Adding PV and Battery System to existing fits PV install - DNO involvement.

[martinW]

Ah...

That cleared up the confusion.

I knew the inverter stops exporting when there was a loss of the grid power. I thought that when it powered the house via the batteries when grid was down was called island mode.

Obviously not... no wonder I was confused.

[billi]

Thanks for all the replies.

I will go down route of Sofar ac Coupled inverter and notify DNO of the inverter and batteries only. This will complement my existing 3kw solar PV.

Then once approved/ sorted I can add a DC PV charging system for the batteries.

Well, that route sounds good to me

There should be no limitations for people installing more PV beside their FIT contract (that is made over a time span off 20+ years) .... in those days

[Moxi]

#21 by martinW » Wed Feb 02, 2022 12:45 pm
Ah...

That cleared up the confusion.

I knew the inverter stops exporting when there was a loss of the grid power. I thought that when it powered the house via the batteries when grid was down was called island mode.

Obviously not... no wonder I was confused.

martinW I could be very wrong but I think the Sofar ME3000SP separate (Off Grid) circuit will only power whatever sockets are connected to that output - its not connected back to your consumer unit and therefore cannot power the whole house in the event of a grid outage.

Moxi

[nowty]

martinW I could be very wrong but I think the Sofar ME3000SP separate (Off Grid) circuit will only power whatever sockets are connected to that output - its not connected back to your consumer unit and therefore cannot power the whole house in the event of a grid outage.

Moxi

Correct.

[martinW]

#21 by martinW » Wed Feb 02, 2022 12:45 pm


martinW I could be very wrong but I think the Sofar ME3000SP separate (Off Grid) circuit will only power whatever sockets are connected to that output - its not connected back to your consumer unit and therefore cannot power the whole house in the event of a grid outage.

Moxi

I intend to wire the sofar emergency output to dedicated ciruits (maybe in own consumer unit), such as lights, etc.

[Stinsy]

#21 by martinW » Wed Feb 02, 2022 12:45 pm


martinW I could be very wrong but I think the Sofar ME3000SP separate (Off Grid) circuit will only power whatever sockets are connected to that output - its not connected back to your consumer unit and therefore cannot power the whole house in the event of a grid outage.

Moxi

I intend to wire the sofar emergency output to dedicated ciruits (maybe in own consumer unit), such as lights, etc.

That's how I'd do it!

Lights are a no-brainer, just double-check there are no old-fassioned filament lamps, or 150W spotlights, halogen downlights, etc., and check for bathroom extractors that might be on the lighting circuit. Your total lighting load with everything on is probably less than an amp!

Next it is worth wiring your boiler, fridge/freezer, wifi router, and a couple of key sockets onto the "UPS" circuit. Maybe one for the TV, one to charge your phone/laptop.

The other thing to consider is how much power to "reserve" for UPS operation. If the power goes down just as the cheap period ends you're fine, same on a really sunny day. But guess what? The power tends to go off in the evening, in winter, when your batteries would be depleted. to cover this you can set your inverter not to discharge below 40% (for example) when the grid is live. However that means you're getting less payback from your batteries in normal conditions and will need a bigger battery pack to avoid peak-rate electricity usage in winter.

[nowty]

I intend to wire the sofar emergency output to dedicated ciruits (maybe in own consumer unit), such as lights, etc.

Unless you know what you are doing it gets complicated especially with respect to earthing so you may be better off just having a gang of sockets to plug in individual devices. Some devices like table lamps and phone / laptop chargers, etc, don't even have an earth, so very little risk.

If you do want to wire up some critical circuits and make it automatic, then this is from the Sofar ME3000SP manual of how to do it with a 4 pole 2NO 2NC contactor.

£20 from china via ebay for an equivalent device. -https://www.ebay.co.uk/itm/224621197559 ... BMrvfM9tdf

[wookey]

This is a very useful thread.
I too am looking at getting a battery. I've never bothered before as our usage was so low (~800kWh/yr), but now we are at home all day and I have some more kit it's gone up to ~1600kWh/yr and the prices are doubling it seems worth doing so we could use more of the 85% we currently export. We currently have a 2009-installed 2.9kW PV system on initial FIT rate.

Now this page says I can just replace my inverter and the FIT people don't care: https://redelectrical.co.uk/solar-pv-pa ... er-myself/ but I guess that's just like-for-like, so swapping the existing string inverter for a hybrid and adding a battery would be different. This is what an installer who came round suggested: bin my 3kW Fronius, and put in a sofar 3kW hybrid inverter and 3.5kWh of pylontech batteries.
Seems to me that's a reasonable spec, but the FITs people will have something to say about that because the battery would be behind the generation meter?

Also I don't really like the idea of binning a perfectly good Fronius for a cheapo Chinese inverter and it would make more sense to fit an AC-coupled battery with it's own inverter, and this thread tells me I'll have to ask the DNO to do that. The Fronius is installed indoors rather than outside or in a loft so has had a very comfortable life. It's done 12 years so far, and will probably manage few more yet.

There is presumably some chapter-and-verse on all this which I should read?

I see loads of you have the pylontechs and they seem like good gear. I'm just trying to get my head around the various nuances of AC/DC, how to have some critical load circuits, choice of inverters etc. Oddly enough this forum has much better info than most of the rest of the net, although I did find a couple of useful people on youtube.

[Andy]

I would say don’t be scared of the DNO process. I’ve just done a g99/g100 application myself for a 10kVa Victron with batteries. The forms are not very difficult. I feel a small battery setup with g100 export limitation is almost a formality. There is usually a fast track form for the small set ups . Unfortunately I fell well outside of that but it wasn’t too onerous. The people at SSE I spoke to where very friendly and approachable. As far from jobs worths as possible which is refreshing having dealt with other complete idiots in other industries that made want to tear the hair I don’t have out of my head.