Warning notice Borrowed neutral on lighting circuit

[olsonn]

Doing a CU change, but have already spotted that there is a borrowed neutral between the two lighting circuits with both being fed by the same MCB. The job is in a flat and there is only a single light in the entrance hall on one of the circuits. The customer wants a straightforward swop and doesnt want to pay for any additional work. I have a couple of questions that hopefully somebody can help me with.

1. I assume that I can leave the 2 circuits being feed from the one MCB on the new board. It is a split board so if I try and seperate the circuits across the 2 RCD's obviously I would have tripping problems.

2. Can I put the neutrals of each circuit together on the board and the CPCs together or should I keep them seperate?

3. I know I will need to put a warning notice on the CU to highlight the borrowed neutral. Is there a specific wording I need to use or sticker that I could buy, or is it a DIY job?

 

[johnboy6083]

IMO, no sticker required., now that both are on the same MCB, and there is only one fitting( that was originally on another cct), the circuit is wired in a similar way to how conduit sytems are wired, wher a neutral will be taken from the nearest point, and the switchlve from another. You may decide to note it on the EIC, but uits upto you.

 

[scotsparky]

How can it be a borrowed neutral if its on the same mcb?

Its a non standard circuit. They have taken the supply to the hall light from the mcb double check all other neutrals you may find it there which will give you multiple circuits on the same MCB.

 

[scotsparky]

beaten by johnboy

 

[johnboy6083]

to go by the book, is a circuit not defined as electrical cables supplying electrical equipment, fed from the same protective device?

 

[Specialist]

Don't see where you have a borrowed Neutral, you've got a lighting circuit & from the sounds of it someone has added an extra light in the hallway. Instead of takeing the feed from another light it may have been easier to take it from the CU. Just put Lives together in same breaker, Neutrals together in same terminal on Neutral bar & same on the Earth bar. No need for a Label. Pretty common way of people adding lights in Flats.

 

[telectrix]

agree. if fed from same breaker, it's only 1 circuit.

 

[olsonn]

There is a 2 gang switch in the entrance hall. one switch operates the entrance hall light and the other operates the upstairs landing light The landing light also has its own switch upstairs. when I tried to split the 2 lighting circuits across the 2 RCDs and operated the landing light using the downstairs switch both RCDs tripped. This is why I think there is a borrowed neutral in the upstairs landing light.

 

[oldAL]

its a funny flat with stairs in!
but, as has been said, keep them on one MCB and then its only one circuit, so no borrowed neutral.

 

[mogga]

its a funny flat with stairs in!
but, as has been said, keep them on one MCB and then its only one circuit, so no borrowed neutral.

Lots of flats have stairs in them You need to get around a bit more

 

[telectrix]

it's bungalows that don't have stairs (usually)

 

[sparky3366]

unless its a dormer bungalow...

 

[martinxxxxxx]

Doing a CU change, but have already spotted that there is a borrowed neutral between the two lighting circuits with both being fed by the same MCB. The job is in a flat and there is only a single light in the entrance hall on one of the circuits. The customer wants a straightforward swop and doesnt want to pay for any additional work. I have a couple of questions that hopefully somebody can help me with.

1. I assume that I can leave the 2 circuits being feed from the one MCB on the new board. It is a split board so if I try and seperate the circuits across the 2 RCD's obviously I would have tripping problems.

2. Can I put the neutrals of each circuit together on the board and the CPCs together or should I keep them seperate?

3. I know I will need to put a warning notice on the CU to highlight the borrowed neutral. Is there a specific wording I need to use or sticker that I could buy, or is it a DIY job?

It is not really a borrowed neutral - it is a stolen live.

Look at 314.1 which is the rule that gave birth to the dreaded "17th Edition " boards. What you are proposing is a bodge and breaks this regulation, so you will need to note it a departure on the cert.

 

[markc123]

I would hope the OP had already completed the CU change martinxxxxxx lol.

 

[martinxxxxxx]

There is a 2 gang switch in the entrance hall. one switch operates the entrance hall light and the other operates the upstairs landing light The landing light also has its own switch upstairs. when I tried to split the 2 lighting circuits across the 2 RCDs and operated the landing light using the downstairs switch both RCDs tripped. This is why I think there is a borrowed neutral in the upstairs landing light.

You mean that the downstairs circuit is providing the live feed for the upstairs light. All you need to do is to re arrange things so that the upstairs light is getting its live feed to the switch from the ceiling rose of the upstairs light, at the moment it is getting it via the 2-way circuit from the downstairs light ceiling rose. it is just one piece of wire that is needed to make things right. That would save you having to note a departure and make it a lot safer.