the-5km-original-switched-live-cable-replacement-solution/

So if you have normally zoned to death, set way to high. Octopus heat loss calculation will most likely over egg the cake anyway. So possibly a mile out on curve. Not quite followed that do you have a link?

Reduce the overall temperature, steady heating allows cooler house temp, while still being comfortable. Normally able to set temperature a good couple of degrees cooler. If your curve is correct radiator valves if installed shou6dtay fully open. Anything else means flow temp is set too high.

Various way to do it. My Atag combi is configured like this. Switching WC on and off no plumbing needed Cannot run Opentherm, cannot run on off control via simple thermostat (can but a few fudges needed and has to think it's in WC mode). If you are already running WC you could try this by disconnecting the WC outside sensor to see what the boiler actually does. Set boiler to weather compensation mode and max flow temp set to 60 to 70 degs. So cylinder heating control. Cylinder thermostat controls diverter valve kor 2x 2 ports) and a relay. The relay has the WC sensor wires going though it. When you power the relay the Weather Sensor is circuit is broken. Boiler now thinks it's no longer WC compensation mode, so ramps to 60 degs (could anything you set it too). Once DHW cycle is complete, relay makes WC sensor circuit and boiler goes back to WC mode. Convert to 4 port boiler. Plumbing needed Another way, is use the DHW circuit that is there. Add a pump, expansion vessel filter, relief valve etc. make a loop direct to cylinder coil. DHW call for heat, starts pump. Boiler assumes tap is open and sets to DHW temp. This maybe the easier route?

That sounds very well controlled. You have your cold spell starting today if the weather forecast is correct. We have a 10 deg drop from midnight last night to midnight tonight

All sounds good. I found very similar at low flow temp WC (on warmer days) was really high consumption due to cycling. Actually found running slightly higher temps and bouncing of a thermostat was better, from a consumption perspective. Through experimenting found at 36 and below, boiler would cycle on off every 6 mins (or worse), but at 39-40 would run non stop for many hours if I wanted it too. First 20 mins would result in responsible consumption, but let it run way longer and the consumption drops really well. So nice long runs win for me, but I can charge my floor as a good buffer. So you may be better finding the magic flow temp for very long running and use the thermostat to stop the boiler, so you don't overshoot room temp. I replaced my outside sensor with a fixed resistor, boiler thinks it 15 degs outside all year round. So runs in WC mode. Thermostat used to drop boiler in and out of set back mode

I have a mix of armaflex but you need to shop about as prices vary hugely and lots of Climaflex. If it's exposed where a mouse will get, wrap in aluminium tape. If it's exposed to low temps do 25mm wall thickness, minimum 19mm.

So you need an oversized HP first. Needs to generate the heat demand for 24 hrs in maybe 14 hrs to have leeway. Sunny day or not sunny days. Storage of energy floor is cheap it's also at a low temperature. Once house internal temp and floor temp match, zero heat is out into house. I would try to find a single thermostat that you can link to a price cap API. Or already had it built in. You place the thermostat in an average temp area say hall. Ideally you want thick screed, and a 0.1 hysterisis thermostat. In cheap periods you up the thermostat demand temp say to 21, and more expensive times at 20.5 and super expensive set to 16. No need to manage return temps, just keep it simple and understandable. I would also assign an elevated temperature WC curve to heat pump running, this has two advantages less likely to overheat house, when running you get a slightly better CoP. If your not very well insulated you plan wouldn't work full stop. I found a well insulated you don't need anywhere near those temps. Comfort levels vary in the 0.1 degs scale. We find 20 is fine in the day, upto 20.2, then it's getting too warm. In the evening 20.5 to 21 is comfortable any hotter is just too hot. If you have a battery and smart meter, just get a simple time based tariff. Something like Cosy gives 3 cheap time periods, run house and HP on that. Simple very little cost difference and your wife/husband will not divorce you, when they have been cold all winter, because you wanted to save 50p a day on heating.

What are you asking? You have lost me. You seem to be trying hard to do something, but no idea what?

And at the time they trained 100s of thousands of installer about condensing boiles - must have been in one ear out the other. Legislation is the only way things change. But the defaulte settings on most boilers is a flow temp of 70 or 75, which is the manufacturers also playing dumb.

I hammered my earth spike for the battery (in sand) got to about 20m deep before it passed the test.

Screen shot, shows outside humidity, house humidity with MVHR and summer house (pod) with dMEV. The days below were above freezing. This shot it was colder, with days well below zero, so house and pod humidity drop. dMEV has no different humidity than MVHR, within a couple of percent. I would spend time/money resolving cold bridging. You want decent install, and decent frames. If you have argon filled double glazed with a good frame Uw should be about 1.2.

Are trickle vents open? Do you have door under cuts to allow cross ventilation? Have you checked you don't just have an open void around the window frame, causing a huge cold bridge? That is the normal cause of that issue, bodge window installation, not filled the gap with a good expanding foam, just some cheap filler pieces hiding a hole. You NEED to find the route cause. MVHR isn't the magic fix. If so what's the point of all the work and upheaval?

Must say looked good, but a lot of work, but all by hand - not a digger in sight.

When you take into consideration the cost difference between an unvented direct (immersion cylinder) and the heat pump on cylinder version to buy. So like for like materials. 210L UVC direct heated £500 Dimplex Edel £2400. Advantage is CoP of 3 compared to CoP of 1 for immersion. Daily cost is 1/3 for the heat pump cylinder. But you have a few years to make up the cost difference overall. Around 5 years to break even point cost wise based on buying and heating costs. Plus you have to route ducts in and out of house. An extra cost adder, 2x 160mm holes through wall plus duct. If using house warm air from house, this is likely to need to be replenished via the A2A for the heat pump cylinder. Other consideration Time to reheat is very long for HP cylinder, so check that out. As you mentioned noise? Service and parts, you are going to a glazed over look, from the plumber for HP cylinder.

Good point Then this could be an option https://www.ebay.co.uk/itm/185631610657?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=yawjptzcrle&sssrc=4429486&ssuid=8KgwDlAbTJS&var=&widget_ver=artemis&media=COPY