3C+E Ceiling light wiring

House_Hunter

Hi all,

Apologies - another ceiling light wiring question, though a little different from the norm...

Have replaced a quite afew few lights; most of which have even been mains in, mains out and switch loop - i.e. 3 sets of 2C+E wires.

Just came to the next light and this one's a bit different;
- 1x mains-in (2c+E)
- 1x mains-out (2c+E) (as you would expect)
- but then, the switch loop is a 3c+E??? (i.e red, blue, yellow and earth)

Wiring is,
terminal 1) Mains-in blk, Mains-out Blk, blue from 3c+e wire -> Neutral to light
terminal 2) Mains-in red, Mains-out red, red from 3c+e wire
terminal 3) Yellow from 3c+e wire -> live to light
terminal 4) All 3 earths..

Am I right here that the live goes down the red of the 3c+e wire to the switch, then come's back along the yellow. If yes, then why does the neutral have to go back to the switch?

ANy words of wisdom appreciated.

Cheers...

P.s. forgot to say, light is simple normal light operated by only a single switch.

DVardysShadow

House_Hunter wrote: »

Am I right here that the live goes down the red of the 3c+e wire to the switch, then come's back along the yellow. If yes, then why does the neutral have to go back to the switch?

P.s. forgot to say, light is simple normal light operated by only a single switch.

You are right about red and yellow. Probably the blue does nothing in the light switch. Surprised you have not popped that off the wall to see.

[Bet the light switch has a 2c+e red and black - which means that a feed to something else has been piggybacked]

House_Hunter

Yeah, was about to do that...but the OH has already painted the wall and made a nice little seal around the switch...

Instant way to get myself into trouble ruining that...so thought I would see what people's thoughts were first...

zax47

It seems like they needed to get a neutral down to the switch. Often neutrals are pulled down to switches to allow for 2nd gang to switch a fan (with timer) or anything requiring a permanent live, switched live and a neutral at the switch. You did say this is a single switch though - did you mean "switched at only one location" or "a single 1 gang switch".

Of course, it may not go to the switch - but be a neutral linked to a secondary circuit (would normally be wired in a single black though). Not good practice to "borrow" neutrals like this though.

Take the switch off and see what's behind it is my best advice.

House_Hunter

Sorry yeah - switched in only a single location....

The switch itself is a double gang switch though - the other operating the cupboard downlighters (its in the kitchen).

Hmm...looks like I might have to take the switch off the wall to get to the bottom of it then.

Possetjohn

Are you sure its only switched in one location? 3c & e are normally used for two and three way switching!

See http://www.ultimatehandyman.co.uk/two_way_lighting.htm

DVardysShadow

Possetjohn wrote: »

Are you sure its only switched in one location? 3c & e are normally used for two and three way switching!

See http://www.ultimatehandyman.co.uk/two_way_lighting.htm

However, 3c+e is also used to carry a switched supply and a permanent live. In this case, the blue is connected to neitral, so it will not be 2 way switching, although it might be the aftermath of a botched attempt.

zax47

Possetjohn, if it were wired 2-way (using RYB 3 core) then it wouldn't be connected how it is. The 3 core would be used as "strappers" between the two switches.

The 3 core has been used as the switch wire (red as feed & yellow as return), with the 3rd blue core taking the neutral somewhere (probably the switchbox).

Possetjohn

DVardys & zax,

Sorry didn't read the original post carefully enough. Why would anyone want to take a neutral back to the switch? Unless they wiring power through to the adjacent switch to the cuboard downlighters by also stealing the live from the switch loop? Very strange way to do it!

Househunter
Did you get to the bottom of it?

pdswindowsltd

it would seem to me that the reason for this is to power the cubpoard downlighters the neutral from the light fitting will probably be connected through in the back of the switch, both switches will use the same permanent live just with different switch wires in this case i would imagine for the main light the yellow and for the cupboard lighting will probably just be a 2c+E so a red.

DVardysShadow

pdswindowsltd wrote: »

it would seem to me that the reason for this is to power the cubpoard downlighters the neutral from the light fitting will probably be connected through in the back of the switch, both switches will use the same permanent live just with different switch wires in this case i would imagine for the main light the yellow and for the cupboard lighting will probably just be a 2c+E so a red.

That sounds very possible.