Wiring for lights

[Dave]

This afternoon, I have been replacing a light fitting in a storage area that got broke last week.

I took off the old fitting, there was a green sleeved wire going to the light fittings earth point (the fitting was all plastic). A black wire going to one side of the bulb holder, a red going to the other side of the holder (this cable also carried the earth I mentioned above) and a black wire that did not look as if it had been connected to anything.

I fitted the new light, only to find that the rest of the downstairs lights were not working. After a bit of head scratching I decided that the two black wires must be neutrals and joined them together. The house lights came back on.

Is it normal to loop neutral cables to light fittings? By the way, this is the light fitting closest to the fuse box.

Dave

[Tournifreak]

Yes.

[Dave Stanton]

Yes, more to the point, why do you think it would not be normal ?

Dave

[John]

I would look at the light wiring. If it's a ring, you've got another break in the neutral.

[Dave]

Just that from what I have read from here, the loop goes from one ceiling rose to the next, until it gets to the end, using 3 red, 3 green and two black plus a black with a red sleeve. I thought this was the norm.

Dave

[Dave Stanton]

And what are the blacks, neutrals!. Or as it will be from now on Brown, Blue and Green/Yellow. Dont forget the one cable is the switch cable which uses Red (Brown) to feed the switch and the return uses the Black(Blue)which is suitably marked with a sleeve as you said. So actually only two cables form the loop

Dave

[David Hansen]

On 11 Mar 2006 12:11:40 -0800 someone who may be "John" wrote this:-

Lighting circuits are not arranged as rings. There is no need or advantage.

Some people do claim that they have installed lighting circuits as rings in their own house. If they have I would question their competence.

[Bob Eager]

Isn't his point here that *only* the neutral is apparently looped? Only one line and only one CPC, but two neutrals?

[Mungo]

Good point. And if the neutral has been "borrowed" then you could get in to territory where you can receive a shock even with the main circuit power off (as I found to my cost a few years ago).

Search on "borrowed neutral" in this newsgroup for details.

Mungo

P.S. With the new colours, do folks sleeve the live with brown tape or are you all waiting for your reel of red tape to become exhausted first?

[ARWadsworth]

Using a loop system such as

is the norm on many houses. It is quick and easy for the electrician to install, especially if pendants are to be fitted. It make it harder to fit lightfittings afterward.

You wiring is done on singles. Councils seem keen to wire their houses in singles for some reason.

Singles wiring loops the live wire at the switch and the neutral wire at the light so that you have three reds at the switch (2 for the loop and a switch wire)and two blacks (neutrals) and one red (switch live) at the light.

The earth is usually part of the live wire.

Adam

[mike]

Dave wrote in news:duvhpj$ibh$ [e-mail]:

I agree with you, though I'm a bit afraid to say so here.

An isolated (in the out there on it's own sense) IMO should have just a switched live and a neutral (and earth)

Any looping should be done at the rose or the junction box where the fitting is wired from; anyhow thats the way I do it.

Otherwise you get confusion, and confusion can be dangerous.

Now I'll duck

mike

[Bob Eager]

I bought a jumbo pack of lots of colours (including green/yellow stripe) a while ago. So I use whatever should be used...I have them all!

[Dave Stanton]

[Lobster]

And similarly, if you're working on a system with the old-colour wiring, must you use matching old-colour sleeving? And if that can no longer be obtained...?

Where d'you get that from?! I was going to buy some last week from Screwfix, until I found their minimum order was for 100m! (bit silly baulking at that as it's only 3.50, but that's just me - I wouldn't be able to bring myself to bin the 90m I didn't need, and it would clutter up the garage for the next 25 years).

David

[Bob Eager]

CPC...but it was a while ago and can't find the part number in my records..

(/me looks in catalogue....)

Here we are... CBBR7226 5.50 for pack of 24 rolls, 10 black, 2 red, 2 white, 2 yellow, 2 blue, 2 brown, 2 green, 2 green/yellow. 5 metres/roll, 19mm width.

[Dave Stanton]

Are we going to offer a prize for the first one someone finds that has red tape on the blue core ?

Dave

[Mungo]

Errr... if it's red tape on a blue wire then guilty as charged. I advocate installation of three-core and earth with lighting circuits, mainly as a contingency to save me re-stringing a new cable when SWMBO decides on a new light switching arrangement. And the old 3-core used to be red yellow blue (now brown black gray IIRC). So sometimes (two-way-switching) the blue is switched live. Hope I'm not barking up the wrong tree.

Mungo

[Dave]

I think that this was what confused me when I stuck a volt meter acros the wires.

I found one neutral, one earth, one live feed and one switched live. What I did not take into account was that another light switch was set to on and the neutral was showing as a live feed was in fact another neutral that was live from a normal wired switch (all the rest of the house has 3 cables to the light) that was switched on.

I hope you understand this

Dave