I have a multiplus II 10kva inverter as a diy installation. I recently found out that i needed to apply for a g99 approval prior to the installation (im in the UK) but to avoid the red tape and a potential rejection from the DNO, is it possible to run my house in an off grid configuration on the mp2, and add a contactor in line with the AC input, that can be set to close when i set the generator start stop schedule to change my batteries over night, then just run the inverter off grid from the batteries? So basically useing the inverter as a charger when grid connected, and as an inverter when the contactor is open. Will i still need a g99?
1 Like
Any how it connects to the grid the DNO’s G98 G99 G100 comes into play depending on kW.
It’s Red tape for a reason.
Who is your DNO, if UK Power Network the application process is straightforward. And quite surprised they let me up my sight to 14kW.
Somethings to take care of before the application find out what the amperage is of the DNO main fuse check to see if you have double insulated 25mm2 tails and a disconnect switch between the meter and the CU if they are anything like UK Power Network they want picture of that area.
A lot of this is going to be dependent on your area how this appplication does
1 Like
My DNO is "natural grid electricity distribution " (south Wales)
Is yours a diy install too?
What was the procedure and costs.
Looks like ill have to bite the bullet, but worried i wont be able to use my system after opening this can of worms.
Hi mate I was lucky my DNO didn’t charge anything, single line diagrams are needed I also done a diagram of (my CU and how it integrate not needed) also sight diagram and I also got an electrical layout of there cable to site.
Ie when you dig you can request the information of cables and pipes it’s a free process so you may get the layout from there then just include where everything is mounted.
PS I know some DNO’s charge for installation of inverters to connect to the grid. I hope this helps maybe give them a call and say you are wondering what the process would be
Can single line diagrams be hand drawn, as im no good with software lol.
Also is yours diy and self tested and g99 self done?
I would do it with software as it will look like what they are use too, you don’t want to come over green. The software I used https://app.diagrams.net/
Yes I installed mine, got a spark to test the AC side ie more the TT side of my build. As that’s a reading they need my old single line is below some stuff will be the same use it as a guide. G99 app
Approved 12.5kW Single Line Diagram.pdf (447.1 KB)
Thanks for the diagram, i must say that looks very complex compared to mine. May i ask what the item is above the rotary isolator left of the inverter? A change over switch?
Also, are rotary isolators critical, as ive used din rail mcb’s which double up as isolators.
Yes it’s a change over switch and yes lockable isolation switch if they can lock then think you are ok but much easier with the rotary.
G99 A1.1 Commissioning Information Provided:
Commission Date: Wed, 01 Jan 2025
Location within Customer’s Installation: Garage
Location of Lockable Isolation Switch: Rear Garage door on the wall and between the inveter
and garage consumer unit at the garage door
When i downloaded the g99 A1.1 form if was only 3 pages long and only showd 3 phase input boxes where you state the inverter power, and no box to state the solar panel power, so i thought i have the wrong form.
I guess it must differ between different dno’s?
I dont suppose you could help me fill ot in if we DM each other? Im at my wits end here lol
Oh i just found out that direct messages are not possible on here, so if your happy to help ill put my email address on here
Is there no online portal? As you can just save it as you go along.
That section is from the commissioning stage of the application first process is can I do it? if they say yes/no, impose restrictions or not that is the first stage.
Don’t ask don’t get, I’ve not seen any other DNO’s requirements some require a fee and testing some just testing others your testimonial.
But as said there are things you need to know early in the app process service head fuse size tail diameter if they say they have to upgrade the Service head fuse to a 80amp or 100amp making sure your install has lockable isolation, ie in the event of fire easy access.
Have a look at the section where people show there build and see what they are doing obviously every country is different on regs
PS if you haven’t got a transfer switch you may want to put one of the system needed servicing, upgrade gone wrong at least the house will still have power just a thought.
The person that helped me was @craigchamberlain and think it’s @Spark not sure if it’s the same person from the old forum, but I don’t really see them on here which is ashame as there knowledge base is extensive and also in the UK
Thanks again for your help and advice, shame craig or spark aren’t reachable anymore. Im feeling this will be a nightmare, ive always hated having to get 3rd parties in on a job, but im thinking ill need an installer to assist me on the testing process and getting that g99 application sorted. I may have to bite the bullet and pay the 4 figure sum to an installer.
Biggest problem is that installers seem very difficult to get hold of, dont tend to touch victron and dont want to touch other peoples installations, so im feeling im in a catch 22 situation.
I think it’s worth it to get G99 too… BUT, you don’t actually have to in the UK as long as you don’t need to use ESS then you can set no grid code in the inverter. It’s then unable to feedback into the grid and is therefore just another load as far as the DNO are concerned, but you don’t get the ESS options, although with DVCC and assistants most things can be accomplished.
This is what we do on boats and houseboats, as we can’t use ESS on plugged connections due to risk of electric shock if the pins are live for a split second during feedback before the inverter realises the cable is unplugged.
I use Ignore AC logic, but also have a transfer switch to select from shore (Grid) or from the inverter.
See this diagram I made for a houseboat system also using diagrams.net:
1 Like
Thanks but my biggest problem is that i need to charge my batteries from the grid during cheap rate and use the inverter off grid via an open contactor connected in series with AC in (i know i can use AC ignore, but the grid is technically still connected to the inverter, but with an external contactor its not) however, even though the mp2 is only used as a battery charger while connected to the grid, ive been told that i still need g99. I have enough capacity to be off grid completely during the peak hours.
If you don’t set a grid code, whoever told you this is wrong:
“however, even though the mp2 is only used as a battery charger while connected to the grid, ive been told that i still need g99.”
You don’t need an external contactor unless you set a grid code and want to feedback using ESS, and then depending on the firmware and inverter model you may also not need an external contactor.
You can use the generator start stop control and relay output from a GX to trigger ACin for timed charging.
Yes if you are not confident in doing it don’t, Victron is not a run of the mill setup so there are not too many people installing it, I was in the same boat, I just took my time done research and built it up slowly
As Victron states
1. Grid codes and complying to local regulations
All countries have their own legislation and therewith their own requirements with regards to the speed of Loss of mains detection, under & over voltages, accepted ramp times, and so forth. To make an installation comply to local regulations, the correct grid-code needs to be selected.
See guidance below on what is notifiable from one of the 14 DNO in the UK
Good morning,
Thanks for your email.
Any device being installed, even if the export is set to 0kW, must be registered as compliant on the ENA database so that they automatically shut off any potential export to the grid when there is a power outage (manual shut off will not be compliant).
If you are installing a battery to the DC side of an existing system and inverter, then you do not need to notify us as there is no change to the export that is already approved by the DNO. If the existing system does not already have an approval, then you will need to make the relevant application depending on the total export.
If there is no existing system / inverter and you are only installing a battery, then you will still need to notify us even if you are setting the battery to 0kW Export as the inverter for the battery will have the capability of exporting.
If the inverter for the battery does not exceed 3.68kW (the max. export capabilities will never exceed 3.68kW even if you set it to 0kW Export) then you will need to submit a G-98 Notification along with a SLD Schematic which can be done after installation. This will need to state the Export limit; if this is set to 0kW then you will need to accompany the application with a G-100 Declaration confirming the inverter will never export to the grid.
If the inverter for the battery exceeds 3.68kW, for example a 4 or 5kW inverter etc., then you will need to submit a G-99 application and SLD Schematic prior to the installation. As above this will need to be accompanied by a G-100 declaration if the Export will be limited to 0kW.
All forms can be found on the ENA website.
Regarding what we class as import when the battery is charging and if your supply is sufficient for the additional load, this will have to be investigated by an electrician who will calculate your usage including the device to be installed; we only assess the export onto the grid (any change in import will have to be discussed with an electrician and if your supply or main cut out fuse requires upgrading then you will need to come to us before hand).
Kind Regards
Logo, company name
Description automatically generated
Jason Haji
Technical Assessor
Phone: 020 3324 1460 ext. 5796
Email: Jason.Haji@ukpowernetworks.co.uk
Unit 5, York Way, Borehamwood, Hertfordshire, WD6 1DJ
Yes good info, I’m not trying to argue, and I’m not an qualified electrician, so feel free to ignore me and speak to a local Victron spark, but AFAIK… 
If you are not using ESS and the necessary LoM sensing etc, you don’t need to set the grid code for bi-directional use of the grid, this then locks the inverter out of being able to feed into the grid, that’s the whole safety point of not selecting a grid code, they can’t do it without it, and it’s only necessary if you want to use the grid for feed in.
The inverter is just a simple glorified battery charger and UPS. Of which there are many 1000’s of instances of UPS’s for personal essential load protection in UK homes without needing G99.
Boats and Motorhomes don’t call up UKPower Networks every time they plug in the charging cable in a new marina or campsite with no grid code set on the inverter, and nor would data centres with multiple simpler UPS/battery chargers which also do not feed back into the grid.
However, If the grid code is set, then yes it can feed in and yes it should have type ENA cert and G99 etc.
Maybe someone can correct me, but I assume the backfeed relay is permanently open, thus preventing backfeed when selecting no grid code - which is ‘non-compliant’ with the feed in rules for ESS functionality, but perfectly fine if you are not trying to use ESS and feed in.
https://www.victronenergy.com/live/ve.bus:grid-codes-and-loss-of-mains-detection
UPS are not sustained load ie I’m not seeing domestic UPS charging at 3.68kW to require G98 the comparison is not the same as a 4kW unit.
Compare it to a non directional car charger just 7.1kW has to have DNO approval before install or a Heat Pump
Granny chargers do not need it but the sustained 2-3kW has been know to burn out plug sockets 13amp sockets not designed for that sustained load.
The un-accounted load can affect the grid. This is what the DNO has to balance when making a decision.
The DNO is not just talking about feeding in they are taking about the load as well.
I think you’re still mixing up a system that needs to be compliant for critical LoM and backfeed suppression vs one that doesn’t.
With the analogies to justify why a DNO might need info on every load we apply for them to balance the grid, ignoring that an ASHP will happily go along @ 500W - 2000W most of the time. We have Economy 7 in the UK for people with resistive storage heaters, multi kW of loads in one house. We don’t need to contact the DNO when replacing an oil boiler for storage heaters, or when we get an electric shower, or every time we buy a fan heater, air fryer, tumble dryer, washing machine etc etc…
Most UK houses have either 60, 80 or 100A main fuses, the DNO don’t care what loads you have as long as they’re under the main fuse limit. Electrical safety is the reason for checking car charging, and the same for someone that wants to use a grid code and feed in, the risks to line workers are real if people ignore feed in rules.
If you’re not feeding in, and the inverter is set so it is not capable of feeding in (no grid code set) it’s just a load like all others in the house.
I think maybe that’s misinterpreting the regs for one thing and thinking it covers other different situations too.
I’m happy to be proven wrong by a qualified electrical engineer with access to the latest regs, but it just isn’t realistic, necessary, feasible or required for the tens of 1000’s of boats, campers and homes when feed in is disabled on their systems.
That’s not to say if you can, notify and get a Gxxx approval as it’s probably beneficial and future proofing in most situations.
1 Like
Apologies I should have just posted the whole thing instead of just the response. But this is my questions there answers
Good Morning,
I spoke to Connor this morning who said I should email in regards of connecting a home storage battery to the grid I am after a more definitive and formal answer to this question rather than what you say on your website.
There seems to be an assumption that if I have home storage batteries and connect them to the grid that
(1) As long as the inverter disconnects in a power cut the DNO does not need to be notified.
(2) As long as your not discharging power to the grid you don’t need to notify the DNO
(3) As long as you just charge the home storage batteries and then disconnect from the grid when fully charged, so no power goes back to the grid you don’t need to notify the grid (please clarify if there is any difference if this is done automatically by the inverter or by manual means if the answer is still the same)
(4) The inverter for battery storage is setup like an appliance ie just consuming power from the grid and not feeding it back that the DNO does not require to be notified.
(5) The device (Inverter)is registered on the ENA program and is not feeding the home storage batteries power back to the grid then the DNO does not need to be notified.
(6) The home storage battery is only 2.4kW load placed on the grid to charge (BUT IS NOT FEEDING THAT POWER BACK TO THE GRID) then the DNO does not need to be notified ( Please Clarify if 2.4kW load being placed on the grid requires DNO to be notified also please specify if there is a time frame for this load being pulled from the grid that would trigger the DNO to be informed ie the load is only for 30mins or an 1hour or so on)
(7) As question (6) but with a 4.8kW or 5kW homes storage battery that the DNO does not have to be notified as no power is being supplied to the grid, the grid connection is just for charging the home storage batteries.
I await your formal response to the above questions and appreciate that this would have to go through higher channels in order for a formal response.
Regards
Inquisitive Customer
UK POWER NETWORKS RESPONSE:
Good morning,
Thanks for your email.
Any device being installed, even if the export is set to 0kW, must be registered as compliant on the ENA database so that they automatically shut off any potential export to the grid when there is a power outage (manual shut off will not be compliant).
If you are installing a battery to the DC side of an existing system and inverter, then you do not need to notify us as there is no change to the export that is already approved by the DNO. If the existing system does not already have an approval, then you will need to make the relevant application depending on the total export.
If there is no existing system / inverter and you are only installing a battery, then you will still need to notify us even if you are setting the battery to 0kW Export as the inverter for the battery will have the capability of exporting.
If the inverter for the battery does not exceed 3.68kW (the max. export capabilities will never exceed 3.68kW even if you set it to 0kW Export) then you will need to submit a G-98 Notification along with a SLD Schematic which can be done after installation. This will need to state the Export limit; if this is set to 0kW then you will need to accompany the application with a G-100 Declaration confirming the inverter will never export to the grid.
If the inverter for the battery exceeds 3.68kW, for example a 4 or 5kW inverter etc., then you will need to submit a G-99 application and SLD Schematic prior to the installation. As above this will need to be accompanied by a G-100 declaration if the Export will be limited to 0kW.
All forms can be found on the ENA website.
Regarding what we class as import when the battery is charging and if your supply is sufficient for the additional load, this will have to be investigated by an electrician who will calculate your usage including the device to be installed; we only assess the export onto the grid (any change in import will have to be discussed with an electrician and if your supply or main cut out fuse requires upgrading then you will need to come to us before hand).
Kind Regards
Logo, company name
Description automatically generated
Jason Haji
Technical Assessor
Phone: 020 3324 1460 ext. 5796
Email: Jason.Haji@ukpowernetworks.co.uk
Unit 5, York Way, Borehamwood, Hertfordshire, WD6 1DJ
http://www.ukpowernetworks.co.uk/
Title: LinkedIn - Description: image of LinkedIn icon Title: Facebook - Description: image of Facebook icon Title: Twitter - Description: image of Twitter icon
My manager is always looking for examples of good customer service that can be shared with the team. If you are happy with the service you have received, I would be very grateful if you could email me with your comments so that I can pass them on to management.