beware the borrowed neutrals & 17th edition consumer uni

[tjsparks]

A tip for everyone beware when fitting these new dual rcd boards and separating upstairs and downstairs lighting on different rcd`s .If the rcd trips good chance caused by a borrowed neutral on the the landing may save you all a bit of time looking.
Had two of these now in council type properties.If customer doesnt want to pay for a new neutral running in AND I know ITS NOT GOOD PRACTICE BUT put upstairs lights and downstairs on same rcd and problem solved.

 

[Lectrician]

It was common to to borrow a live (not the neutral) for the landing light from the downstairs hall light switch. (two core strapper to landing).

When ever I have seen this, the upstairs and downstairs lighting circuits have been in the same fuseway - a typical 4 way 3036.

The times I have seen it split is when there has been a CU replacement, and someone has seen fit to split the cables because they hate seeing two cables in an MCB.......

 

[Spark123]

Not a problem solved, a problem botched and left for someone else to get a shock with.

 

[tjsparks]

Not a problem solved, a problem botched and left for someone else to get a shock with.

GOD WISHED I WAS AS GOOD AS YOU

 

[holmslaw]

..

 

[RF Lighting]

Now this is a rare occourence, but for once, I have to agree with holmslaw.

What you have done is gross neglegence, and you deserve to be sacked for doing it.

I could understand if you were incompetant, and had done it in error, but to come on here and BOAST about it???

There is no need to try and get clever with Spark123. It's not about being 'good', it's about leaving electrical installations in a safe condition.

Did you complete an electrical installation certificate for the works to BS7671:2008? If so, you have also commited fraud.

 

[Lectrician]

If he had said "place them in the same MCB" I would be happy(er).

Saying "place them on the same RCD" is circa to saying "Put them on the incomming side of the main switch - it works then".

A borrowed neutral is there waiting to get some poor sod.

Seen it happen as an apprentice.

Not a death, but a fall from scaffolding when a spark was working on a row of flourescents in a warehouse we were subbying at.

 

[Spark123]

I got one with a conduit system where someone had picked up the wrong neutral upstream - the fitting tested dead until I parted the neutrals!

 

[garethg]

Would someone mind posting a circuit diagram of the before?

I am finding it difficult to think of a situation where the neutral doesn't run close to the live it is meant to be with.

 

[Lectrician]

Best I can do when in a rush......

Brown and Blue is obvoiusly far more likely to be red and black!

This arrangement is fine if you had both circuits in the same MCB/Fuse, but preferably would form a single circuit, with one cable presented at the CU.

There is a single core red or brown double insulated used between landing switch and landing pendent.

 

[we8albion]

tjsparks i am disgusted with you as well because you are giving us cowboys a bad name!
As a fully competant part p (pasteurised) registered milkman I often do the odd job so we dont need cowboys like you on this site.

POWER TO THE COWBOYS.

THE COWBOYS WILL NEVER DIE

WE`LL KEEP THE GOLD FLAG FLYING HIGH

WHEN I GROW UP I WANT TO BE A PROPER LECTRICIAN AND NOT A COWBOY!!

 

[sm1thson]

I am not a spark but i can tell you tjsparks this was equally wrong on the 16th as it is the 17th.

I found my house has a borrowed live (or neutral depending how you look at it) on my landing lights, thankfully i found it before it found me or i may not be writing this, I knew it was wrong back then (before the 17th) I cant believe you think its acceptable under the 17th (with the provision of the RCD added) its not!

borrowed neutrals are one of the worse faults in my opinion as they are not obvious to spot: you can turn a circuit off, test it is dead, disconnect the wire and at that point it becomes live and bites you!

 

[jason1958]

This was very common with 2-core (flat-twin) and 2-way hall switching

There is one improvement...
- Fuse-A has 2 runs of 2-core
- Fuse-B has 1 run of 2-core

Fuse-A 2 runs of 2-core are so one provides a dedicated live feed.
- 1 run for upstairs lighting - and neutral of upstairs & hall
- 1 run for hall & porch lighting - and neutral for porch

Fuse-B 1 run of 2-core in one fuse were used for downstairs.
- 1 run for downstairs lighting

The downstairs hall had the hall 2-way & porch switches.
- Porch drop = L-Supply to both Hall & Porch + L-Sw for Porch
---- Neutral for Porch in Jn-Box under landing off 1 run of the 2-core
- Hall drop = L1-Sw L2-Sw for Hall
---- Neutral for Hall in Jn-Box in loft off 1 (other) run of the 2-core

If you looked at the *switches* it looks like a borrowed live.
It you look at the *CU* you would find 3 lighting cables.

 

[jason1958]

Oh, to the OP...
- You should put the lighting back on 1 MCB
- At least it will then not bite someone - or kill them
- If necessary stick an EmLight in the hallway

Some solutions.
1. Replace hall cable with 3C+E

Provide proper 2-way switching with L/N off 1 circuit only.
So permitting separate Up & Down lighting circuit RCBO/RCD.

2. Replace hall borrowed L/N with 6181Y off 1 circuit

6181Y does go down to 1.5mm, very small, discrete.
If necessary use smallest D-Line or razor the paper, slip in (very hard).
So permitting separate Up & Down lighting circuit RCBO/RCD.

3. Run hall lighting off SFCU off a power circuit

So permitting separate Up & Down lighting circuit RCBO/RCD.
Also effectively putting hall lights on a non-lighting circuit, so a hall light blowing does not take out an entire floor - both floor level lights are left to cast light into the hall. EmLight may still be a good idea obviously.


A relatives lights are 3 cables, 2 on one RCBO, 1 on another.
However telephoning now she says 1 RCBO can be on/off yet all the lights including hall work. So I need to investigate what has been done there. I suspect it is as per my previous post, but someone stuck a cable in the one wrong RCBO - will need to trace carefully next time I am there.