Dillsue

That's my understanding of how things can be configured. I'm in the throws of setting ours up and currently have it configured to run and stop on a volt free contact which is the same as an on/off stat. Once all the hydraulics are sorted I'll be moving onto WC(AI in LGs world) with the volt free contact acting as a temperature limiter or to disable the HP for other reasons. I could leave the volt free contact/stat disabled with a dip switch and the HP would just pump water as required by WC/AI

Isnt the default set up to use the room temp sensor built into the remote controller?? An external/3rd party thermostat, if fitted, has to be enabled with a DIP switch

If your trip voltage is configurable get them to raise it a couple of volts so you don't keep shutting down. Theres a pretty good chance that the voltage rise is just within your property and if you measured it at the point your cable connects to the grid it would be within tolerance. You can check by measuring the voltage at your neighbours incoming connection when you're exporting on a sunny day, assuming they'll let you! Get them to turn off any big loads when you measure the voltage.

If all your scheduling is done within the Honeywell programmer can you turn that off overnight and see if the HP continues starting up? That will rule out the programmer. If you think it could be the HP topping up the buffer then can you turn the buffer set point temp right down before you go to bed? That should stop the buffer being topped up.

I dont know what series Therma V the OP has but on our series 3 from 2020 the user can bias the WC curve from the indoor display. Should be straight forward to set it up and explain to any user when to tweak things

Let your DNO know and they'll have to do sort it out to keep within the 253v limit

60 ebay results on a search for "heat pump cylinder". Start searching and collecting well in advance of starting a project and most things come up at the right price:)

You could ask Mixergy if they considered or tested that set up? When they went down the PHE route it would have been fairly easy to test things with the PHE outlet feeding in nearer the top. In terms of manufacture its only going to cost a few extra £ to run the outlet up the side of the cylinder to the top, if it gave a performance advantage.

More than happy for your input. You're wanting to do fundamentally the same as me so interesting to hear your take on things. If your morning heating regime is based on cheap overnight eleccy remember that off peak tariffs are not always guaranteed be available....build in flexibility if you can

I'm sure they have more knowledge and experience than me

Our cylinder is 2 metres tall with a mass of pipework above and around the top so access isn't the best. Nearer the base is largely clear so less buggering about to put the return where I beleive/hope it will perform better. The flanges aren't cheap but not needing a 2 port valve for top return will pretty much offset the cost of the flange

?? If you don't want mixing at the top wouldn't you put the flange lower down? Mixergy have their return point around a quarter of the way up so I'm following their lead.......they've likely done extensive testing so I'm trusting that their positioning is optimal??

ASHP pumps through the PHE primary side in the same way it would pump through a coil in the cylinder. On the secondary side a potable water pump will draw cool water from the bottom of the cylinder via the cold water inlet. The pump will pump this water through the secondary side of the PHE. Heated water leaving the PHE secondary will be injected back into the cylinder via the Essex flange fitted part way up the cylinder. I'm aiming to fit the Essex flange about a quarter of the way up the cylinder to avoid the coils inside the cylinder and any seams

75mm of spray foam. Looks a bit of a stretch for gland pliers/pipe wrench so will need to find a box spanner or deep socket to tighten up the back nut

I watched Rogers video earlier and it does look straight forward and not as uncommon as I thought it was. I think Roger mentions a max temp of 60 deg C which is too low for us as the solar thermal can take the cylinder well above that. I had a look on the manufacturers web site and it says up to 90 deg C so a bit of investigation needed. Thanks for all the ideas and comments so far

I'm slowly coming round to the challenge just to get the HW entering in a better place. It's only 5 mins with a holesaw..........what could possibly go wrong:)

Be nice to be able to add a dedicated new tapping but the jury's out on that just now

Waiting to hear back from the cylinder manufacturer on viability of doing this. I'm sure it'll be a negative response but interested to know how they would add one in the factory..... I think they are soldered which is a bit of a none starter with spray foam insulation

Exactly. When we added more PV our DNO stumped up for a new transformer, 3 new poles, 100metres cable, pole anchors, earth loops etc. That brought the supply up to modern standards. The neighbours now run through the summer days on our PV. It's also meant that when we recently applied to hook up an EV charger and heat pump the supply was up to spec and got approved in a couple of days. I would imagine that much if not all of the cost of upgrades to hit net zero are coming from the bill payer and central government so minimal cost to the DNOs??

That's the G98 limit that everyone has a concession to export. If your voltage is going over 253v and it's concerning you then let your DNO know and they'll sort it out for you.....they're obliged to if your sticking to 3.68kw of export.

Before parting with your cash, have a read of what @JohnMo said up thread about nearby restrictions. Might be worth standing a pallet in front of your HP for the winter and see if it impacts operation before paying for and fitting something permanent

I think/hope that there's more resistance through the PHE route than through the cylinder so most HW draw off will be through the cylinder. Via the PHE there's 2 x 22mm Tees, the pump and the PHE but via the cylinder there's nothing but the cylinder itself. I'll leave some space for a 2 port valve just in case things don't work out. I looked at the Mixergy set up and as JohnMo says cooler water is drawn from the bottom and returned around a quarter of the way up. Would be nice to replicate that setup but I'm a bit wary of cutting a new hole in the existing cylinder and then feeding a new tank connector through the immersion boss and getting it into place and secured. Anyone successfully done that??

Thanks for the tip about counter flow....not sure I would have considered that. Not sure I follow where you're suggesting an NRV is needed? I'm going to pump from cold inlet, though PHE and into the HW outlet. I cant fit an NRV to block that flow when the pump isn't running as it will block the flow when the pump is running???

Shutting down at 253.6v seems overly close to the limit....my 2 solaredge inverters dont trip til they hit 262v. If that figure of 253.6 is adjustable, I'd raise it slightly whilst you sort things out with your DNO G98 allows you to export up to 3.68kw without seeking permission and your DNO should ensure that when exporting at that rate that your voltage stays below the 253v limit. If you're going over 253v with 2kw of export, things will only get worse with more export. As a minimum your DNO should ensure you can push 3.68kw into the grid and stay below 253v. Is your installer putting in a G99??

On a calibrated Fluke we're currently sat at 251v with minimal load in the house and negligible PV export as its grey and raining. A good chunk of PV export will push that to the 253v limit and a touch beyond at times!