Inverter diagram for one phase on 3 phase installation feeding 2 db’s

[Pieter00]

Hi guys, so when doing an inverter installation where the main db on ground floor is 3 phase as well as the dB on the 1st floor is 3 phase, how would you go about separating the circuits especially working with the neutral when the inverter must work on one of the phases only for example the blue phase and it must feed a couple plugs and lights downstairs and upstairs? Would you pull a separate cable for the upstairs dB and have it connected on the output side of the inverter? Sans only has diagrams for single phase installations and I’d like to get your views on this. What happens when you don’t run a separate cable for the couple circuits for the upstairs db that must be on the inverter and what happens with the Neutral? My thinking with pulling another 2 core + earth for the couple circuits would then be to put it in its own little db next to the upstairs db making it easily identifiable as to what circuits are on feeding via the inverter with the circuits in the downstairs db.
What is your take on circuits in a db board running through alternative power and it being clearly identifiable? Would you rather put it in its own little db next to the existing db or keep it in the existing db and just label it properly? Finding the neutrals in an existing db is a nightmare

[GCE]

Hi
If you don't separate the neutrals you can end up with weird and wonderful intermittent problems with the inverter circuits and being 3 phase even worse.

If it was me , I would put a separate DB downstairs and run a cable upstairs to a separate DB - If the existing DB's have sufficient space that you can maybe arrange everything on one rail along with a separate neutral bar , then that could also work.

[Pieter00]

I tend to agree but in another 3phase installation the same neutral is used for a couple circuits for bottom and upstairs db and it worked perfect with the inverter. I had a chat with the ECB technical director yesterday also and he said till the regulations regarding solar is finalized, all the neutrals must have 1 common point. Sounded like this inverter and pv stuff is like opening a can of worms

[GCE]

Hi

I disagree with the technical director of ECB and welcome him to show me in the reg's where it is stated that all neutrals must be common.

The present code SANS 10142 ed2 and what i see on the Draft ED 3, which is now out but I am yet to receive my hard copy ,shows the neutrals to be split.

The neutrals on the output of the inverter need to be on a separate neutral bar according to Annex P .

I would be interested to hear back as to how he arrived at his statement.

[SeanM]

Morning All

I agree 100% with GCE and the annexure has always been like this in the last edition and the new one.

I have just purchased the 2020 version of SANS 10142