Lighting and the dreaded borrowed neutrals !!!

[tuckermot]

Hi all

In the board changes i have done i have never come across a borrowed neutral on a lighting circuit,how common is this and between what years was this practice done .

Richard

 

[tony mc]

It was just a post with different opinions re placing either in seperate mcb;s or placed into one mcb.

 

[ezzzekiel]

a single core will be in the upstairs light (switched live) disconect all the cables and put in junction box above ceiling except the single core which is your live from downstairs, run a twin earth from downstairs lighting or fusebox upto the light (cut back the live as its not required) you will end up with a switch live and new neutral and earth at the upstairs lighting point.

 

[telectrix]

i prefer to remove the live feed from the downstairs and run 3 core between the switches , if practicable, bearing in mind the damage to decor. obviously, each job would need it's own assessment of the best way to go with minimal disruption to decoration etc.

 

[steve447]

The last one i saw took me a while to suss it out, but with the help from this place i got it sorted, by as mentioned above running T&E from a JB on the downstairs lighting to the landing light and putting the rest in a JB in the loft. However it was whilst doing this i realised there was one too many wires in the loop in of the ceiling rose, a bit of head scratching and then getting the meter out confirmed that whoever done this had dropped the switched live down to the switch (using the black cable, no sleeving in sight) but had also connected a red to the loop in but just left it cut back (live at the switch). The switches were out of the bloody ark and once i got the switch plate off and found there was no back box but only a lump of wood which the switch plate was screwed into and the the live from the ceiling rose loop had made a nice scorch mark and was a rather burnt black colour at the end. Must of been that way for over 30yrs according the owners.

 

[Chr!s]

I usually shove them on the same RCD but into separate MCB's, at least if they pop a lamp it normally takes the MCB out just for that circuit and doesn't plunge them into total darkness.

Id be a little concerned about seperate mcb's, makes more sense if loading permits to make one radial circuit.

Chris

 

[BlueToBits]

clues that may indicate a borrowed neutral on the landing light:
Landing light works when fuse on the upstairs light is pulled
link wire bridging the 2 gangs of the hall light switch.
neither of these will categorically prove there is a borrowed neutral without measuring continuity L-N on the downstairs circuit with the landing light on and off. Different readings should be seen if there is a borrowed neutral - a good GLS lamp must be in the landing light.

 

[BES]

I'd always prefer to fix the problem using a single neutral and earth (6241Y) from the downstairs circuit. I have fitted a RCBO before and noted on the certificate but i still don't like the idea that one fault will take out all the lights, just doesn't seem safe to me.

Do exactly the same as dunc.:yesnod:

 

[NICK C SPARKS]

if problem cant be found due to tiled or lam flooring got to place on 1 mcb protected by rcd tie rap all cables on that circuit so cant be seperated if accross 2 mcbs say some body decides to put a new fitting up turns off the light circuit in question tests and is dead then somebody turns a light switch on that is protected by the other mcb there is a good chance the person fitting the light is going to get a shock thats my take on it unlikely to ever happen but could