I don’t think it says what you think. The earth connection says the following:
‘’‘Earth/ground busbar for both AC input PE, AC output PE and chassis earth/ground M6 connections.’‘’
They are all connected together with no relay on the earth path, except to connect to neutral.
It all stated in the regulation 551.4.3.21 of BS 7671 that the distributors earthing arrangement cannot be relied upon in island mode and the consumer’s own arrangement must be used. The PE relay will be open when grid parallel and closed when in island mode as the you also only allowed one referencing point. It goes on further to say both the supply side and consumer side earth electrodes can be connected at the same time in islanding mode.
DNO’s can ultimately decide whether they will allow export based on based on Ofgem guidance paragraph “1.14 Making SEG payments is ultimately at the discretion of a SEG licensee, were you unable to demonstrate your system is appropriately certified or they accept alternate forms of evidence of compliance”. HOWEVER, SEG licencees will typically strictly adhere to the guidance very much leaving you at a dead-end and demand MCS certificates. Octopus will require the DNO’s G98/G99 approval letter for your installation and a building regulations certificate of compliance. The latter you will be able to obtain if you have an EIC (electrical installation certificate) given new circuits can only be installed and Part P notified by qualified electricians. Without this, you may be going nowhere. You may also be able to have the local building inspector sign off your installation, but I do not have insights on applications following this route.
@ejrossouw
Thanks for both of your responses, got an electrician who will do the work, but it’s been a journey as people have said they will do it and then struggle as they lose confidence in their abilities. It’s been a bit disappointing tbh…
Do you have a copy of the BS 7671 paragraph 551.4.3.21 you mention, as I keep being told a local site earth electrode cannot be connected into the grid earth. Seems totally bonkers given gas/water pipes are effectively this, but one electrician, one MCS and a UKPN person have all told me this… Keeping the grid earth would be great since no amount of trying will give me an earth rod that is as good…
Just to be clear, for islanding you cannot rely on the supply earth only and need bot in place. May be a non starter. Electricains should have access to the regulations as I cannot post copyright material.
Sorry, I know I would need both, but when not in island mode (99.9% of the time probably) it would be better to use the grid earth, assuming you can connect them together - which is definitely not what I’ve been told. The difficulty is in separating them to use one in connected mode and one in island mode.
Any spark should have assess to the regs book which @ejrossouw has referenced so ultimately they can satisfy themselves but a lot boils down to plug and play systems which Victron isn’t, it’s more versatile but ultimately more complex because of that and I think here lays the problem with an every day spark not familiar with whole house backup and flexibility of the platform. Took awhile for me to design my with a lot of help from people on here.
I think if you have a system diagram which you should have already due to DNO app, it should be a lot easier for the spark to follow only issues really is programming which I guess a lot of sparks will be lost on.
This is who I was talking to that said they could be both connected, but I’m happier to run TT seen as I’m TNC-S I’ve heard of a lot of broken neutrals so I’d rather have no power than the power going through pipes due to the earth reference of the metal pipes. But see video to your earthing which @ejrossouw has mentioned
Thanks again both of you, I’ve now watched and read a bit more and I feel confident ensuring an electrician does the right thing, but it does seem as though many I have spoken to do not know!
I have an MP2 5000/70 2022 in line whose input is off a Sub main from the meter through an RCD on 16mm2 SWA. Main fuse is 80A. Distance about 8 metres to an outdoor cupboard hosting Pylontech 10.5kWh. And 3.8kWp.
Output goes back along an another sub main to the household CU. While system runs of MPlusII which is great when the community power goes off and nothing changes. Happened four times last year.(UK)
Household earth and islanding earth both connected via rods.
4.5kW plenty for the small house. Grid assist happened once when a carpet cleaner used 2 x 13a sockets for 7.5kW just after installation.
I have a 100A-4 pole changeover switch, switching MP2 inputs and outputs to “put it all back to normal” so the inverter can be isolated taken offline for any reason.
After going to South Africa and seeing a 3 position c/o switch on the CU DIN rail that said simply, CU to Generator, CU to grid and mid position isolated, made me think I might have gone too far with the big c/o switch and I could simplify my design.
I had the system commissioned to get the DNO and MCS approval. Paid £300 and the dno came out and tested/timed the 22 second? Inverter-grid disconnect when grid was off. My sparks connected up the business ends for me but I did the cable runs and cabinets mounting. ElectEng myself.
My TT earths are permanent wired under the house and next to the outbuilding.
I will challenge the DNO as documentation clearly shows an island setup that is not disconnected from supply earth. What is important to note is that the TNC-S earth reference is lost with ACIN being disconnect in island mode. A new reference is established by connecting N to E and this ensure RCDs will operate correctly.
I think the complexity with tncs is if you do not do a whole house backup, since then there will be grid neutral in some places in the house and an isolated neutral from the inverter in others. But this is probably minor, though not sure about regulations, at least the earth will be good, and perhaps even a good reason for tying together TT earth with grid earth since then it removes the neutral risk…
The IET code of practice recommends having a local earth rod alongside the DNO PME.
See figure 3 a & b
I got very involved in this but have forgotten most of it. I’ve ended up with seperate earth rods to all my consumer units and the victron with the PME remaining connected. The PME dissappears when the grid goes as it both uses the neutral and then splits the earth off the neutral when it gets to the cutout.
My problem was when I switched back I got some of the RCDs going as it had different earth resistances. We nver fully fixed it I fixed one building by ditching the RCD and a circuit in th house by binning RCD. It may even have been high earth leakage as electronic capacitors recharged on reconnection..
Possible solved by time delay RCD to create select-ability, but would have been better to combined or use just the rods, I’ve got a time delay upfront of 100mA’s as I want the RCBO’s to trip circuits rather than the whole house
Selectivity!
lol yes selectivity lol
