Switched Neutral Fault Finding

[DyFamCont]

Evening all,

I had a quick Friday afternoon domestic job that has turned into a PITA and I'd appreciate your help.

While adding some new lights to a circuit, I found that the switch where I was taking the additional line from was actually switching the neutral. After much swearing I checked the polarity at the ceiling rose and got some odd results from the ceiling rose as per the table below. The part that's confusing me is why N-E is at 230v with the switch open.

Being a domestic job, I can't follow the cables properly without wrecking the place but have done continuity to find out what each goes to. The camera in the ceiling revealed nothing of significance. I'm assuming there's a junction box somewhere in the middle where someone has messed it up. The rest of the lights in the circuit have the correct polarity.

Any help would be greatly appreciated because I said I'd go back tomorrow.

 

[westward10]

Your live readings at the rose are they at the loop in, assuming there is one.

 

[DyFamCont]

Your live readings at the rose are they at the loop in, assuming there is one.

Thanks for your interest.

There isn't a loop at the ceiling or switch, so I assume its in a box in the ceiling. I can't access it though, so just assuming

 

[plugsandsparks]

Have you tried it without the lamp in the holder ?

 

[Eric12]

sure im not going mad but them readings are as they would be if the neutral is switched, so looks like you need to extend the feed so the line an be switched, and put a blank plate on the existing switch !

 

[Eric12]

The part that's confusing me is why N-E is at 230v with the switch open.

As the switch is breaking the neutral (causing open circuit) then the neutral will show potential to earth. The neutral is a live (potential to earth) conductor isnt it if its not going anywhere

 

[OLDBOY]

As above, remove the lamp and the N- E potential at the ceiling rose should disappear with the switch open.

 

[Eric12]

As above, remove the lamp and the N- E potential at the ceiling rose should disappear with the switch open.

Disappear at the switch aswell

 

[Eric12]

the diagram looks unorthodox, is this wired in singles ? If not then how is just one conductor feeding the ceiling light rose ??

 

[nicebutdim]

the diagram looks unorthodox, is this wired in singles ? If not then how is just one conductor feeding the ceiling light rose ??

OP is working on the assumption that a junction box is hiding somewhere, presumably in which switched line and neutral are reversed.

 

[DyFamCont]

Thanks very much for your help chaps.

It turned out to be reversed polarity and some dodgy DIY stuff. I'll go back another day to sort it.

Really appreciate the quick response though!