in-line circuit?

[AndyandFenetta]

Hi - first post. Rather long-winded I expect. Apologies if this is obvious

I'm replacing a standard ceiling rose pendant fitting with new lighting necessitating connector blocks, and thought I knew what I was doing ... it looked like a standard loop in - 3 wires (twin and earth) in the rose, which I thought were feed in, feed out and switched (although this was not identified). So labelled, removed rose, joined the 3 earths together, joined the 3 L together, and then 2 N to one side of new light and 1 N (switched L) to the other. Switch on and ... light doesn't work.

Perhaps I'd remembered which was switch cable incorrectly (labels now gone) - so tried every pairwise combination of the N, but no luck.

Then engaged brain. Noted that the outside light circuit also runs from this rose, so made sure that it was still working OK - it has a separate light switch inside this room, and clearly everything is fine, switches on and off OK.

Beginning to scratch head, then looked inside the light switch itself for my inside light ... and didn't recognise the setup - two neutrals connected together in a block, and a single L cable in and out of the switch itself (and actually, also a linking L cable running to second switch which operates the wall lights and which are also still working OK so the circuit is live).

I think this is called an inline (?) method - which I'm not familiar with. I've looked at the next room and it has the same set up in the light switch, except there is only 1 cable at the rose (which is what I expected from this method). Funny, upstairs is all wired as loopin.

How can I have 3 cables at the rose if this is inline? Could two of them be the switch and feed and for the end of the loop, and then my inside light wired as inline? But all in the same rose?? Just looked in the outside light switch and this has 3 cables, 3 N in a block, 2 L into top of switch and 1 L from bottom.

Unfortunately, digging up the carpets and having a look from above is not possible.

Some urgency in getting this fixed asap w/e - my wife is about to have a a baby in the next week - probably in this room!!

Thanks for any help/advice

 

[jj4091]

Now you have removed the labels you are going to need a multi meter & the knowledge of how to use it to be able to establish what cable does what, if you want to go down that line then purchase one from your local diy store & look at the wikki for lightinging circuits or come back for more help. Or call a spark out.

 

[AndyandFenetta]

OK - I bought a cheap multi meter. Three twin core & E wires, call them 1 , 2 and 3. There is permanent connectivity between 1N and 2N (i.e. whether the switch is on or off), and between 2L and 3L. The switch establishes a connection between 1N and 1L. So definitely not a loop in system!

Then, I got out a piece of paper and worked it out! The only wiring diagram/explanation I could come up with was that wires 2 and 1 are a light feed and return; 3 is the feed from the circuit. In the light switch itself, 2N and 1N are permanently joined in a block, and the switch makes the connection between 2L to 1L. So the lamp goes between 1N and 1L, and the feed wire 3 (L, N) connects to wire 2 (L, N).

Tighten everything, cross fingers, and hey presto!

I would never have got this by guess work in a million years! So your advice - buy a meter - was spot on - Thanks!

One question - why would circuits be wired like this - surely lots of extra cable using light feed and return? (house is newly wired (c. 2 years ago)).

 

[Taylortwocities]

Ahh but it will not be light feed and return. It will be live and neutral to the light ( one cable) and live an neutral feeding on to the next light (one cable).
The last cable will go to the switch. this has two wires: live feed to the switch and switched live back to the light fitting (NOTE there is NO neutral here!)

This method actually uses less wire than the old method which used a (usually hidden)central interconnection box one on each floor of the house.

Congrats on your sucess.!