Electrical wiring query

[DGP]

Just taken a ceiling light fitting down. 4-way chocolate block in - commoned grounds; two twins from attic wired lives commoned but going nowhere; returns wired: one to live of light fitting - one to return of light fitting. Why?

I don't want to guess what I'll find behind the light switch...

Think I've just worked out that this means it's the last ceiling rose in a looped circuit

 

[stevec67]

Just taken a ceiling light fitting down. 4-way chocolate block in - commoned grounds; two twins from attic wired lives commoned but going nowhere; returns wired: one to live of light fitting - one to return of light fitting. Why?

I don't want to guess what I'll find behind the light switch...

God knows, but if people don't understand how lighting is conventionally wired (UK at least) you get some weirdoes. I have fallen foul of this myself with an extractor fan wired on a lighting circuit and had to fix the cockup with a junction box and some proper wiring to make it work.

 

[Ian G]

That's a confusing way to write it but it's almost certainly the switch feed and return. Post a picture

 

[Marchbanks]

I think that sounds like the right hand side of this illustration from my Ladybird Book of House Wiring.

 

[stevec67]

I take it that you know the normal convention for a UK light fitting? If you haven't had it explained it's a bit counterintuitive. Sockets, whether on a ring or a radial, are much more straightforward to understand.

 

[DGP]

Thanks all - yes it's the last fitting in a looped circuit but there's no rose fitted so its just a bunch of wires hanging down into a very old piece of stripblock. Hence my caution.

 

[LecsonQuad]

If you rewire make sure you mark the switch drop return which is the black wire with a red mark in Marchbanks diagram. You will get confused quite easily if you don't.

 

[Barrymagrec]

When we moved into our new build flat forty odd* years ago the bathroom light switch also operated the extractor fan, as expected, what was not expected was that switching the light switch off stopped the fan but left the light on for 20 minutes. I looked behind the ceiling rose and there were more wires than you could shake a stick at but I eventually sussed them out and corrected the fault. My opinion of the electrician (s) was not improved by finding out that one of the kitchen sockets had live and neutral reversed.

* Very odd, some of them.

 

[DGP]

If you rewire make sure you mark the switch drop return which is the black wire with a red mark in Marchbanks diagram. You will get confused quite easily if you don't.

Wish the previous 'electrician' had done that courtesy for me!