DIY Doctor

Replacing 3-Gang Switch With a new Smart Switch

Postby jonbut34 » Wed Jan 22, 2020 3:14 pm

Hi Guys,

I have a 3 gang switch, where one of the switches is 2-way, with another switch for the same lights on another wall.

I'm looking to replace the 3 gang switch with a new smart switch, however the smart switch has simply Neutral In, Line In, and 3 x Live Out.

Old Switch https://pasteboard.co/IR9Yl02.jpg
New Switch https://pasteboard.co/IR9YC6G.jpg

Apologies for the upside down / dodgy images, had to find somewhere to host them.

If I were to put the new switch in and treat it as three individual switches, would it break anything? I guess the switch on the other wall would stop working? But would it break anything else? Alternatively, is there a way I can wire it such that the other switch would also work?
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Postby Mr White » Wed Jan 22, 2020 5:58 pm

Your thinking is correct, the switch on the other side of the wall will become redundant.

I hope for you that the blue wires just in the picture are neutral (And have you proved it, and if so how?) as without a neutral your new switch will not work.
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Postby jonbut34 » Wed Jan 22, 2020 6:54 pm

Mr White wrote:Your thinking is correct, the switch on the other side of the wall will become redundant.

I hope for you that the blue wires just in the picture are neutral (And have you proved it, and if so how?) as without a neutral your new switch will not work.


They are neutral. It's a new build house, and apparently they put them in there now (I found this out before I bought the switch). The other (single gang) switch I installed I put another wire in the blue block and into the switch and it works now :)

The confusion for me here is that there are wires everywhere! And some little ones linking each switch. I assume that's the live right? I assume COM is live and the opposing wire is the switched live, but some of these switches appear to be reversed.

I'm okay with very simple electrics (like the 1 gang simple switches or plug sockets), but this is a little more confusing, so before I take this on I'd like to understand a little more to make sure I don't do something silly.
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Postby ericmark » Thu Jan 23, 2020 12:02 am

Electronic switches use an S wire instead of the com wire for 2 way switching and it is NOT 230 volt the S wire must never connect to mains.

There will be a master switch and slave switch, it does NOT use old two way switch.

I see nothing on the new switch that would allow it to work as two way, there are two ways to wire two way switching, one takes power into com and light comes out of com on other switch, I don't like that method as it needs connector blocks inside light switch.

The second is power in goes to 2 way and power out 1 way the switches are connected like to like, com goes switch to switch but know where else.

It seems likely your switch uses second method, so there are three wires going between the two switches seems likely switch on the right?

So from what I can see, likely bottom right wire which goes into com goes to other switch, likely other two wires are black and grey and are in 1 way and 2 way top right. So likely the brown wire in top right 1 way needs moving to com, and the three and earth cable made safe to remove the two way switching.
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Postby jonbut34 » Thu Jan 23, 2020 10:15 am

Hi,

Thanks for the explanation. I think I'm slowly getting there...

I watched this YouTube video to try to get a better understanding and from what you mentioned, it seems this is the first example of 1 way switching on the video? https://www.youtube.com/watch?v=opoEswRp_jg

I've annotated my image, to ensure I've got a firm understanding of what's going on. But some things are still not clear. If my annotations are correct, why is there a wire going from the centre com (which I believe to be live) to '2 way' on the left switch. If my thinking is correct, that should be a switched live to the other switch?

https://ibb.co/tLgKswC

Many thanks for all the help here, it's greatly appreciated.

Thanks
Jon
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Postby jonbut34 » Mon Jan 27, 2020 11:53 am

Anyone been able to check out my image? Hoping to get some clarity on this.

Thanks
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Postby ericmark » Thu Jan 30, 2020 12:22 am

With a simple on/off normally power in to com, and out either L1 or L2 which is used swaps if on is up or down.

With two way switches power into L1 and out of L2 and switch will not work unless other switch fitted.

[attachment=0]two-way-real.jpg[/attachment]

Does the diagram help?
Attachments
two-way-real.jpg
two-way-real.jpg (47.51 KiB) Viewed 101 times
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