Two wires to single light switch

[paulg1]

What do you think of this? Am I missing something, because it makes no sense to me.

It's a light switch which controls a light at the end of a loop in circuit. It's a one way switch and I can't see why there would ever be a need to make this a two way switch (it's a downstairs cloakroom)

The associated ceiling rose has two cables up wired like this:
http://www.lightwiring.co.uk/wp-con...ng-rose-end-of-radial-old-colours-590x590.jpg (albeit with three core - grey wire unused)

There are two cables in the switch:

• Cable one is three core and earth with the grey wire unused (also unused at the ceiling rose), other than that it looks right.
• Cable two has live (brown) connected to the COM terminal and the black taped up. I presume there must be a grey wire cut off somewhere too as I can't see it.

I've got no idea why the second cable is even there.

 

[ban-all-sheds]

The associated ceiling rose has two cables

You've established that they are the same two that are at the switch?

I presume there must be a grey wire cut off somewhere too as I can't see it.

Why must there be? Maybe you can't see it because there isn't one?

I've got no idea why the second cable is even there.

Maybe it used to do something?

Maybe someone added it to add another light somewhere not realising there was no neutral to be had at the switch?

 

[chris1982]

Maybe someone added it to add another light somewhere not realising there was no neutral to be had at the switch?

And continuing that speculation, maybe they used the three core cable to be able to get a neutral to that box (in an unconventional way).

 

[ban-all-sheds]

Now there's a thought. (It's not unconventional, BTW - 'tis frequently suggested when people need to get a N there).

So it could be that permanent live comes in on the 3-core, to L1, that the taped ones used to be connected together, and the 2-core used to, or was meant to, supply SL+N to something.

But we could carry on speculating for no worthwhile reason.

What do you think of this?

A number of possibilities.

Am I missing something, because it makes no sense to me.

You're really the only one who can establish which cable(s) run between the rose and the switch, and therefore what all the conductors are for.

I can't see why there would ever be a need to make this a two way switch (it's a downstairs cloakroom)

Who has suggested that there might ever be, or was ever, such a need?

 

[EFLImpudence]

It's a one way switch and I can't see why there would ever be a need to make this a two way switch (it's a downstairs cloakroom)

Depends what he means.

It IS a two-way switch so does he - do you, Paul - mean two-way switch or two-way system?

 

[endecotp]

Dusconnect the mysterious spare cable and see what stops working!

 

[sparkwright]

As hinted by everyone else, unless you can trace where the second cable goes, it won't make a lot of sense.

I can only imagine some one has 'borrowed' a live feed from that switch, and they have obtained their neutral from somewhere else.

It looks like an amateur has done the work, it's not a very tidy job.

I WOULD suspect a grey wire has been snipped off, I don't think they make t+e in brown and black. Unless it's a very, very dark blue.

 

[sparkwright]

Send a picture of the wiring at the rose.

Your description of how it is comparing it with that diagram isn't as clear as it could be.

 

[paulg1]

To answer some questions:

• I indeed meant a two-way system, not a two-way switch
• I have not (yet) confirmed unambiguously which cable(s) run to the rose/where the 2nd cable goes. I take your points that this is the only way to be sure what the setup is here.

Finally, I never actually intended to change anything in the switch, my intention was simply to move the ceiling rose by about a foot. I just looked at the switch and thought something was unusual.

It looks like an amateur has done the work

Have to say as an amateur, I'm now tempted to get a professional to move my light fitting. If everything was perfectly standard I'd be OK - but there's clearly something odd here.

Send a picture of the wiring at the rose.

Too late I'm afraid. I did make notes before disconnecting it though:

Cable one

• Grey - snipped off
• Earth - Earth terminal in rose
• Brown - Loop block in rose
• Black - N block in rose

Cable two

• Grey - snipped off
• Earth - Earth terminal in rose
• Brown - Loop block in rose
• Black (with brown sheaf) - L block in rose

 

[endecotp]

I'm now tempted to get a professional to move my light fitting. If everything was perfectly standard I'd be OK - but there's clearly something odd here.

I think your light fitting sounds perfectly standard, and you shouldn't worry much about moving it yourself.

 

[ban-all-sheds]

To answer some questions:
I indeed meant a two-way system, not a two-way switch

Well yes, but nobody has suggested that there might ever be, or was ever, a need to make it a 2-way system, have they?

You do realise that it's perfectly OK to use a 2-way switch as a 1-way? Some people never bother to buy 1-way switches.

I have not (yet) confirmed unambiguously which cable(s) run to the rose/where the 2nd cable goes. I take your points that this is the only way to be sure what the setup is here.

Which you should do, if only because if there is a defunct cable which is still live it might be concealed unsafely somewhere, and need disconnecting.

Have to say as an amateur, I'm now tempted to get a professional to move my light fitting. If everything was perfectly standard I'd be OK - but there's clearly something odd here.

But if it all works fine now then it will continue to work fine if you move the light and make sure everything is reconnected as it was before.

Whoever did it was fond of using 3C+E instead of twin&earth, wasn't he...

Too late I'm afraid. I did make notes before disconnecting it though:

Cable one

• Grey - snipped off
• Earth - Earth terminal in rose
• Brown - Loop block in rose
• Black - N block in rose

Cable two

• Grey - snipped off
• Earth - Earth terminal in rose
• Brown - Loop block in rose
• Black (with brown sheaf) - L block in rose

Clearly those can't both be the cables going to the switch, so there is the issue of where does the other switch cable go.

 

[ban-all-sheds]

I WOULD suspect a grey wire has been snipped off, I don't think they make t+e in brown and black. Unless it's a very, very dark blue.

 

[paulg1]

You do realise that it's perfectly OK to use a 2-way switch as a 1-way?

Yeah I understand that - why bother to buy carry two different types when one does both jobs. The only reason I bought up two-way systems was to try to provide some background to what was likely intended when it was originally wired. I probably should have kept to the facts rather than trying to preempt you guys.

But if it all works fine now then it will continue to work fine if you move the light and make sure everything is reconnected as it was before.

This is a fair point. Now I'm curious about the random live wire snaking off though!

 

[ban-all-sheds]

You should be.

If you can't initially trace it easily, identify which is the switch cable for the light, disconnect the other one, and see if anything stops working.

 

[paulg1]

OK. I'll take a look tomorrow.

Whoever did it was fond of using 3C+E instead of twin&earth, wasn't he...

If it was the previous homeowner I suspect he bought a big roll cheaply and wanted to use it all up. It wouldn't surprise me - he also clearly had one phillips screwdriver which he used for everything: The number of ruined pozi screw heads in this house is phenomenal!