JohnMo

Juton Demideck, expensive, no primers needed, unless coating steel, is just good and lasts well.

But why, bigger MVHR unit, 4x the heat loss by ventilation and maybe more noise and drafts. Just keep it simple. Floor or radiators single zone - done

Just do UFH throughout in a thick screed, then you have 20 to 30T of concrete to buffer against and batch charge the floor for a few hours a day. Big heat pumps also usually have a good turndown ratio. Only thing to watch is you have enough flow rate, so add a 2 port buffer and secondary pump as per drawing.

They do. I suppose they think, at say 3pm, batteries are full, PV generation doing 3.68kW, you then go into dump mode to the grid from the battery. To get paid for the total exports. Daft but some may do it.

Just use a smaller set back or none at all. The heat input is just about the same set back or not. You demonstrate well, that the heating system is just playing catch up for the rest of the day, so burning the energy.

Many will get as much pipe in the floor as possible to get the lowest flow temperature. But there are practicalities not covered by that sort of statement. Your heat source will have a minimum flow temp, normally about 25. It will also have a restart delta, in my case the ASHP will not restart after a heat cycle, until it sees a delta of between 6 and 8 between target flow temp and return water temp. Now once your actually heating your floor it will settle at 2 to 3 degs hotter than the room. So a return temp is going to be in the 22 to 23 range (once floor is warm it stays warm for many hours). So realistically your min flow temp is about 28/29, so WC curve or set flow temp starts there. So design the floor loops for about 30 to 32 at the highest demand point (coldest design day). Some comments on the pipe layouts I would move pipe away from external walls, have them a good 200mm or more away. The heat flux will heat the floor in this areas, but the edges will be coolest, so least side way heat losses. You never walk on those areas or there is furniture over so no issues. It's a waste of energy heating under kitchen units. Your whole floor area is a radiator all exposed areas of that floor will heat the room space. Having hotter bits really makes no difference. Halls are a movement space, yours looks like it will be the hottest space in the house. I have no dedicated loops in the hall at all, just use the pipes that transit through that space spread at 300+mm centres, it always warm because every heated room feeds it it with heat.

I lost the will to live using the heatpunk tool, (tried a few times) way easier and accurate is the spreadsheet on here

That's a lot of pipe! I've only 7 loops in 195m2 and one of those is only 40m long. Still only have to flow 35 degs to batch charge.

If you are still thinking solar, why not pre prepare for that with a PV diverter that does two immersion heaters, with a timer and WiFi if you need it. It doesn't care if you actually have PV or not, its just a CT clamp doing the the reverse detection.

See zero point have the floor heated below kitchen units. What's the long skinny room with red pipe at 100mm centres? You seem to have set the W/m2 the same throughout but I would assume some areas will have a different target temperature so a lower or higher output would be needed? What did you set your target flow temperature as? Are you zoning or running as a single zone?

First hit companies house h dissolved in March 24.

I would really challenge that, because it sounds nonsense. Put internal blinds in that are closed at the worst time, that's 60% of the gain gone. I managed to keep our sitting room cool enough with blinds, a 6kW heat pump via UFH, with cross ventilation and have about 36m2+ of glazing in that room alone.

Quite a small building will suffer massive overheating if your not careful. Ours with 70mm wooden walls with 140mm frametherm mineral wood inside and about 200mm in the roof got to 27 yesterday afternoon. A sip would heat up quicker. You need a high decrement decay buildup, hence not liking sip or PIR. Floor PIR is fine.

Maybe a Shelly relay as linked above, but use that to switch a suitably rated relay. Set up a schedule and have a manual override switch. The shelly is then just doing the low energy side of things.

The manufacturer has chosen a stated nominal capacity of 6kW, but at that OAT and flow temp it could output up to 8.9kW and down to 3.1kW, another manufacturer may say it's rated at 9kW and can turn down to 3.1kW. at -10 or -20 it may only output the nominal 6kW. SCoP is seasonal performance, so over all temperatures seen in the heating season - CoP is at a given OAT temperature. Divide 8.9 by 2.1 to get the CoP so 4.2 at 7 OAT and 35 deg flow temp.

Defrost just needs water. The 4 way valve reverses, the circulation pump continues running. The ASHP is now running in cooling mode, taking heat from the circulation water to defrost the condenser. As soon as you add hydraulic separation 4 port buffer or low loss header, the primary volume is heat pump and buffer - heating system is now excluded from defrost activities. Two things the system needs to meet, volume flow, and min engaged volume. Best way to have the system configured is one or two big zones using the ASHP circulation pump. You need each zone to meet min volume and allow enough circulation flow. If you meet min flow required but not the volume bit add a volumiser. If you cannot meet either min requirements, then configure a two or three port buffer with hydraulic separation. Only the water that needs to go to the buffer flows there all other water bypasses it. But doing that your control system needs to control charge temp on the buffer as well as the room stats. Don't install a 4 port buffer as these just add inefficiency. Unless you pay lots for a well constructed unit - bit like hens teeth.

Could you just add a check valve so it cannot reverse flow?

How long is a piece of string, maybe late September or early October to start or end of April, depends on the weather really and how your house is affected by it.

Modern building methods are no better, could be worse than old ones. The normal builder not giving a bit of care or understanding of airtightness. If you have no airtightness strategy you will have a leaky house. Window installation is a good example, mine were installed and all gaps filled with airtight foam, most installers will fit a trim over the gaps, leave the gaps unfilled to leak air and a cold bridge for mould for form. All holes through the building were drilled a duct installed and sealed in place. Once cables etc were in the foam filled and sealed at both ends. A normal builder would make walk away never to return.

Just think you are not really understanding what PV does or doesn't do. This time yesterday I was generating 3kW, today because its cloudy 600W. Relying on PV to do anything predicable is rose tinted glasses and headphones on mode. It does what it does when the weather allows. Your heating is generally running max load when the sun isn't out, when the sun is out you get solar gain in the house etc. During the winter this year lots of rain and many days with next to no generating from PV. But boxing day was sunny and we did the whole lunch powered by solar. Averaged over a whole it will generate xkW, next week is anyone's guess

Overall I would say there seems to way to much (over) thinking goes in to shed on this site. As above Our last (house) shed was sat on 6 old slabs on soil. It was still there 10 years later a good as new. A shed existed on site when we bought that house, it had been there about 20 years, was still there being used 10 years later - On slabs on soil. You don't need a concrete or mot base. Anyone saying you do is after your money. It's a shed. My latest shed is on a load of concrete blocks I had left over from the build.

I noticed my cylinder heating occurs about 10 to 20 mins after say a shower. So suspect cylinder is all stratified, prior to opening hot tap, cold water comes in at bottom and mixes with water at bottom of cylinder all the time you use water, thermocline rises etc. then it needs time to stratify again and then thermostat says time to heat.

I've always looked at it this way. Uninsulated pipes lead to heat losses mostly where you don't want them, heating and area unnecessarily. A buffer or volumiser in your case is a little like filling a kettle, put a cups worth of water in it, heats in about a minute, you have a an empty kettle after your cup of tea - no energy left. You fill the kettle it takes 4 mins to heat up. You take your cup out and there is still a lot of hot water left, the wife comes in she makes a tea etc. So for a boiler, the single cup situation occurs when the system doesn't have enough volume. Boiler starts heats, stops quickly as up to temperature really quickly, the water volume is low so heat is lost quickly, boiler tries to start (may have 10 mins lock out), starts, stops soon after, lock out etc. The full kettle situation, boiler starts heats the full volume of water. The contents of the buffer/volumiser get distributed around the heat system by the boiler pump, until the return temperature is low enough to enable the boiler to start. So now it's heating starts, runs for a longer period (more water to heat), stops, has a break (uses the energy in the volumiser to heat the house), starts runs stops, takes a break. Having the correct minimum volume keeps things running in a controlled manner. Same is true for all heat sources.

Doesn't mixergy plan heating cycles around your normal life style, monitoring what you when and circling with hot water?

Strap bands here also no issues 2 years in. Seems to be more of this happening, seems like money down the drain now and forever more to me. All the normal ventilation plus a load more by the MVHR, the additional 24/7 running cost plus an additional (small) heating cost due to the unrecovered heat loss. Going this way, get a humidity sensor or two, Shelly H&T are good. Then set the flow rates (keep them balanced) so the house sits at 45 to 50% humidity. Set to auto boost at 60% humidity.