MikeSharp01

No room! I have 60l and a massive slab, no radiators, so although the heat transfer from the slab back into the water is not as good as on the tank the temperature drop is still only fractions of a degree for a 0.8kWh defrost 0.06 deg C if my calcs are correct.

I was thinking about this on Thursday when I realised that our system volume is only enough when the Underfloor Heating (UFH) is in the loop when its just running through the domestic hot Water (DHW) tank the volume is a lot less. However I also feel that as far as the DHW tank is concerned the heat transfer is roughly reversable, I guess entropy and a few other factors will have a part to play, so the hot water in the tank will give its heat up to the circulating HP circuit and so all will be well. I dimly recall working out that we might need ~0.8kWh for a defrost, if all that comes from the Tank - because the other volume in the system during a DHW cycle is only around 31l (Including the tank coil) we would see a drop in water temperature of a few degrees which may or may not be a worry depending. (To use that side the heat pump will be in DHW mode so a set point is engaged somewhere and defrosts could result in it getting in loop trying to reach set point while being knocked back by defrost cycles). When the slab is in the loop and based on the same assumptions as for the tank defrost the temperature drop is a fraction of a degree across the slab, the systems volume then is around 60l, the slab is 60T of concrete and there is no close in setpoint to worry about.

Depends which end of the telescope you are looking down so either a great way to while away a decade and spend loads and loads of cash or a tiny thing not remotely likely to be a problem and still a very long way off.

The wisdom of crowds - used in ensemble method AI models (random forests) so yet another example of an old idea (Aristotle understood it) getting a new lease of life as part of AI, along with Bayes Theorem (1761) and the Neural Network itself really stemming from the 1950s development of the perceptron.

Yep - you get today's prize. The drawing is crap, makes you wonder how good this stuff is. Your right I will be running mine at 1.5 bar - enough to meet the spec of the heat meter but no so much as to blow the socks off.

The heat pump install proceeds at pace, well two steps forward and one back mostly. Todays one back is this filling loop I got from the plumbers merchant. Allegedly it is automatic, you dial up the pressure you want, open the valves and once it has done its business you close the valves. See if you can see anything wrong with the instructions and the parts as supplied.

Yes that makes sense. So "b. be a separate branch pipe with no sanitary appliances connected to it;" means (not implies) the D2 pipe is a branch pipe itself? Hope that helps @Nickfromwales

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.