G99 schematic - help and advice appreciated (UK based)

[pattisd]

Hey Guys,

I had an installer provide me with a 3kwp solar array and SolarEdge Inverter about 12 years ago. I get FIT payments for this setup - so Its already paid for itself but with the increasing cost of electricity I was thinking it would be good to add a battery to save whatever power I didn't consume and also look to charge the battery "off-peak" with one of the lower rate energy tariffs.

As I don't want to jeopardize the existing FIT, it looked like and AC coupled inverter and battery were the way to go. I am with Octopus Energy too and have considered an EV purchase to allow me to get onto their Go tariff.

I was looking at the Victron kit (5kwp) as one option and the SunSynk (8kwp) as the other.

I eventually decided on a DIY 48v LifePO4 battery along with the Victron Kit. So I have purchased the following:

16 EVE 3.2v LifePO4 cells 280Ah.
JK BMS (JK-B2A24S).
Victron Multiplus II 48/5000/70-50.
Victron Cerbo GX
Victron Current Sensor

I have built a housing for the cells so they are under compression and now am about to find an electrician (Part P qualified) to install the AC side for me.

I am aware that I need G99 approval from my DNO - SSE. And also aware of the issues that Victron have faced getting their kit re-certified and marked as compliant on the ENA type test register. I've not seen any G100 certificate for the newer regulations - so wasn't sure if one exists or not? (Sadly I see the Sunsynk kit is now G99/G100 compliant - so wishing Id chosen that route - given where I am ... but not certain these cells/BMS are a great match for that system).

I have been trying to build a schematic that could be used for the G99 application.




And was wondering if anyone could review this and add any value by advising what needs to change to make the install better.

I am looking for the Victron to provide backup power via one Consumer Unit which would power the majority of the house (I'm aware the loading would need to be kept light) in the case of grid failure.
In normal operation, I'd want any excess power generated by the existing SolarEdge to be absorbed by the battery. And for times of the year when there is very little solar, I'd want to force charge the battery on an off-peak tariff.

I want to allow for maintenance of the Victron Inverter - so have added AC isolation. And when this is out of operation I have added a change over switch to allow the maintained load CU to be powered from Grid as opposed to the Victron Inverter.

I've also added an earth rod. Don't know much about the differing types. But I understand for the Inverter to run in backup mode it does require a discrete earth. Is there anything specific I need to state for this aspect?

I've been trying to read lots of posts and gather info from others in similar circumstances and apply all that I think I understand. But at the end of the day I am a novice and want to ensure this is done properly. So, I really do welcome all constructive advice.

I still have a dilemma how to proceed. The Victron inverter isn't yet approved and its been like that for months now. So could I get the electrician to install everything but put it into "maintenance" - so that its isolated? Or is it best to wait for G99 certification? What would happen if I applied for G99 with the DNO currently? Would the application just get rejected? Can I set a commission date well in the future when certification might be available?
And what do folk think is the likely outcome as far as certification goes? Will this inverter ever qualify in the UK?

And the original install was done with G98. But that inverter is no longer supported. Would the DNO raise any issue with that? It certainly won't have a G98 certificate to match the current regs.

I think the "fast track" G99 route criteria has changed a bit too? But I'm not sure I understand the differences. Would my proposed amendment qualify for fast track now? It certainly didn't under the old fast-track definition.

My existing setup has 3kwp max - its a small (and old) inverter. And this can't be controlled by the Victron to explicitly control export to the Grid. So does the Victron need to be limited to 3kwp export? That would allow the SolarEdge to be working at full capacity and the Victron not to supply any additional power. Eventually I may like to add DC coupled Panels to the Victron Inverter via an MPPT charge controller. That would mean i could potentially charge up =more of the batter capacity via Solar rather than having to force charge the battery overnight (so keeping costs down). But for a lot of the year in the UK I doubt that would have a major effect and I would always have to rely on significant forced charging in Winter.

This brings me back to the G100 certification. I did see this in one of the old Victron documents somewhere. But I've not seen any mention of this more recently in the attempts to get the G99 certification approved. So if some grip limit is imposed should i ever get approval, how is this demonstrated or achieved?

Many thanks for anyone who is able to help me out.

Cheers all.

[Countrypaul]

I'm not an electrician, and don't yet have a battery setup - but have been looking ad a Victron and batteries for similar reasons to yourself.

1) You show an export meter I think you mean Total Generation Meter if this for FITS as you are nomally paid for generation and deemed Export - could be confusing.

2) What is the point of the ET112 meter - it should be producing exactly the same results as the DNO meter.

3) Are you aware that you can couple your existing system into the Victron output to AC couple and allow the existing system to contribute even during a power cut? Some information here: https://www.victronenergy.com/live/ac_c ... y_capacity

Just my tuppence worth to get started.

[nowty]

Not much to add really, looks very similar to my own setup with SMA kit, looks like you know what your doing.

With regards to Victron Multiplus II 48/5000/70-50, still looks like awaiting assessment,
https://www.ena-eng.org/gen-ttr/
https://community.victronenergy.com/que ... pdate.html

With regards to G99 application, fast track has recently changed and there are now 3 flavours, SGI-1, SGI-2, and SGI-3.
https://connections.nationalgrid.co.uk/ ... track-g99/

I guess your DNO is SSE, link for SSE G99 fast track process,
https://www.ssen.co.uk/our-services/new ... k-process/

[dangermouse]

Just a minor point, you don't need an EV to be on the Octopus Go tariff.

[sharpener]

Looks pretty good to me.

As @Countrypaul says, as you haven't got the DC coupled PV yet I would (and did!) connect the existing PV to AC-Out for the reasons he gives. The existing SolarEdge setup will probably have the old G83 certification (and the DNO should accept that). In that case the Victron will shut it down in island mode by frequency shift, you may have to experiment a bit with the settings, have you got the manual? I wouldn't show the future DC-connected PV on the applicaton diagram, it made WPD's brain hurt so I had to delete it and re-submit.

What non-maintained loads do you have in mind? EV? Yes, you need your ET112 to achieve grid balance, but a CT is cheaper and quicker acting, where does your "Victron current sensor" go? You also need a second ET112 in the feed from the existing PV or the Victron dashboard won't show the generation correctly though it will all work.

The MCB at [1] needs to be a 30mA RCD or RCBO as leakage current detection is a requirement for the inverter feed, however if is lockable you don't need the separate isolator below it.

Yes you should show the Cerbo as it is part of the Export Limitaton scheme. I expect Victron will sort out the certification in a month or two but I wouldn't apply until it is resolved.

Earth electrode should have a resistance of 200 ohms or less, not hard to achieve with the kit available from any wholesaler, your spark should know what will work in your locality.

PM me if you want to and good luck with it all.

[Andy]

If you are putting the SolarEdge on AC Out then I would recommend putting it on AC Out 2 so when the grid goes down the Solar Edge is disconnected. I then have a change over which connects everything on AC Out 2 back to AC Out 1. I discovered my SolarEdge won't throttle to raised frequencies from the Victron. This at least for now allows me to decide if I need the extra solar production from the Solar Edge and can manually reconnect it when safe to do so. If left on when the batteries are full it would be a very expensive destruction of everything. I have had to have my installer rewire from AC Out 1 to AC Out 2 because of this. Also worth putting loads like heat pumps/carchargers on AC Out 2 so they don't deplete your system too fast.

[Andy]

If the inverter is in line with everything. ie Grid -> Multiplus -> ACOUT loads -> Consumer unit. An RCD on the input side would have all house loads/chargers/solar edge contributing to the 30mA cut out. Wouldn't that cause issues? You could have very small leakages within limits on all the other circuits but the RCD on the input to the inverter would always trip.

That's assuming things are reworked to have all loads on the various AC Outs

[sharpener]

If the inverter is in line with everything. ie Grid -> Multiplus -> ACOUT loads -> Consumer unit. An RCD on the input side would have all house loads/chargers/solar edge contributing to the 30mA cut out. Wouldn't that cause issues? You could have very small leakages within limits on all the other circuits but the RCD on the input to the inverter would always trip.

That's assuming things are reworked to have all loads on the various AC Outs

That's a good argument for leaving the non-critical loads as they are rather than moving them to AC-OUT2, the functionality is much the same. Also it keeps them from eating into the 50A passthrough limit. The RCD on the inverter input is mandated by the IET CoP and of course the OP's electrican will be familiar with that <g>.

[NikoV6]

I have Tesla Powerwall set to never export to grid and 10kw of solar, limited to max 3.6 kw export by G99 and G100 certified Solis inverter

I spoke with Scottish Power and they said G98 application was sufficient

I sent schematic, and G99/100 certificates with G98 application and have only had the email back from them confirming application and that they would be back in touch if they needed further information. Nothing heard since

[Ronski]

I applied for my own G99 last year with UK Power Networks, I simply filled the form out stating existing system 3.6kW SolarEdge from 2015, and an additional system, consisting of a Quattro 48/10000, I never stated any export limitation, or sent any schematics, and it was approved. I will need to send a schematic once commissioned, along with other documents. Incidently the the electricians are here today to do the AC work. I'm running the whole house through the Quattro.

For your install I would not specify zero export, wait and see what they approve, there may well be quite a bit of money to be made from exporting.

The Quattro was re-certified on 17th January, I'm sure the 5k Multiplus will follow soon.