Shared Neutral?

[steviec_lj]

I need to put further provisions in for welders in the workshop, so I've an idea of putting a 32a and 16a connector in a box in opposite corners, so I'm covered wherever I need to weld without the added hazard of excessive extension cables all over.

I split the circuits in the workshop across two RCD protected boards, mainly due to the number of circuits, but it also leaves one bank of lights on should I trip an RCD. Now, these boxes will be off a different distro for the same reason.

Question is, can I share a neutral and earth in the boxes to save pulling three 6mm2 and three 2.5mm2 singles through a conduit run? Both connectors will be on separate MCB's.

Its also tempting to drop a double 13a under these boxes too, daisy-chained from the 16 or 32.

 

[rtbcomp]

A diagram would help.

Personally I'd keep lives and neutrals together, especially where RCDs are involved as the live and neutral currents must be the same to avoid tripping.

 

[brightspark]

A diagram would help.

Personally I'd keep lives and neutrals together, especially where RCDs are involved as the live and neutral currents must be the same to avoid tripping.

as said u dont have any choice /the live and neutral must come out of the same rcd for a balanced load .u can not just share a neutral with another rcd as it would inbalance the load and both would trip out

 

[sparkysy]

I would have to agree with brightspark! borrowing neutrals is a big no no in my book too! If you turn one circuit off there is still a major shock risk from the neutral if equipment is being used by the other circuit! My rule of thumb is do it once properly and sleep sound at night!

 

[ford34/2]

I`m not a sparky but my sons Kitchen cabinet unit down lights were wired by a blind and incompetent electrician, replacing the kitchen units when he moved in, I thought I had done it all neat and tidy but i picked a stray neutral up off a 13 amp socket under the cabinets, seemed ok till I turned the mains back on. I was goona say earlier , but I hate trying to give advice on things I am not qualified or competent to do,
It got done right in the end with a new supply back to the Consumer unit .
Another set were spured off the cooker supply isolator, think the supply was on an MCB about 30 amp. could even have been 40?
3rd set was off the ring main!!!!!!!!!!!!!!!!!
and you wonder how they remain live when the light circuit is dead!!
Stan

 

[steviec_lj]

Picture of box attached.

Would like to come out of one distro to this. Will two lives, a neutral and earth suffice, or do I need to pull a live, neutral and earth in for each socket? The entire board for this "box" is covered by an 80a RCD.

 

[Screwdriver]

Sounds well dodgy to me. You really ought to follow code because if you forget what you've done or someone else comes along, you could easily end up with a live wire being fed to a junction box which appears to have been disconnected.

If you're doing it just to maintain a lighting circuit in the event of a trip, perhaps you'd be better off addressing that issue separately. Battery backed lighting or an isolated lighting circuit.

S.

 

[sparkysy]

Mm that is a doozy in theory you could run 1 32a 6mm say supply to the whole box as the wiring and 32a outlet are protected by the mcb and the appliances in the socket would have 13a fuses in but that would leave the 16a outlet dangerously unprotected?! Or you could run 2 supplies one 32a for the top outlet and one 16a for the other and twin socket, or again you could run 3 seperate circuits for it so they are all individual. Depends on if it's just you using the outlet as this would limit the load drawn

 

[Robotstar5]

Picture of box attached.

Would like to come out of one distro to this. Will two lives, a neutral and earth suffice, or do I need to pull a live, neutral and earth in for each socket? The entire board for this "box" is covered by an 80a RCD.

Don't forget the neutral and earth wires must be capable of carrying current/fault current of both sockets.

 

[dobbslc]

As has been said above really, you should run a seperatly 16amp feed for the 16amp socket and double socket outlet and a 32amp supply for the 32amp socket using the correct sized cables.
Don't borrow / share neutrals as it can kill you or someone else at a later date!
Just run two circuits with their own neutrals and earth and DON'T get the neutrals mixed up, mark them seperatly and tape them to their corresponding lives.
If it's fed from a 3 phase board on two different phases make sure it's all marked up as having 400 volts in the conduit and boxes.
Sleep easy.

 

[steviec_lj]

Only me using the system. Just trying to cut a corner and save on dragging cable in, especially as all neutrals and earths are back to the same point.

Have looked at trying to fit a 16a breaker into the box so that it can all be from one 6mm feed, negating the issue around shared neutrals or unprotected outlets. Shall study some more, it looks possible..

 

[brightspark]

well if u have a 6mm cable feeding it why dont u just fit a 2 way db .wire down in to the 30 amp socket of one 32 amp mcb then fit a 16 amp mcb wire down to a 16 amp socket and loop a feed out of it to the 13 amp socket its hardly likely u will use them all at same time

 

[steviec_lj]

Doing the job with what I've got lying spare in all these storage boxes. If I didn't have it spare, it would end up not being done and I'd just drag 15mtr extension cables around.

Managed to squeeze a 16a breaker in, and could probably get another in too. Not pretty, but serves a purpose.

 

[brightspark]

have u just done all that in the last 3 hours cos thats when u posted for advice

 

[steviec_lj]

Yup. 3 hours ago I thought of the idea whilst filling my face with tuna pasta.

Getting tired of dragging long cables around, then tripping over them. 2 weeks of quiet/slow work at the moment while stuff gets painted and shipped back to me, so now is the time to make the workshop work rather than "just making do".