JohnMo

I wouldn't class any of that is landscaping really. That's all stuff you have to do and should be done prior to a building be classes as complete.

People with big houses and loads of showers, once you get the water supply issues sorted, you may need to start looking for a cleaner to keep all those bathrooms clean.

Simple fix a 2 port buffer of around 25 to 50 L capacity (closer to 50L is better), across the flow and return loop to the boiler or across the flow and return from the UFH, where ever is easiest to install. No need for low loss headers or 4 port buffers and additional pump (s). Parts list Two Tee pieces, A buffer or volumiser https://www.theplumbshop.co.uk/products/expansion-vessels-intermediate-buffer, these are cheap enough, you need to insulate yourself. Two isolation valves

Not definitive, but the choice of how ASHP circulation pump runs would be an installer selection option. So could be either or. But to add confusion some control schemes work by having a thermostat the buffer, the thermostat being a run permission for the heat pump, in this case the circulation pump would almost definitely be off, while the buffer is not calling for heat. Unless you know you are connecting everything up, having a buffer not having a buffer it's all very academic, and doesn't make a jot of difference

Every day a learning day. So had a dig round the internet to find a drawing of the layout in fig. 4 more applicable to a UK cylinder with a dedicated recirculation loop taping point. See below. The bypass and return valve would be a globe valve or similar to allow accurate and repeated flow control. This setup should allow a continuous flow of water through the cold port of the mixing valve

I also had a full landscape plan with loads of trees etc, no one even looked or cared at time of building sign off. Tick in the box stuff at the planning stage. Something to hang you by, if someone complains later I suppose

I know my heat pump has a couple of circulation pump modes, the default to run continually when there is a heat demand, but I don't have a buffer. The other mode is a sniffer mode, where the circulation pump runs for a couple of minutes then off.

Forgot to mention there are two sides if you have a 4 port buffer. The side I explained is the heat pump side or if no buffer. With a buffer, the heating side pump is controlled by room thermostats only. The two sides of the buffer work independently of each other.

Basics Heat pump will have a target flow temp and dT between flow and return. First the circulation pump starts, the heat pump reads the return temperature. If the return temp plus dT is below the set point, the ASHP will start adding heat. Heat is only added to maintain dT. Through the heat cycle the return temp will increase as the emitter and room temp dT closes. Once the supply temp exceeds set point by a predefined margin say 0.1 deg, the heating cycle stops. The circulation pump continues, and monitors return temp....

Get your manual out or download it. It will have explicit instructions on system volume and the required additional size if required. You will need to calculate the approximate system volume. If you are getting bid swings in pressure and your expansion vessel is sized ok, you may need to look at the pressure setting in the accumulator, it may need blowing up. UFH pipes will be approx 14mm bore.

Would think you need to know some basic info first, if you have water available. The static and dynamic pressure and flow rate available. Here is a snippet from a a Gledhill cylinder installer manual, let's you know about flow and pressure.

Don't try it on UFH as it sends the room temp in to slow yoyo of undershoot and overshoot. The algorithm cannot get its head around why room temp isn't changing as predicted. Exactly, this is especially true of UFH as the floor temperature may only be a degree or two higher than the room. So if floor temp is 22 and room temp 24, heat flow is either stopped or it is actually being removed from the room into the floor top surface. So there is no advantage having anything smart to compensate it does itself. Also if the room isn't taking the heat away (or less of it) from the radiator, the boiler sees a higher return temp and automatically modulates it's output downwards.

Possibly a good example of the difference of radiators and UFH. For our house that just didn't work (I did try), UFH is just way to slow to be putting different temperatures in to different areas and hoping it will keep up. So I either charge the whole lot with heat overnight and leave to give out heat through the day, or when very cold it just gets a longer charge, may even run most the day. Hence no need for zones or any controls other a 0.1 deg hysterisis thermostat timer, to control when the floor charging stops and starts again.

Interesting

Do you need to log in to get access to the installer menu? Mine, not Bosch, you need to enter the installer log in code, before any installer designated menu's come up.

Not sure why a mixing valve would not work at the top if a cylinder. It is supposed to be first thing hot water goes through. https://forum.buildhub.org.uk/topic/21490-thermostatic-basin-mixer-taps/ Are you sure the issue wasn't the plumber not installing the check valve on the secondary return. As then if the secondary return pump is off the easiest route for the hot to go would be to reverse flow through the secondary loop to the hot water outlet.

Is this any use, found it in a manual for my heat pump cylinder. Is 4 showers at the same time an every day event or once in a blue moon? As if a rare event you can always increase capacity by switching on the immersion and heating to a hotter temp. Just add a mixing valve to the UVC hot water outlet.

No, and no need really. Once I set the winter running regime, it will be left to do its own thing.

Well done you. But you do add complications, you possibly need or have a buffer In and out quite a lot, good thing about airtight houses, opening a single door doesn't cause a draft. I actually operate two WC regimes, shoulder months use floor as a storage heater, charge up at a higher temp for a out 6 to 7 hours instead of running all day with very little load. Then when it's really cold outside that run time extends across the day. But so the house is the right temp at bedtime, the heating is generally off about 6pm anyway. Still all done single zone. One thermostat/timer in the hall.

Mine is pretty much as your first post for wiring. I didn't select what circuits are used by the generator, just got a 7kW generator, so most things can be on. No point not having lights, TV and kettle.

G99 you can have any size system you like, the inverter is just set to match the allowable by DNO.

Even if your airtight test shows you have a leakage rate of that, that isn't the figure you would used in a heat loss calculation. The 50Pa used during the test is the equivalent of extremely high winds, on all sides of the house - so you have to have the lowest temp and extremely high winds from all directions at the same time, which is rare or impossible. You would be fine using 0.5. It's only really going to be that if you have mechanical ventilation running 24/7. Otherwise the infiltration would less than 0.2. If you have a SAP report the infiltration rate will be in there.

Don't you worry about a pipe freezing up while you are away? Not sure I have or ever would turn my heating off, in the heating season, even when I worked overseas, the heating stayed on low.

I used one of these, all metal construction works great https://www.amazon.co.uk/ESR-Generator-Changeover-Transfer-Enclosure/dp/B079Y3PJN8/ref=asc_df_B079Y3PJN8/?tag=googshopuk-21&linkCode=df0&hvadid=211160703339&hvpos=&hvnetw=g&hvrand=512328552230480576&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=20342&hvtargid=pla-427697215563&psc=1

90mm is no where near enough insulation for UFH. Should be at least 150mm more if you can.