Converting 2 Gang 2 Way to 1 Way

[VKM]

Hello,

I'm converting my switches to smart switches and have run into an issue with a 2 gang 2 way switch. I removed all wiring and then realised it's not so simple. Attached picture is from another post but similar to mine.

Downstairs switch is 2 gang with 1 controlling downstairs light and 1 the upstairs light in 2 way mode. Upstairs has 1 switch working 2 way to control the upstairs light.

What I want to do is remove the upstairs switch all together. Put a 2 gang 1 way smart switch downstairs (which has only 1 com and I'm OK to have both lights on same mcb). So I think it's the slave switch of the 2 way circuit I want to keep to control the upstairs light. The downstairs switch has its own COM for the downstairs light.

I connected the smart switch and the downstairs light works fine. But connecting the switched live of upstairs light and turning on causes the mcb to trip. I kept the permanent live coming from upstairs in a choc block and the COM of downstairs light in the Lin terminal of the smart switch.

Can someone help please to make this work?

 

[ericmark]

These are all two-way wiring diagrams. The centre one is the normal method, but one needs to do some testing to work out which has been used.

 

[VKM]

View attachment 402698View attachment 402699View attachment 402700These are all two-way wiring diagrams. The centre one is the normal method, but one needs to do some testing to work out which has been used.

Thanks. I have 2 gang switch at one point and both gangs use different perm live.

 

[robinbanks]

I removed all wiring

Using a multimeter in resistance mode, mark one cable as A, connect the live and earth cores together in just that one wire, then go to the other switch(and the rose) and use the meter between lives and earths and work out which cable is A, looking for 0 ohms(/listening for the beep).

Return to the start, separate the live and earth and repeat with another cable, marking it as B, C etc. Keep going until you have identified all cables at both ends (there will be one or two that are power in [and often out] for the radial that don't respond to this test)

Then return here with clear pictures showing all your markings, annotating them with upstairs, downstairs etc and we will tell you which wires to put where

Don't really fancy playing a game of "this other person's pics look like mine, can your work out how to wire my house from them?" for various reasons

If you don't have a multimeter they're a tenner from screwfix and well worth investing in if you're engaging in any amount of rewiring

 

[VKM]

Both lights are on different circuit breakers. I guess I can't combine Perm Live of both into one COM terminal on the smart switch.

 

[ericmark]

Correct, you need to keep each circuit independent, I have same problem, I have one switch plate with three circuits, so can't use a switch which uses a single common for all circuits.

I use smart bulbs instead for those circuits.

 

[VKM]

Correct, you need to keep each circuit independent, I have same problem, I have one switch plate with three circuits, so can't use a switch which uses a single common for all circuits.

I use smart bulbs instead for those circuits.

Thanks. I'll put separate switches then.

On another 2 way switch set, they are both on same circuit. So can I just cap off one Perm Live and stick the other one in COM of smart switch? And the Switched Live of both lights in L1 and L2?