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I came across this chap, could be useful for anybody building double block with a block beam floor. I think his videos are pretty good at explaining the building method. https://www.youtube.com/channel/UCwws-NyIJiRlqVy_X3yugfA

They are very sensitive switches and I would suggest you look carefully and find one with a low flow rate of 2+ l/m.

Do you mean it has an auxiliary tapping 2/3 of the way up on one side ( which is a hot return tapping ) ? A regular cylinder has cold in, side mounted at the very bottom x1, combined hot and vent out of the very top x1, and nowt else other than the coil tapping's which are hydraulically separate.

My view is that if you don't have mains gas, and really need high temperature DHW, then the best option may well be a Daikin hybrid ASHP/LPG combi. They have a good reputation for reliability, and use only a modest amount of LPG, as they use the ASHP to preheat to round 45 deg C or so, then boost this up to 55 to 65 deg C with the small LPG combi. I'm not convinced that any of the CO2 ASHPs are a mature enough product to invest in yet.

#1 - find an engineer qualified and with the right kit to service your CO2 ASHP. #2 - ask how much they charge #3 - buy standard ASHP... Not trying to knock this but my experience of owning and living with a Sanyo CO2 unit was painful as the kit is specialized to the point of if you connect a standard pressure tester to a CO2 unit you’ll be picking the bits up a hundred yards away... They are a niche market for high temperature ASHP and have never really caught on. Go with standard, plan accordingly and boost using off peak E7 and then spend the rest on a nice kitchen.

Not very private, it was on here lol. ?. @PeterW had me drive 7 hours in a round trip from Edinburgh to Preston to collect one! That’s the one I got from there anyway!

No practice needed just fit them it’s easy all you need is to follow a couple of rules. Get a towel and sit it on the floor beside you this will ensure you keep all the plastic bits out of the crud, keep everything grit free, clean everything spotless, the rubber o rings hate grit. Cut pipe clean and square remember to install a pipe stiffener, in every end of pipe. Mark pipe with a pen at insertion depth to ensure correct insertion lubricate O ring, lubricate pipe end Remember to put locking collar, nut on before installing fitting. Try to use a plasson spanner I have found these far superior to adjustable grips If you haven’t got the correct spanner just get on with it it’s not the end of the world, just don’t over tighten.

Reading this thread is only serving to show that a gas boiler is not the best mate for under floor heating. I know conventional wisdom says if you have mains gas, use it as it is the cheapest form of heat. For low temperature under floor heating, an ASHP makes a much better companion. My own system is about as keep it simple as you can get. the ASHP drives the UFH directly, no buffer, and a small 5KW ASHP will happily supply water at 37 degrees and modulate down to very low levels to maintain that, and running at low temperatures like that gives good efficiency from a heat pump. I still think there is merit in individual room thermostats. We only have 3 heating zones, the big kitchen / diner space, the living room and (not yet fitted) the utility room. All loops are fed from the same temperature water from the same manifold and pretty much the same flow rates to each loop, but the kitchen / diner is the last room to reach temperature and shut off. That is simply because so much of that room does not have UFH e.g not under kitchen units or the island, not under the stove, and not under the corner of the room that will eventually be the pantry. So probably 1/4 of that room does not have heating pipes under it, so it is now wonder it takes a little longer than the other room to heat up. I have used the dry biscuit mix screed as the heat spreader medium under our wooden floors downstairs and am very happy with it. Upstairs, just in the bathrooms I have UFH with spreader plates and this does not seem as effective to me, but then again the heat has to get through the wooden floor, the wet room tanking membrane then the tiles so it is probably no wonder we get less effective heating there. Lastly with the level of insulation you will have, you WILL need separate control for the bedrooms, much of the time they won't need any heat at all, we don't have bedroom heating, but you can achieve that by just valving off the upstairs manifold as a single zone if you don't want individual room control.

Yes, noted, but you don't have a mix of emitters over a number of floors. To have one flow temp to all the manifolds with them just having pumps is not a good idea, IMO, given I've done such installs and found it essential to be able to choose a slightly higher flow rate for the UFH over the timber floors, even with aluminium spreader plates. Bear in mind the UFH here is router'd into insulation with no aluminium plates to conduct and dissipate the heat effectively.

I played around with several ways of controlling the temperature of our house, and settled on a pretty simple system, with a +/- 0.1 deg C hysteresis thermostat that turns the heat pump on and opens the UFH. The UFH pump runs all day, whenever the timer turns the system on, and does work to even out the temperature in the slab well. I personally don't see the need for anything more complex than this, as it seems to control the house temperature very well.

IBCs for rainwater has been done before on here - think it is @Bitpipe who did it. And I’m all for value engineering ...!! I did an MVHR from electrical duct and pipe fittings.

I would have put money on you before you even started yours @ProDave Sorry @Onoff But for the avoidance of doubt we don’t need photo evidence from either of you

CPC sell them and if you ask @newhome nicely, she will probably drive 7 hours to get you the right one..... ?