PeterW

Yes you need pump valves either end. I would use Pegler ones. I also think this PHE and pump need to go across the tank input and output, not across the vent pipe and output. Reason being, the PHE and DHW need priority and tbh the tank won’t stratify as it’s too small - if you use the vent pipe, there is a chance that the PHE pump will just pull the tank content rather than take the full heat of the boiler which may result in lukewarm water.

Can’t beat these Wilo Pico pumps for performance - virtually silent too. Best price seems to be Screwfix too

You don't want to know what @Nickfromwales was doing .... ?? ?

Thanks @JSHarris - I was referring to the one that @Nelliekins linked as that was the one we had issues with. Useful to know that there is one with a decent current control.

You cannot wire the pump direct to the switch ..! Have to put a relay in as otherwise you will fry the contacts, irrespective of what the MIs say about current rating ..!

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

#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.

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

Ok - so you’ve got around 350 litres of water in that system, and would need an expansion vessel of ~40 litres to cope with the loops, but you could drop the pressure to 1 bar and it would be fine. If you are still planning on using that PHE setup then you’re going to need to be careful with the pump positions and also double check the boiler doesn’t have an internal pump also. Do you already have the flow switch ..?? BIG TIP - fit a non return valve before the switch and after you have tee’d off for any cold supplies - assume you’re also fitting a PRV..??

Irrelevant - just set a blending valve to 38c and leave it alone. Just one off the coil will be fine.

You could always stick a Sonoff TH in the circuit and use it to control the on/off by humidity. That plus the transformer is change of £20 all in

For the footings I’d just get a roll of 450 or 600 DPC and roll it out - can be reused. Blocks need stacking on pallets first then covered with a tarp - stops them getting clagged up.

The 8.2kw one is change of £800 - think we discussed them last year.

1200ga is normal for DPM. Cheaper as a bigger roll.

You’re basically turning your boiler and tank into the same sort of setup that you get on an oil boiler here - a stored water combi. Putting aside the issue of filling loops and venting for a minute, I’m trying to come up with any downsides to not even bothering with the UFH buffer as the DHW tank is working as that anyway. Is the UFH pipe 16mm PEX..?? And it’s 2.2km long ...??! How many manifolds and loops ..?

I think I / you need to draw this out as I’m still not sure where the connections are going. Can you get the KW rating for that coil ..? I am just concerned that even on full chat, that 30kw boiler won’t kick enough high grade heat into the tank for a pair of showers plus the UFH but could be wrong ... Edited to add : the answer is no on the recirc of heat to other floors as the three way would be stopping recirc other than of the manifold it was supporting.

Actually, basements are normally cheaper per square metre than any other part of a build as they also incorporate the foundations. If you compare the cost of a basement to adding the same as floor area to a normal property, including windows, walls, floors, roof etc, then it’s surprisingly low.

Ok so that will never happen until the air temperature and fabric temperature all equalize and given you have continuous losses through both MVHR and fabric you will be chasing rainbows ... The “simple” approach would be to run a pump and zone valve on each manifold with a bypass across the flow and return inside the zone valve so the pump can circulate the water when the zone valve is off but when heat is needed then it allows the flow in. A single blending valve at the tank “may” work, but if you are going this route you definitely need to isolate each manifold with a 2 port valve. As a complete random thought, the other trick could to be to use a 3 port diverter valve on each manifold, when it was activated it would open the flow to the buffer, closed would be a “closed loop” so the pump can recirculate and even out the slab etc.... Hmm... ?.. that removes the need to try and balance a bypass valve, and these do have a habit of squealing under low pressure.

I worked on electricity deregulation back in 1997 and back then you could set up an electricity company with one man with just a fax machine and a phone. The core of the DTC hasn’t really changed since then, and it’s only the access rules and requirements on entry to the systems that cost money. The bigger issue is now the way the spot market has changed and trading can be done by the minute, and you could find yourself on the end of a huge liability if the price went to zero or below on a sunny, breezy day where the renewables input overtook the market capacity. If you’ve agreed to buy at 3p yet you’re getting zero back, it wouldn’t be long before you could end up several £k in the red.

Thats why I would leave the gaps between the panels - otherwise you have a very large kite ..!

I’d just put a short piece of nitrile foam tape on the unistrut where they touch and that should stop any issues.

Yep a little. That’s why the fixings are designed to not be tight - they allow the panels to move slightly as the frames expand and contract.

Scaffold poles and Kee clamps would be cheaper and stronger at that price

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 wouldn’t bother relying on Loxone or anything similar to control the actual flow temperatures - they are too long a time constant to use with something that can do 0.01c changes. Just get it to do the on/off and then let some decent thermostats do the room temperature control. And trusting an EPC consultant to design your heating system is like asking @Nickfromwales to do your interior design .....