Lighting Circuit - Neutral Arcing

dubliner24

Hi guys,

Was fitting a new lighting rose in one of the bedrooms in my brothers house recently. I identified the MCB and switched it off.

Strangely, the landing light stayed on - is this the norm? I would've thought it'd be on the same circuit as the rest of the upstairs lights?

Anyway - when I removed the wiring from the old rose (having checked that the live wires were dead!) I noticed arcing across the neutrals... and the landing light flickering.

I'm assuming the live for the landing light comes from another circuit, but the neutral ties into the bedroom circuit?

Taking a voltage across neutral-earth I got 1-2 volts.

Can anyone shed some light on this? pun was just too good not to use.

(as an aside - the house had a large extension built on before my brother moved in, the wiring in the attic is a mess)

mikeyjames9

dubliner24 wrote: »

Hi guys,

Was fitting a new lighting rose in one of the bedrooms in my brothers house recently. I identified the MCB and switched it off.

Strangely, the landing light stayed on - is this the norm? I would've thought it'd be on the same circuit as the rest of the upstairs lights?

Anyway - when I removed the wiring from the old rose (having checked that the live wires were dead!) I noticed arcing across the neutrals... and the landing light flickering.

I'm assuming the live for the landing light comes from another circuit, but the neutral ties into the bedroom circuit?

Taking a voltage across neutral-earth I got 1-2 volts.

Can anyone shed some light on this? pun was just too good not to use.

(as an aside - the house had a large extension built on before my brother moved in, the wiring in the attic is a mess)

Yes the landing light has borrowed a neutral from the upstairs circuit you had switched off

Its not safe for the reasons you described and for testing purposes each circuit should be separate

I doubt anybody is doing it now, not RECS anyhow

mikeyjames9

There's a regulation covering attic wiring now, et101:2008

The cables must be laid in an orderly fashion and not zigzagged everywhere

dubliner24

Thanks mikeyjames - I thought as much but was wondering if I was correct. Was that the norm in days gone by?
Is it OK to leave it as is?

I had a feeling the folks that did the work on the extension were cowboys!


I just got new copy of ET101, I must look out for the details on attic wiring.

mikeyjames9

dubliner24 wrote: »

Thanks mikeyjames - I thought as much but was wondering if I was correct. Was that the norm in days gone by?
Is it OK to leave it as is?

I had a feeling the folks that did the work on the extension were cowboys!


I just got new copy of ET101, I must look out for the details on attic wiring.

It was commonly done many years ago

Just one of those things, hopefully you wouldn't see it now

deandean

what you probably have is 2-way switching on the landing light. switch & light downstairs. switch & light upstairs. which neutral to use aaarrgh!

2011

deandean wrote: »

what you probably have is 2-way switching on the landing light. switch & light downstairs. switch & light upstairs. which neutral to use aaarrgh!

It is clear wich neutral to use. Each circuit should have its own neutral back to the distribution board. "Sharing" a neutral with another circuit is not permitted. This can cause a neutral to be overloaded. Don't forget that a neutral used in this way may not have sufficient over current protection as generally a protective device is only fitted to the phase conductors (not an issue when wired correctly).

adrian92

With lighting circuits safest to do in daytime. Isolate the lot! The voltage you measured was probably just an induced voltage.

dubliner24

Cheers adrian92. Good tip to just do it during the day and isolate the whole lot!

When you say an induced voltage.. what would be causing that?