mystery wiring in ceiling rose

[colkav]

i am replacing an old light fitting with 4 downlights so i bought a quickwire switch and load fitting to accept the loop in and loop out and switch cables and then daisy chain the 4 lights out from the remaining load terminal in the qw. easy job im thinking but on taking the old light off to reveal the ceiling rose i am confronted by a wiring arrangement that doesn't add up.as you can see from the photo the loop in and out live and neutrals seem okay as does what appears to be the switch live (red wire) the mystery is the black wire on its own in the middle of the neutral terminal. this would logically be the other wire from the switch but surely that should go in the live terminal. all the lights work okay. can anyone shed any light on what this could be or how to proceed. thanks in advance

 

[telectrix]

you appear to have 1 neutral too many. could it be that anothelight has lost it's N and this has been bridged across?

 

[James]

How many switches are there on the faceplate?
There are possible reasons for doing what you have there but really needs checking and understanding before continuing.

 

[littlespark]

The outer red and blacks seem to be thicker.... sleeving?

I think I said on another thread.... please isolate the circuit before working on it. Those middle reds will be live even if switch isn’t off for room.

and where does floating earth wire go?

 

[SJD]

The extra N could well be a sheathed N single, e.g. to another fitting, some times come across wiring like around here when built (late-1960s/early-1970s builds).

In fact I've even been out to repair a non-working light in another room when someone has wrongly connected such a cable because they couldn't figure out what it was doing when changing a fitting.

In summary, make sure you keep the same connections, unless you fully understand what each cable does/goes.

 

[Timbo]

I'm wondering what sort of a mess is behind that backplate......?
Given that no sheathing is visible.

 

[colkav]

thanks for all replies. after doing some more digging(i am not a qualified lec.) it seems it may be a "borrowed neutral" . the rose is in a bathroom and its switch is shared with the landing light 2 way switch . it seems it was common practice to borrow a neutral fron an upstairs circuit back in the early 70's which this wiring is from. i should of mentioned this info. in the first post. i dont pretend to fully understand this borrowed neutral stuff so any further info or comment would be welcome, as to how to proceed with this. its a given that i will not do anything unless i'm 100% sure it's correct. thanks again. (i have an old wired fusebox with only 1 fuse for the who;e lighting circuit)

 

[James]

It is not a borrowed neutral if all the lights are on 1 circuit.
The term relates to the live coming from 1 circuit breaker and the N being fed back in common with the N from another circuit.

 

[telectrix]

It is not a borrowed neutral if all the lights are on 1 circuit.
The term relates to the live coming from 1 circuit breaker and the N being fed back in common with the N from another circuit.

which it possibly is. live feed to landing light from downstairs. i which case, i prefer to call it a borrowed live. as it's the live that's from a different circuit.

 

[DPG]

which it possibly is. live feed to landing light from downstairs. i which case, i prefer to call it a borrowed live. as it's the live that's from a different circuit.

All the lights in the house are on the same circuit though.

 

[littlespark]

Everything in the @telectrix house has been “borrowed”

 

[Flanders]

I think any work in a bathroom is notifiable and if you are altering the lighting circuit it needs to he RCD protect

 

[colkav]

thanks for all the replies, they have helped me make up my mind that the next step is to get an electrician involved. thanks again colin

 

[littlespark]

thanks again colin

You’re welcome...




Oh right... never mind.

 

[DPG]

Colin always gives the best advice on here.