MikeSharp01

I guess I will look into that but I suspect it will be simpler just to put a stat on the manifold in the ASHP enable line to shut it down if the water temp at the manifold gets too high.

How so?

Spent the day working through Failure Modes and Effects Analysis (FMEA) of our ASHP system. I have hit on one which has me wondering if I have missed something. When the ASHP goes to heat the Domestic Hot Water (DHW) it provides a voltage to the changeover valve in the house that switches the ASHP flow from the Under Floor Heating (UFH) circuit to the DHW heating circuit. All well and good except that there is no feedback to the ASHP, that I can spot, that confirms the valve has actually moved and the the circulation is now running round the DHW circuit. In the situation where it fails to change over we will get the much hotter water, normally reserved for heating the DHW, flowing into our UFH which as a strict upper limit on the floor surface because of the floor coverings. There is a temperature probe feeding the DHW cylinder temperature back to the ASHP but the lag on that could be significant even supposing the ASHP has a mechanism for detecting that there is no rise in temperature of the DHW despite it apparently delivering 55oC water to the cylinder. This seems like an oversight to me, have I missed something or am I expected to provide an external solution - any thoughts or observations?

I did think about installing the TMV directly above the tank outlet but decided it made everything more messy so its just at the edge of the tank. Not many but if it saves me having too much heat loss into the Utility room, where all this kit resides, I might just create a loop as you suggest. Sorry not clear what you mean, you can get my pump onto the Schrader valves of both vessels as they are placed in the picture, the view angle makes it look like they are very close together or are you referring to something else? There is no room below the large vessel for one of those service valves but I could put the valve to one side or possibly lift both vessels up but the upper one will start to interfere with the hot and cold water manifolds which will be above it. Alternatively I could mount the large vessel horizontally if that is allowed?

Does that not gain say what @SimonD says he always fits by way of a service valve.

Oh - I was hoping to go into the main soil stack, center in image, in the corner of the room but if not I can round a bit and use the branch stack, right of center, which has nothing attached.

No secondary circulation but need the TMV if I top up the UVC to 80+ with excess PV.

Yes it's in a cupboard.

That's already on the top of the small vessel should I also fit one to the big one?

The Umbrella company are doing that alongside the MCS cert, hence me asking all the questions so I get it right and don't end up with problems.

I am working on the tank end of the system now and that has thrown up some clarifications that I need to be sure of: Can I install the Thermostatic Mixing Valve (TMV) upside down as shown in the picture. (Cannot see what gravity has to do with the operation of such a valve) In connecting up the various overflows and the condensate drain from the Mechanical Heating and Ventilation Unit (MVHR) above the tank I need to get the final output into our main soil pipe. How far should I run it in copper? (As far as possible as you want it to cool down before it hits any plastic) How important are the details of the runs to the tundish(s) - seems like there is supposed to be 300mm of straight pipe into it etc... (I need to get the three pressure, one of which also has temperature, relief outflows into the pipe above the tundish.) Or would it be better / acceptable to go for three tundishes and join the flows below them? How do I connect copper to 32mm waste pipe? (Cannot seem to find a connector for this - do I make one from a blanking cap and tank fitting or some such? I did find this https://www.toolstation.com/tesla-tundish-universal-dry-trap/pAG239 but that goes directly from Tundish to 32mm so no room for cooling.) Can I get away with a waterless trap or do I need a full U bend in the plastic bit? (Waterless makes sense because it will get very little use so a U bend could / would dry out) Is there a waterless trap for 22mm Copper perhaps? As you can see from the image I have not yet connected the Heating loop from the ASHP to the expansion vessel. I assume it does not matter where in the heating circuit I make that connection as pressure difference arising from heating in the Domestic Hot Water (DHW) Loop and the UFH loop will manifest itself everywhere in the circuits. (I have no room for the expansion vessel elsewhere but I can run a long pipe to it from wherever in the circuit if needs be.)

They sound about OK to me. Our costs were (IIRC): Re-route Electricity from old house overhead to utilities block by the pole (pole on our land) down the pole along a 400mm trench, which we dug, and up into the meter box: £1200+VAT (2018) Move gas from the old house, which we knocked down, to utilities block in trench we dug and then remove it completely when we decided not to have gas £840+VAT (2018 / 2021) Do you really need Gas, might be worth working out if a ASHP might be a better solution if you are building a well insulated / air tight property.

I like that you have Ned Kelly wearing his metal head gear working there in the middle with the green high viz.

Metric.

The thread on gauge does not appear to be standard, 1/8th BSP vent does not fit, I will talk to the suppliers and get a new end cap assembly as the flow head.

Sadly that would require a complete redesign and there are loads of other pipes - mains water, water softener etc, running in those areas I have not installed yet so two filters is easier. I have the connections for that coming Monday to the far left of the straight run from the return manifold That's already in the return line from the tank out of shot to the left. Its not 25l though it 8l which should more than cover the 70l of the system I worked out.

Here is the plant room mockup plumbing (used 28mm plastic segments to get lengths right and check scheme). I think I can get the filters into the utility room as indicated, I either do away with the fill flush or put it outside by the HP and work hard to insulate it.

I will send some pictures in the morning.

I think I have a full flow filter. It's this one:

So I am going to have house them both outside.

Thinking about it I cannot put the valve inside either as it would have to be in one side or the other of the system.

Does that mean the stainer has to be inside as I have nowhere to put it inside. Pipework splits as it comes through the wall.

Your budget is not unrealistic for 80m2 and if you are into it for the long term you can do a lot of the work yourself and pay for it as you work. The up front lump will be your plot cost!

Thanks, how do you put inhibitor etc in, no Glycol. We are but the manifold went in before we chose to go that way, only three loops no independent control of the loops other than by the flow meters which once set are left. That is what I thought.

Radical Thinking - but maybe where we are heading. Our children, in their 30s, will defo not retire before 70!