JohnMo

Good you've looked.

Big openings, hope you have done something to manage thermal gains from the sun. You may fry with low spring and autumn sun.

G98 is pre approved so you are only notify after installation and communicating. G99 needs to be approved prior in connection to grid. So depends what you want size wise.

We went through the pain of this on our build. We ultimately travelled 60 miles to the companies main show room, and nearly every window/door on show had a defect, either the handles or seals were not doing what they should etc. Ditched that company and uPVC all together. Moved on to better, but more expensive unfortunately, but as @Nickfromwales says, once installed they should be there a long time.

Advantage of the battery in the system is use case becomes simple. Took me a while for that realisation, keep it simple. Think the "normal" diverter and battery control may fight each other a little and you certainly get electric slipping past to the grid.

You really ignore internal wall U value - you have a a huge opening between rooms called a door, which could be either open or closed. Be carefull using AI for anything - would generally be my last port of call, never the first Rsi is the surface resistance of the internal face Typical internal surface resistance: Roof / Ceiling 0.1, Wall 0.12, Floor 0.14. Rso is the surface resistance of the external face. Typical external surface resistance: Roof / Ceiling 0.04, Wall 0.06, Floor 0.04.

Well that was all pretty simple Sonoff POWR3, £30 from Amazon An indication 20A switch for immersion heaters, a small JB and surface mount 1G box and 2 packs of glands £15 from Screwfix. So £45 all materials. 1 hour research on adding Sonoff to Home Assistant - Added Sonoff app to phone for pairing, same app added in Home Assistant plus SonoffLAN. Simple automation, trigger - PV generation above 500W, condition battery above 98%, run immersion for 10 mins, restart automation if condition remains true. Sends me a notification. Also records energy usage so added that to home screen. Wired in parallel, so switch can trigger the immersion manually. Indication light on switch comes on when relay is triggered.

A whole £2.50 per year. Think I will keep the TV.

It would be a noisy world when the temps to sub zero - what CoP do you get?

According to the text, starting in 2027 there would be a full ban on small (<12kW) monobloc heat pumps and air conditioning containing F-gases with a GWP of at least 150, with a complete phase-out in 2032. But that would be only new equipment and those needing to be regassed I assume. Not sure how industry would get on. But other than that R32 or R290 in decently designed system makes no difference. Same CoP, same running costs, R32 generally cheaper to buy, where R290 should be cheaper to produce as it runs at a lower pressure. Go figure why you have to pay so much fur an R290 unit.

Sounds like you have some expensive panel heaters disguised as a TV and amplifiers. Just check our TV it's been on for the last hour and it's almost cold to touch.

Have reread the above with interest. Have had a PV diverter, which failed. I think with batteries a normal PV diverter may not do the best job. As you say use the battery as buffer for the PV, run a 3kW immersion at 3kW rather than micro switching at low wattage. Just limit the run time but leave as something meaningful. I have added my ASHP as the first port of call to divert excess electricity. ASHP has a double set point, so use a Shelly relay to switch to a higher flow temp than normal WC to buffer heat into the floor. Will set the second threshold at a slightly higher battery SoC, to then divert to immersion. Basic kit for the immersion divert is a Sonoff POWR3, a manual switch to allow the Sonoff to be bypassed manually, total spend £45. If the smart relay fails it's £30 to replace. Diverter is silly money and not really needed with a battery. If you get paid for export, just export

Mine couldn't be more easy, its the default setting on the ASHP when doing WC. When compressor is off it just drops to 12L/min.

Looks nice - Why so well insulated when you have 3m or so door that gets opened? Or are you planning to heat it and not open the huge door? You also need to look at building regs for the ventilation required if it's anything like Scotland it's huge. Can't see from the drawing do you have a secondary door, so you can get in if you have issues with roller door?

I currently let my ASHP circulation pump run all the time, it takes heat from the house and via a fan coil keeps our summer house warm all year. Even taking 21/22 Deg floor temp it seems to keep the summer house above 18/19. Plus any solar gains get balanced out.

Adding battery isn't cheap. This time of year battery gets fully charged at night on E7. Have found the expected solar generation can be a bit hit or miss, we seem to have our own micro climate. Then depending on outside temp, heat pump can run in the evening. Last night (midnight) the battery was down to about 30%. The day before with very little solar was depleted by midnight. So my base case, now clocks have changed, by 0830 battery is fully charged. 0030 timer set to get battery fully recharged overnight. DHW cylinder gets heated at 0030 on E7 electric via heat pump to 50 deg, heat pump then does heating until 0730, can run on either of two settings, standard WC or and elevated WC (3 degs hotter) based on thermostat settings and actual house temperature. At 0730 heating is mostly off, but standard WC setting runs in background, but due the charging floor overnight, and a lower thermostat setting, is generally just circulating water. Then if excess solar being generated have automation to set heat pump to elevated WC, so heat pump runs and buffers heat to floor, but heat pump is likely to cycle. So really about making best use of excess solar. Heat pump running will mop up 800 to 900W, but could be generating in excess of 4kW.

That's something I am sure of. I want PV to charge the battery, I don't want to export. There are two options I will implement, first run heat pump at a higher flow temp and buffer heat into floor. The other is to put heat in hot water cylinder via immersion. The heat pump automation is between run rise and sun set, battery above 95% SoC and generating more than 1500W, run heat pump for one hour - this is repeating action. So if SoC stays above 95% and PV keeps generating more than 1500W the timer keeps getting reset. I may need to add another bit in there to make it seasonal. So looking to do similar for the immersion, but instead of matching export to immersion power, looking to put the full 3kW to the immersion. So it may be better setting the automation similar to the heat pump, but set SoC to above 99% and then power immersion for say 10 mins (500Wh) with a repeat action. How does that sound?

Things I figured out Monitor what happens just prior to a compressor cycle occuring. And when it stops. I then set my target flow temperature around this. So set a WC curve around this also. For my system if I don't have the circulation pump on all the time there is plenty of cycling. This is my ASHP at the moment. It's about 4 degs outside. The WC curve is set to coincide with a return temp at 22.7. At the moment I have a run time of just over a hour and an off time of 40 mins. Read and then read the manual many more times to understand what you can and can't do with settings. dT starts stop hysterisis all make a difference to run times and cycle times

Powered it's self off. I have just bought a Sonoff POWR3. So now just need to put automation(s) in home assistant. Something like PV output above 1500W and battery above 98%, run immersion. Need to put a cut off in there, so if battery charge drops below say 95% the immersion switches off - repeat

Opened up the box, and found the fuse blown. So first job replaced fuse and check over the wiring to the box. Other than that without desoldering it cannot be taken apart easily. Big heat sink and fan at the top

My second PV diverter has now given up. Coming to the conclusion the multiple switching isn't good for their health and they are cheap rubbish. Not willing to part anymore cash on them. So looking to go basic but smart enabled. Control scheme will be something like x kW being generated, battery state of charge is higher than x%, run full 3kW into immersion for 30 min recheck and run again etc Can do the control via Shelly and home assistant - have both already. But need a relay that is happy switching 3kW reliably - anyone got a recommendation? Not sure I would trust a Shelly do that directly Does the control sound feasibly?

Think the important bit is to drop down, that kills any thermal gradient which leach away heat from the cylinder. If it's pipes at the bottom of the cylinder I wouldn't bother, as that area takes in cold water when you open the tap so is cold quite quickly anyway.

Can't you just change the max flow temp setting down from the default 82 to something lower. Condensing mode stops when return temp exceeds about 54 degs, it has no care what the flow temperature is, so if you are getting a 10 Deg dT across your coil you could just the max flow temp to 64, have condensing, good efficiency all year. So now your boiler runs WC in heating mode, and up to a max defined flow temp (by you) in cylinder heating mode.

Why do you need to flip setting between summer and winter? You should be able to define an outside temperature (if doing WC) your boiler stops doing heating, then it just does DHW. When you are doing PDHW, you are really operating your boiler more akin to a combi boiler, your diverter valve is outside the casing instead of inside. The heat exchanger is a cylinder instead of plate pack exchanger inside the boiling casing. So the heating is just treated differently to CH and different heating parameters. But you can do each independent of the other. So nothing to change between sumner and winter.