Dillsue

It was the integral PW one that triggered the 2 inverter discussion earlier!

Speak to them first as you may get an indication of likley export limits without making a formal application. SPEN did an informal assessment on our limit and we had an agreement in a few days. Sent the formal G99 application in to reflect what we'd already agreed so straight forward approval. Not sure all DNOs are that slick though!!

Theres a DC-AC inverter in the powerwall on top of the SE PV one!

Is that a UK spec G99 compliant inverter?? AFAIK that feature wont be in a UK spec inverters firmware???

You can do all of those things. Plenty of good schematic diagrams and write ups on the web BUT... If youve read that grid tied systems cant have batteries you need to be a bit more choosy where you get your info as that is wrong. Make sure you are looking at systems for the UK market as our rules differ to other countries. Have a look at "Solaredge storenergy" for a DC coupled hybrid system. Have a look at "Tesla Powerwall" for an AC coupled battery pack. Lots of other manufacturers, but those two have good schematics.

No. Both the grid and your inverter feed your consumer unit and the power from either or both feeds the house circuits fed from the consumer unit. Your inverter is connected to an MCB(maybe fuse) in your consumer unit in the same way as all the other circuits in the house. The difference being during daytime power flows from the inverter TO the consumer unit rather than power flowing FROM the consumer unit for all other circuits. At night when the inverter isnt generating, a small amount of power flows TO the inverter. None of the circuits are connected to the busbars

Absolutely not. It MUST shutdown or it could electrocute someone trying to repair the cause of your power cut

If Octopus are supplying you, then youre connected to the grid. If your inverter is connected to the consumer unit, then its grid tied. Anytime your inverter or batteries cant provide the power you need, the extra will be drawn from the grid

Whether its worth it is entirely up to you then. Depends on how much, if any, ROI you want, when your gonna move in, how easy to charge your EV etc etc

Op wants power in a power cut and is already talking about a Powerwall which will provide power in a cut but wont process PV, so 2 inverters. Im not sure if theres any UK certified systems that will do backup and process PV?? I think Solaredge already have PB/backup inverter certified for the US but not the UK yet. May be there are other systems??

If its a DC coupled battery then the batteries output comes through the inverter and is limited by the inverter. If you go for an SE3680H, the DNOs limit, with an SE battery then the PV and or battery output to the house/grid is limited to 3.68kw. Your DNO wont care if the power is coming from PV or battery, so long as its limited to 3.68kw. You can have as much PV or battery capacity as you want so long as the inverter limits output

As a holiday let is it part of your property and on the same supply as your house, or on a separate supply? Our original 4kw system was modelled at 3400kwh/year and has done 3500-3700kwh/year since 2015

Are you sure they said 3.68kw of panels?? DNO is usually only interested in the inverters max output and does care how many panels you have. Its more usual for DNOs to say you can have an additional 3.68kw of export which is governed by the inverter you choose. If that is the case then an SE3680H can have 5.7kw of panels connected to it, more if they are facing differing directions. Whats the maximum additional kw capacity you could get on your roof in each direction, including the FIT system panels?

Youre only tied to SE if you want DC coupled batteries. AFAIK you can have AC coupled from any supplier

Yes, but thats what youve got now with your 5kw inverter limited to 3.6kw. Using the correctly G98 certified inverter saves you the G99/G100 application and cost

Technically all correct, but.... With only 4.5 kw of panels youre unlikely to cause anyone any problems so I wouldn't rush to disconnect. Id ask youre installer why he installed a 5kw inverter as a quick look at a Solis 3.6 inverter says it can have 7kw of DC input. Fitting a 3.6kw inverter would keep you within the DNOs G98 limit and you wouldnt have the issues youre asking about. If you want to keep the 5kw inverter then youll likely need a G99 application with a G100 supplement to cover the export limitation. Our DNO charges to witness the export limitation is set correctly! Id put this back to youre installer to answer a few questions!!

Yes, I think youre correct- I forgot you want batteries aswell. If the CT is for battery charging I think a wireless CT is fine. I think that a cabled CT is only mandatory where your export limition is part of a G99/G100 compliant system. Definitely worth checking before you commit to any scheme.

Youd only need a CT if going down the route of export limitation to keep voltage in check. If running additional/upgraded power/comms cables isnt an option then choices to keep things above board seem to be- Use an inverter with voltage controlled power throttling Run DC down the SWA and have the inverter at the house rather than with the panels, subject to the 6mm/120m cable being up to it and having the correct voltage rating. Obviously lots of other solutions that may not keep things strictly above board.

If the voltage goes too high it will trip the inverter which probably would be an issue. I just reread what you originally said and spotted that youve got another 50m of cable to the DNO service connection which will give you additional voltage rise over whatever your DNO is giving you. Not sure if the Solis inverter has a similar feature but Solaredge HD wave inverters have a power control function that can be voltage controlled so as the voltage rises the power generation is throttled. That would keep voltage in check. Another option could be to put in zero export limitation so the inverter will only supply battery charging and the house load and throttle generation if theres no charging or house load. That would remove any voltage rise caused by the 50m from house to service connection.

We run at no load voltage of 250vac. I was told a while back our DNO runs it high to get more power through the system rather than lower us to UK spec of 230vac with increased current and the need for beefier cabling everywhere. Starting at 250vac means our original 4kw system pushes the house over 253vac and the new system way beyond that.

But.... the problem, as prodave mentioned, is voltage rise and that is specific to your situation. It depends not only on your cable length/size but on the power(current) you are trying to push down the cable and the supply voltage to your house. UK supply voltage can legitimately be anywhere from 216-253vac. If you start with a high voltage you havent got to cause much of a rise to go outside those limits, but thats somewhat up to you and/or your electrician. The problem is if you get too much of a rise your inverter can trip. If you are charging batteries then thats unlikely to be a problem, but once the batteries are charged on a sunny summers day, it could be a problem. Best to get your electrician to look at things and do some calcs for you

I thought you were getting a new system installed? If thats the case tell the installer not to register the system and you do it on your account, I didnt need an inverter serial number to open an installers account. When my daughters hubby registered their system, two of the optimisers had been previously registered- they were bought as NOS but clearly their serial numbers had made it on to the SE portal at some time. Over a day or so the optimisers were accepted and now show up on their system. I guess the SE portal checks to see if theres any data coming from the originally registered system and if there isnt, allows them to be assigned to a new system? My second system is using a secondhand inverter so I expect the same temporary issue once I get an internet connection to it and register the system.

Register an installers account with SE?? I have a homeowners account for our original MCS system that was set up by the installer at the time. Ive opened an installers account to add our second DIY system to their portal once I get an internet connection to the inverter. My daughters hubby opened an installers account to add their DIY system to the portal. No batteries in any of those systems so I cant say what can be configured through the portal. I think once youve opened an installers account youd be able to log onto Setapp and use that to configure the charging??

Maybe, but the OP is saying 4 batteries on each inverter and 4 x 48vdc wont give the recomended 300vdc the inverter is looking for. Im not up on battery tech but do know that theres "high voltage" PV batteries around which operate at several hundred volts which maybe what the OPs inverter is intended for?? Solaredge Energybanks operate at 350-450 vdc which matches the typical incoming DC from an optimised set of panels which the energybank is directly connected to. Maybe the OPs set up is similar??

Look at the inverter and battery voltage- big mismatch. If the inverter is expecting a 300vdc battery you can use much smaller cables than youd expect to see on the 48vdc battery. A 10kw solaredge battery connects to its inverter with MC4 connectors and that pushes out 5kw sustained and 7kw for short bursts, all through MC4 connectors.