Multi-core neutrals and earth

[Deleted member 26818]

Definitely needs a KISS.

 

[FatAlan]

Definitely needs a KISS.

Great principle to adhere to. Also, never assume as it tends to make an ‘---’ out of ‘u’ and ‘me’
A bit like an expert .... an ex being a has-been and a spe(i)rt being a drip under pressure!

 

[davesparks]

It is more of a parallel conductor design than being a shared neutral in my opinion. The person I am working for is electrically qualified and this is how he said we wire it. I am unsure that is the reason I am asking here.

In this configuration it is impossible to get a dangerous voltage on the neutral so long as the neutral is terminated in the consumer unit, same as any circuit. It is not like a situation when you borrow a neutral from a different lighting circuit. It is not a dangerous configuration.

It is not a parallel conductor design, that would be a single circuit spread over multiple conductors.
The regulations prohibit the use of a shared neutral conductor in the manner you are suggesting.
It is dangerous, if someone was to isolate one of these supplies and disconnect the neutral at any point in the circuit where it may not be obvious what you have done the disconnected neutral will become live.
Any EICR carried out in the future will identify this as potentially dangerous and you could have a very angry customer coming back to you, taking legal action against you or generally ruining any good reputation you may have.

This plan is also a bad idea from a common sense point of view, any person working on the circuit in the future may need to isolate up to 5 circuits to carry out work on one of them safely . So you end up with a situation where you have to isolate an alarm and two gates to repair or extend an apparently unrelated lighting circuit.

 

[Gigsy]

I know I’m only a trainee but that design does look over complicated. DB at each location and 3 core SWA calculated on max demand and distance.

It is over complicated, I would design it different, but the person who's house it is wants all the breakers in one location.

 

[Gigsy]

It is not a parallel conductor design, that would be a single circuit spread over multiple conductors.
The regulations prohibit the use of a shared neutral conductor in the manner you are suggesting.
It is dangerous, if someone was to isolate one of these supplies and disconnect the neutral at any point in the circuit where it may not be obvious what you have done the disconnected neutral will become live.
Any EICR carried out in the future will identify this as potentially dangerous and you could have a very angry customer coming back to you, taking legal action against you or generally ruining any good reputation you may have.

This plan is also a bad idea from a common sense point of view, any person working on the circuit in the future may need to isolate up to 5 circuits to carry out work on one of them safely . So you end up with a situation where you have to isolate an alarm and two gates to repair or extend an apparently unrelated lighting circuit.

Good point, thank you. Glad I checked with the forum.

Do you know what reg, forbids shared neutrals?

 

[Gigsy]

I just drew this. Not sure if it makes sense or even it is correct. Any feedback would be welcome.

 

[ruston]

[QUOTE="Gigsy, post: 1502649, member: 97625.

Do you know what reg, forbids shared neutrals?[/QUOTE]

Have a look in the index of BS 7671. That will lead you to 314.4

 

[Gigsy]

I found the regulation in BS7671

314.4, yellow book

When an installation comprises more than one final circuit, each final circuit shall be connected to a separate way in the distribution board. The wiring of each final circuit shall be electrically separate from that of every other circuit, so as to prevent the indirect energizing of a final circuit intended to be isolated.

 

[Gigsy]

[QUOTE="Gigsy, post: 1502649, member: 97625.

Do you know what reg, forbids shared neutrals?

Have a look in the index of BS 7671. That will lead you to 314.4[/QUOTE]

Thank you

 

[ruston]

@Gigsy . Nice to see manners. It is a pleasure.

 

[FatAlan]

You’d still have one MCB at the house DB for each out building and as others have said, have your RCD’s at small DB’s at each out building for the individual circuits. Does your client have a particular reason for their design other than wanting to have s massive consumer unit at the house?