Two way switching methods

[John D v2.0]

Hello, just a little conundrum as I'm wiring up some bedside lights with two way switching and had cause to think about the methods.

As far as I know there are topologically speaking two main ways of wiring up two way switches:

1. the old way - alternate both the live feed and the lamp between two intermediate points, or
2. the modern way - alternate an intermediate point with two switches between the live feed and the lamp.

As seen in this diagram - they are both of a case where the light is at the far end, although the former could be moved anywhere along the red line without affecting things.


However the only fundamental difference is that the former method requires three cores between the switches (but the third is a choice between a live or a neutral supply depending which end the light is), and the latter requires three if the light is at the near end, otherwise four are needed.

it seems in my mind the first method is more flexible, so should be alright in all situations. The only reasons against it seem to be various warnings about borrowed neutrals, warnings about interference if the neutral comes from elsewhere on the circuit. And maybe a chance to save on a wago if the supply goes through the first switch.

Have I missed something?

At present I am planning to do the "old way" with a 3+e cable where one switch is by the door, one is on the wall next to the switch, and the supply comes from somewhere in the ceiling. Rather than having to use an extra cable just for the neutral.

 

[EFLImpudence]

Doesn't it just depend on the wiring and locations?

That is, loop at switch or light and if the L And N are looped at the same.

 

[John D v2.0]

Doesn't it just depend on the wiring and locations?

That is, loop at switch or light and if the L And N are looped at the same.

so do you mean the scenario where you wanted to loop L&N supply via the second switch?
you would need 4 conductors between in both cases I think. So still not really any advantage for the "new" way is there?

 

[EFLImpudence]

I mean it depends on how you want to wire it - if new - or what you already have and the locations of the accessories.

Plus - a lot seem worried about interference.

 

[EFLImpudence]

I don't think you ever need 4 wires.

 

[John D v2.0]

fair enough thanks for that, so I'll just go ahead and wire it the way that makes more sense!
I agree you wouldn't need 4 wires, it would only be required if you wanted to use what I called the new way, with the light beside the far switch, remote from the supply. You'd need the 3 core for the lives, plus a neutral for the lamp.

 

[EFLImpudence]

Not really. You could use the old method in that case with the neutral as the third wire.

 

[John D v2.0]

thanks that's exactly what I'll do

 

[bernardgreen]

with the light beside the far switch, remote from the supply. You'd need the 3 core for the lives, plus a neutral for the lamp.

Earths not shown,

Put the lamp close to the far switch, Grey and Black need not be cut in the lamp, just coiled to provide enough slack in the Brown to get to the terminals in the lamp

 

[JohnW2]

... it seems in my mind the first method is more flexible, so should be alright in all situations. The only reasons against it seem to be various warnings about borrowed neutrals, warnings about interference if the neutral comes from elsewhere on the circuit. And maybe a chance to save on a wago if the supply goes through the first switch. Have I missed something?

I don't think you've missed anything - that's about it.

At present I am planning to do the "old way" with a 3+e cable where one switch is by the door, one is on the wall next to the switch, and the supply comes from somewhere in the ceiling. Rather than having to use an extra cable just for the neutral.

For what it's worth, that's what I (still) usually do when installing a new circuit. I think that I've only ever used the 'new' method when converting on-way switching to two-way - and I think that's the reason someone first came up with the idea, and called it the 'conversion' method.

As EFLI has said, what is more sensible/convenient is likely to depend upon the 'actual situation'.

Kind REgards, John