JohnMo

So are you just pulling water from a thermal store? More out of interest. As you say, keeping bedrooms at 19, is the heating system just ticking away, so not really a reaction time thing. Do you have UFH downstairs?

Some cycling is possibly more correct. Short cycling really refers to very short run times and short off times. If you are getting short cycling your system design is poor, no matter what size heat source company to heat needed. You size system volume to ensure you get 10 to 12 minutes of run time no matter what. Then you have controlled cycles, which yield a great cop as well. Our ASHP is huge compared to heat demand, 6kW output from plus 30 to minus 15 degs with a minimum output closer to 4kW. Heat demand closer to 3kW at -9. Will happily supply house with sub 1kW heat demand, with very controlled cycles, just using floor as a buffer.

Looking to heat DHW takes around 1 hour each time. So say doing 2x heats per day. So you have 22 hours to provide 24 hrs of heating. (2142*24)/22, adds a couple of hundred watts only. Small heat loads need some thinking about, because too small an ASHP, DHW can take an age to heat. You really cannot or have zones, even if you wanted. As heat pump would cycle to much. Your heat pump is going to be oversized, but you can live with that with a simple simple system.

Is this a new build - What's the needs or wishes for 100mm centres

£400+ bonkers. Why do you need that many loops are you building a hotel? Either why would you not just do 2x manifolds in a appropriate places in the house.

This may or may not make useful reading https://community.openenergymonitor.org/t/vaillant-arotherm-owners-thread/21891/30

As said above, by @SimonD. But my only comment is on volumiser, there are two camps, flow and return side of the system - I see both with issues, without correct placement of volumiser and that issue revolves around DHW. So placement of volumiser has to out of the flow path of any hot water directed towards or returning from DHW heating duty. So either downstream of 3 port diverter on central heating side or downstream of central heating, but upstream of tee where DHW returns to system. Reason I say all the above, if not followed you needlessly heat a volume of water while doing DHW heating AND that volume of water with be pumped in to you UFH system, which isn't good.

Isn't the correct way with EPDM to take a skirt up from horizontal to vertical and up and under any drip ring around roof light? All seams either heat welded or correctly bonded. Difficult to tell from images what they did. My roof is all mechanical fixed and heat welded seams. No mastic or glues. What the roofer is proposing is a bodge at best.

You generally calc at -3 for England and -5 for most of Scotland some bits down to lower. We generally never go above 6kW load for the whole house (our battery inverter size), 6kW ASHP, MVHR, borehole pump, two ovens, induction hobe, microwave , kettle, everything does does demand electricity at the same time. Our largest draw from the grid is battery charging and that rarely even at 6kW. So you can also charge two cars at the same time if you wanted.

What is your heat source? Why wouldn't you be running weather compensation no matter what the heat source - so on 24/7 ticking away? If gas assume you are going priority domestic hot water, not S or Y plan?

Think it's whatever your boiler installation manual says and or whatever the plastic pipe manufacturer says. Unless they say nothing. This what Hep2O says Just looked at my old boiler instructions and it makes no mention of special distances from the boiler for copper pipe with plastic pipe allowed. Original equipment manufacturer instructions will normally trump building regs

But isn't the point of you as the property owner checking documents and having them corrected, by your so called consultant? Maybe my engineering background and the obligatory nature of documents reviews and sign off, be it bythe contractor or by client, both have equal responsibility to get stuff done correctly. I never hung back with feedback for all design and as built documentation and made sure it represented what I had paid for or what had been built - not what someone thought they could fob me off with.

This what Samsung say about water volume

That number is defrost support only - not for cycling. Mine is a similar distance from house, it would be worth doing the actual calculations yourself to double check. I get around 1.2m³/h flow through the UFH, without additional pumps, longest loop is 110m. But having limited flow rate doesn't require a buffer in the system, you just add a fixed speed pump to the return piping and run at the lowest speed to achieve the flow you require (it's there to make up for a fixed amount head loss only).

I just use UFH in coop and heat mode, keeps house a more stable temp and cools quicker after getting solar gain. When house is hotter than outside we open windows and doors also. Bedroom window is most nights.

Possibly not, as the travel slot comes to an abrupt end with door just over 90 degs. That abrupt end breaks all the plastic bits inside and bends the metal parts as door slams open. Very poorly thought out design. Should really have a hydraulic ram to slow door down (similar to that linked by @Beau), then self latch.

I am down to about 300-400W (it fluctuates a bit), 2x MVHR units, heat pump always on, treatment plant, UV steriliser for borehole water treatment. Removed 75W by changing the settings on heat pump for the circulation pump, which by default is always on, to on when requested by heat pump internal controller.

Our doors have these, but, if someone opens door a bit and wanders off, and then the wind catches the door, the mechanism get ripped apart. Now have two doors with mechanisms that don't work because of this.

They look good. Just did an image search and they are listed on Amazon UK site also https://amzn.eu/d/6z1PyQy

A photo or drawing always helps. Way better than many words. But you need the EPDM to lap over the fascia boards so you don't get water entering the gap between the fascia boards and OSB. Assume this is what you are asking?

Wish my heat pump controller only used that much electricity. It pulls 17W and often bumps up to double that.

These are your friend https://amzn.eu/d/2A1Z9iM

So will you have to an additional circulation pump? Is 50L enough to stop short cycling if zone 2 is only running? A topic never really appreciated with low temperature UFH (assuming you are doing low temperature) is the nature of its self regulation. Especially when running weather compensation the floor surface temp in mild weather is 1 to 2 degs warmer that the room it heats. This small temperature difference means small fluctuations in room temperature, affect heat output from the floor. So as room gets close to floor temp heat output drops, as room gets colder floor output increases. This difference is sense by changes in return temp, to ASHP and it modulates output accordingly. So in effect you just don't need to zone. Your floor is your buffer, without buying stuff you don't need - buffer, additional circulation pumps, valves, thermostats, actuators, more antifreeze (if you use it) They are just towel dryers not room heater, your UFH is the room heater. So you have on for an hour or so after baths or showers, think mine have a 300W heating element in. If room is already warm the thermostat doesn't kick in. So running is not excessive. That's down to your ventilation strategy, more than your heat strategy. So maybe something to wrap your head around in another topic?

My front door is inward opening, all others (4x bedroom and french doors) are all outward opening. They get caught by the wind easily so be careful.

Read the grant BUS details, basically all DHW and Ch had to be supplied by the heat pump.