Three gang switch but only two cables, what's going on?

[harrypotter]

There's a three gang light switch that used to turn on three seperate lights. Two lights are disconnected now leaving only one light which is turned on by the middle switch. However, there's only two T&E cables going to the switch to control three lights which is what I'm confused about. Diagram below.

How does this work with three separate lights?

 

[EFLImpudence]

The reds in L1 supply the power and the other three wires go to the three lights.

Next!.

 

[crystal ball]

Two cables = 4 separate wires, one incoming live, three outgoing switched lives, neutrals will be sorted at the fittings and or JB

 

[harrypotter]

Thanks for the replies. What's the benefit of this method? Only needing 2 versus 3 cables down to switch? I'm also trying to understand how it's all wired at the JBs or roses. This way is confusing me

 

[EFLImpudence]

What's the benefit of this method?

Well, it is all that is needed.

Only needing 2 versus 3 cables down to switch?

As crystall ball said - it is four wires rather than the two cables; all four wires + earth could be in the same cable.

I'm also trying to understand how it's all wired at the JBs or roses. This way is confusing me

Just think of what you need as a minimum for one light and then what you need for the other two.

 

[EFLImpudence]

What would you actually need if all the switches were/are in the same place?

 

[pete01]

I'll have a guess 1 feed and 3 switch wires?

 

[harrypotter]

View attachment 318533

What would you actually need if all the switches were/are in the same place?

Yes I was thinking like that would mean 3 T&E cables down to the 3 gang switch. But if all all 3 switches were together in a 3 gang it would essentially be like the below, is that what you mean?

But then you'd have runs of just single wire no?

I also need to change one of the switches to 2 way. Is this possible with the two cable (4 wire in) setup? To be honest I'm thinking of just running 2 T&E cables and 1 3-core down to the switch as that's the way I know how to do it with one now being a 2 way. It's all original wiring anyway so wouldn't hurt to replace.

 

[EFLImpudence]

Yes I was thinking like that would mean 3 T&E cables down to the 3 gang switch. But if all all 3 switches were together in a 3 gang it would essentially be like the below, is that what you mean?

Yes sort of - depending on the location of the lights and the cable runs.

But then you'd have runs of just single wire no?

It depends how it is wired. You would (probably) have the two black wires actually running to the first light, then joined to other cables going to the second and third lights. You wouldn't actually use a single wire even if you did not need two.

I also need to change one of the switches to 2 way. Is this possible with the two cable (4 wire in) setup?

Yes.
You will need to run a 3core&E cable between the two switch positions.

To be honest I'm thinking of just running 3 T&E cables down to the switch as that's the way I know how to do it, especially now that I need one to be 2 way. It's all original wiring anyway so wouldn't hurt to replace.

Fair enough.
It might be more awkward than leaving it as it is depending on locations.
You don't need to alter anything to make one two-way apart from the extra cable between switches.

 

[Murdochcat]

To make one of the switches 2 way you need 3C and CPC from the existing switch to the new switch

 

[EFLImpudence]

 

[Mr Chibs]

As Duncan Bannatyne would say... 'I'm out' too confusing for me.

 

[harrypotter]

Yes sort of - depending on the location of the lights and the cable runs.


It depends how it is wired. You would (probably) have the two black wires actually running to the first light, then joined to other cables going to the second and third lights. You wouldn't actually use a single wire even if you did not need two.


Yes.
You will need to run a 3core&E cable between the two switch positions.


Fair enough.
It might be more awkward than leaving it as it is depending on locations.
You don't need to alter anything to make one two-way apart from the extra cable between switches.

Thanks for all the help, all understood now.

 

[harrypotter]

View attachment 318546

Actually sorry no, not fully understood haha. What if I wanted to make the middle switch the 2 way instead, would it be this?

If I messed it up, here's a blank diagram:

 

[EFLImpudence]

Yes, that is correct.

I would use Brown to connect to the supply reds, but it doesn't really matter.

Whatever colours you use, at the new switch you must use the same colour for the L1 or its equivalent.