Dillsue

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!

If you look at the voltage line through the night you can see it rises as everyone gets into bed and the load reduces. Around 6am the voltage starts to drop as people wake up and the load increases. As your PV starts to generate around 7 you can see the voltage start to rise and then drop off as your generation drops off. You can see your PV pushing the house voltage up as it generates. The rest of the fluctuation will likely be the load from you/your neighbours being awake and using stuff??

I'd heard that in certain areas, maybe with higher than average PV installations, that they seasonally change the tappings to lower the voltage in the summer and raise it in the winter. No idea if thats a fact or not but it seems logical to keep local voltage within limits.

A higher supply voltage wont stop you exporting. Whatever your connection voltage is your inverter will raise the house voltage a little so power will flow out of the house and into the grid.

Well over 240v is perfectly normal. It's the DNOs way of getting more power to you by upping the voltage rather than the current. Our no load voltage is around 250v and tickles the max of 253v on a sunny day when the PV is going full chat. The move from 240v to 230v was when we harmonised our voltage with Europe....they were at 220v and we were at 240v so we met in the middle

No apologies needed. I was a bit confused by what you were saying but all is clear now.....for both of us

The DHW circulation pump will draw from the cold inlet at the bottom of the cylinder, pump through the PHE then inject the heated water in at the top. That way it circulates cylinder contents through the PHE, pushing the hotter water in at the top. Primary side of the PHE is pumped by the ASHP

I tried using the existing .44m2 coil and it was hopeless so have resigned myself to fitting a PHE. There's likely a few ways I could trigger the DHW circulation pump but anyone know of proven ways?

My guess would be that fires related to isolators would be due to loose connections rather than the switch contacts. The switch/contacts are extensively tested by the manufacturer. The cable terminations are installed in an often awkwardly small space and likely the only testing is a gentle tug to make sure some of the cable has has been caught in the terminal. My money would be on improperly terminated cable, likely without crimps where there should be, or the fine stranded PV cable settling in the clamp over time and coming loose.

Exactly......no point in scaremongering over what is a negligible risk