Ceiling rose confusion

[R D S]

Taking my bathroom light out, the wires only just protrude from the ceiling, it appeared that I had one each of live (red), neutral (black) & earth but as I pulled the chock block away I had 2 black / 1 red / earth.

I've connected the light such that the blacks are together and it works fine.

But i've looked in the switch on the wall and that has a red live feed to the switch and a black on the other side.

So now when I turn the bathroom light on, presumably i'm sending juice into the other black wire, which is causing me concern.

But the only other option would be connecting a red & black together, which also seems illogical.

Hopefully Mr W will be along shortly!

[R D S]

Although when I test with the light on, the red at the light is live and blacks aren't.

[John Rumm]

Perhaps, but you you can make do with me for the mo ;-)

A picture helps here. Have a look at the 'Simplified "loop in" wiring' diagram here:

not quite clear from your description exactly how yours is wired, but it will likely be a variation on this theme. You may not have a cable out to the "next" light if this is the last one on the circuit.

Typically there will be cable that runs from the rose to the switch. That would ideally need two live wires - one permanent live in, and then a switched live out. Typically however it gets wired in "normal" red/black or brown/blue cable. Hence the neutral wire needs to be re-purposed as a live. This should be done with sleeving or tape to mark the fact its being used as a live, but again this is not always there.

[Andy Wade]

Is this a 1960s or 70s house with the lighting wired in sheathed singles, or regular T&E wiring?

If it's working then you can't have connected the switched line to a neutral - that would cause a short-circuit when you switched on and blow the fuse or trip the MCB. But it does sound as if the switched line is black (with missing red sleeve) at the switch end and red at the rose end. There may be an intermediate junction box where the colour changes.

Check with a voltmeter to earth that the blacks at the rose are indeed neutral and the red is really the switched line. If that's the case It's probably OK.

... but not unknown, especially if alterations have been made previously...

[ARW]

> Its not quite clear from your description exactly how yours is wired,

Too many variables.

It could be a circuit wired up like this

someone has moved a lightswitch using T&E to extend the circuit to the new switch position, or it could be a juction box setuup where someone has later taken a neutral from the light fitting.

Rick seem to have onlt one red and one earth so the singles option looks looks more likely.

[newshound]

If it is any comfort, I once rescued a Medic who had trained or done research at Oxford, Cambridge, and Princeton from the results of his DIY where he connected all the reds together and all the blacks together, to the two terminals of his new ceiling light.

[R D S]

At the switch there is a T&E, the red is live and the black goes live on switching.

There are 2 'single' blacks in the ceiling and a T&E with only the red and the earth visible.

At the ceiling, With the switch on, there is power on the red but nowhere else.

So i'll put it back with the neutrals together, I just don't get why the black wire leaving the switch emerges red at the light.

I've taken a couple of pics but i'm not sure they'll help.

[Roger Mills]

And I once rescued a minister of religion who had wired a wall light such that, with the switch off, the light was on - but when you moved the switch to ON, you got a big bang!

[John Rumm]

>>> Its not quite clear from your description exactly how yours is wired,

Yup...

> where someone has moved a lightswitch using T&E to extend the circuit to the

Or even a combination of the last switch on the circuit, but not the last rose! That would give you two wires at the switch, where the black is the permanent live, and three wires at the rose with neutral in and out, and a switched live in.

[Toby]

and the twin and earth is feeding the light and the two additional blacks, which look like singles, are neutrals that are going somewhere, feeding something else. if you just connect the light to the twin and earth. does it still work, and if so do other lights elsewhere stop working?

[Steve Firth]

Roger Mills wrote: [snip]

I got called in by a neighbour to help rewire his wall lights. They were controlled by DPDT switches and the electrician had left him instructions on how to wire in the light fittings.

Somehow he had managed to wire them up so that flipping the switches resulted in OFF-DIM-BANG.

I was impressed.

[Tony Bryer]

Be careful - relay too many stories like this and TPTB will decide that the UK needs to copy Australia (all work to fixed wiring to be done by licensed sparks). The irony is that residents of this parish would be horrified by what is standard practice here: no concept of zones and cables run through stud walls following random routes (not the shortest, just random!)