dpmiller

The iboost monitors both outputs- it heats on no1 until that heater's stat is satisfied (or any series switch or relay you may have switches open) then it heats no2, but "tries" No1 every 15mins (IIRC) to see if it's requesting heat again. I've set mine -a thermal store- to master on the upper to heat to DHW levels quickly, but then the switch over to the bottom element to fill the rest of the tank.

but 4-strokers are ok?

I'd suggest there's something dodgy on the earth side of the pole transformer which could then allow local ground (and your neutral in the house) to rise towards the potential of the overhead line because of leakage through the bird? edit: which if any of the trips in the house had gone?

the UFH pump only circulates in the loops, when the TMV is closed the UFH is pretty much isolated from the ASHP circuit.

preplumb seems mostly to be Tectite or crimp fittings which can be a bit neater for sure but as above, unless the base cylinder is configured with ports in the right places and the external stuff oriented right, all the pipes can be in the wrong places.

Is the cold water tankfed too or is it at a different pressure to the hot? Might be the valve is a little unbalanced at the lower temp...

We were advised against black because it would have more of an issue with fading. RAL7016 as a foil on UPVC, it's a mid grey now, and if it fades it'll still be a mid-grey, lol.

Send your spec to World Heat (whcylinders) and see what they come back with. Happy to do bespoke and deal direct.

so make it unlockable then. Our UPVC windows came with a bag of little plastic clip-in bungs, to render the keyhole on the handle of fire-escape windows unuseable.

how much is the MCS cert worth to you?

RTU

that screed quote is well over twice ours...

have you the 50mm to spare?

strip of self-adhesive foam rubber? Bed and damp the slates in one.

how close is it to the plant room? could you (say) loop the return from the hot tank to the boiler through the room?

Did ours ourselves (clay tiles). Felted and battened by the TF crew but we did the rest and saved a fortune in the process. But would I do it again? not so sure...

@Declan52 is there any way of getting that clean blueish-grey that the local wetdash tends to be, in a rubbed up coat?

generally the gubbins of the unit bayonets into a bottom mounting boss so possibly no need to remove the cistern.

why do concept, developed design, and technical design all look the same to me?

to go through the timber frame on ours I used these: https://www.schiedel.com/uk/products/additional-ranges/ignis-protect/

Now it's not much more than an anecdote but... there's been s few sunny days this week. Reported diversion is about 10kWh per day (yes, I'm running hot water off every evening to pull some energy out of the TS) bringing the store back up to 88c and both stats satisfied. I've been able to do some monitoring of the DHW coil performance in the process and can see that the deltaT between store and flow out of the coil is around 10c at 10l/min sustained, less at single-tap flow rates. Plus the coil's volume means it's even better than that for a quick handwash. Oh as 20secs for hot to the ensuite which is about the longest run in the house. But what I find more interesting is this. I've been having difficulty believing in the heat loss calcs for the house, it's hard to wrap yer head round such a big house only taking a few kW to heat it. So while I'm surprised, I'm also pleased to see that since commissioning the TS evening temperatures in the house have dropped between 2 and 4c from a stifling 22-24c to a rock steady 19-20c. And all because the silly wee 800w halogen heater that I'd connected to the diverter isn't trundling away all day...

or you could go poured and down to 50mm

iBoost is more configurable and can drive two loads, plus has the option of the Buddy remote display

would the steel bend up a touch?

There are plenty of blokes in the local papers that do extensions and stuff. I'm gonna say try running your design past the chap that did ours from scratch as he's... good. PM on the way