DIY Doctor

Ceiling light loop-in wiring

Postby hedleyrowlands » Tue Mar 13, 2007 1:46 pm

Hi there

I have seen several questions regarding wiring a celing rose on a "loop-in" system, where there are 2 black and 2 red wires (plus earths) coming out of the ceiling (2 cores, each with 1 red, 1 black, 1 earth).

The answers referred the person to go to the "project" page, but the project page only appears to refer to the middle of a loop (with 3 reds & 3 blacks), and not, as I believe I have here, the end of an electrical loop. So please could someone describe in plain english how to do this?!

So I'll get to my question and could someone please assist without referring me to the project page?!

Problem 1 - Neither of the blacks has been tagged with red, so I don't know which is the "live" neutral. Annoying, but trial & error should fix this (tripping my fuse box in some cases). I have a volt meter, but not really sure how to use it - perhaps somebody could explain which setting it should be on and which wires at any one point I should attach to.

Problem 2 -
However, when I wire up my kitchen light (simple connector - 1 blue and 1 brown, no earth), I do the following (which I believe the correct way from referring to manuals and websites) with the following results:
- Both ceiling reds connected together using a connector block
- One black connected to blue
- Other black connected to brown
- both earths out of the ceiling connected together and tucked away.

Now remember I don't know which black is which, but which ever way round they are connected to the blue and brown, the light is permanently on - ie. the light is on even when the switch is "off". I get the same result if I swap the reds with the blacks - ie. connect the blacks together and then one red in to each of blue and brown.

I have actually tried about a dozen different configerations with my 4 ceiling wires in to the blue/brown. In some cases I have one red isolated from the whole picture (not connected to anything) and it still lights up!

I am so confused, and would really appreciate what I need to do to get this thing switching properly. I have not looked at the switch, but it did work as normal on the old light fitting.

Before anyone asks, I foolishly didn't write down how the old light was wired (thought I could remember, but after a new ceiling, 2 weeks later, I have forgotten). Hindsight's a wonderful thing... How hard can it be with only 4 wires from the ceiling!?

Many thanks for anyone responding!

Thanks Hedley
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Simply Build It

Postby Gloucester Sparky » Wed Mar 14, 2007 12:05 am

Could it be possible that you have a screw or nail penetrating your switch cable from the new ceiling you’ve had put up…….!

Assuming that the light is at the end of the circuit and you have one cable from the circuit and the other is the switch cable and these cables are bunched together. It is quite possible that a nail has penetrated the red wire of the circuit cable and then gone through the middle of the switch cable.

My concern is this, I don’t believe the nail would have missed the earth when it hit the switch cable so is it possible that the two cables are live in live out supplying a secondary light that is no longer there and the switching is done at a junction box under the floorboards.

Either way you need to lift some floor boards and start investigating.

I am sorry but that’s how I see it

Hope this helps
Gloucester Sparky
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Postby thedoctor » Fri Mar 16, 2007 2:24 pm

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Joined: Sat Apr 08, 2006 12:15 pm

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