2 x 10mm in Isolator.

[skatingsparks]

Morning
I did a job for a client and, as usual, did it to the best of my ability/knowledge. The client told me the AIA inspector would be going to have a look which I was more than happy for them to do. It was a big project and the client has been screwed by a few other electrcians and it was also a fair sum of money (block of flats).

So bet the client a 4 pack of Leffe blond beer that the inspector would find nothing more than labels and cosmetic things (client wanted cheap but compliant)

Other than labeling all was good on the AIA inspectors report (usual really picky things - but they really had to dig for them)

Only thing I had a issue with was:- '

I have an 80amp 3 phase breaker supplying boards via 25mm GP with 16mm c.p.c. run in existing metal conduit in risers to individual boards on each floor of the block. In the riser board I have a 100 amp 4 pole isolator. The boards (there are 5 floors - 1 x 80 amp 3 phase circuit for each) feed 5 flats (one floor has 6) per floor. Each flat has its own 50 amp single phase breaker covering the flat DB. I spread the flats over the 3 phases alternating over the floors. So on 1st floor - red has 2 flats, yellow had 2 and blue had 1 then the next floor, red had 1, yellow had 2, blue had 2 etc...).

1 have a 2 x 10mm Gp cable coming from the bottom of the isolator feeding 2 breakers (or 1 if its the phase for that floor to only have one flat).

I also have 2 x 10mm neutrals coming out of the 4th pole of the isolator to feed to neutral bars (1st 2nd and 3rd flat on one bar 4th and 5th on the second bar.

The AIA picked up on just the neutral coming out of the isolator. No mention/problem with 2 x 10mm GP's to supply individual breakers - just the neutrals

My line of thought was you will never get more than 50 amps through either neutral (3 x 50 amps = 50 amps in neutral).

It was picked up because :- 'Neutral connections inadequate - conductor of cross sectional area exceeding 4 mm not to be install to allow conductor to be disconnected without disturbing the disconnection of any other neutral conductor.'

I know that applies to neutral bars in DB boards - up to 3 cable less than 4mm in a neutral bar etc (if someone could find that reg number because I have been looking for about half hour now)

If its the same circuit - the supply to the board - why would you try remove a neutral?

I don't like putting 2 or 3 cables in a terminal in a neutral bar but does this regulation apply to the isolator. I pretty sure its ok to have 2 neutral going into an isolator/breaker (parallel supply) so why not out?

I could understand if i had jammed all the neutrals from the flat suply in there. But the isolator can easily take a 25mm cable.

Sorry for the bad pic. but it was snipped of the report.

Any one see a problem with what I have done?



P.S. would have like to have put bus bar system in but space was limited. Thats the biggest board I could get in teh cupboard