Smart Switch Wiring Help

bash247 · 27 Nov 2020 at 11:37

So I've changed many switches in the past with no issues as the number of wires is usually simple to work out but in my recent home, I opened up the socket to replace it with a Sonoff T3-Black and it's completely baffled me with the amount of wires I saw behind it.

In the living room there are two lights which are controlled by the switch I'm trying not replace. On the other side of the room there is another switch that only turns off one of the lights.

Here is the back of the current light switch and the wires.

(Top brown is Common, Left is L1 and right is L2)

Now for the smart switch, I have the Neutral wire (blue, currently not in use) and live (Common wire in old socket). The remaining output is L1 out. Do all the wires go in that? Surely not.

Diagram for the smart switch below.

Thanks

Dava · 27 Nov 2020 at 12:16

are you wanting to keep the other switch or make it redundant?

its wired for 2 way switching so there will be a 'strapper' that goes from there to the other switch

bash247 · 27 Nov 2020 at 12:26

Dava said:
are you wanting to keep the other switch or make it redundant?

its wired for 2 way switching so there will be a 'strapper' that goes from there to the other switch

I would like to keep it functioning the way it is personally. The lighting can be bright at times so turning one off is handy.

Adam_151 · 27 Nov 2020 at 17:04

Just describe again how the switching functions, that switch has been wired for 2 way switching, so you should have another switch that you can turn the lights on and off from. But you are saying the second switch only turns off one of the lights thats been turned on by this switch? If so, I guess once turned off at that switch, it must be turned back on by the second switch?

bash247 · 28 Nov 2020 at 01:14

As you enter the room there's a switch that controls two lights (left & right)

On the other side of the room, there's another switch that only switches on/off the left light. If you were to go and turn off the left light using the secondary switch and go back to the main switch and try to turn the lights off. Both lights would "sync".

I tried the wiring today and planned to make the secondary switch redundant for now. Will need to buy a spacer as the switch doesn't fit

Adam_151 · 28 Nov 2020 at 09:36

bash247 said:
As you enter the room there's a switch that controls two lights (left & right)

On the other side of the room, there's another switch that only switches on/off the left light. If you were to go and turn off the left light using the secondary switch and go back to the main switch and try to turn the lights off. Both lights would "sync".

I tried the wiring today and planned to make the secondary switch redundant for now. Will need to buy a spacer as the switch doesn't fit

So I come into the room, turn the lightsswitch you pictured on, and on comes lights A and B, if I go to the other switch and flick it, light B turns off, but not A?, but if I then go back to switch 1 and turn it off, light A goes off and B stays off, if I flick it again both lights A and B come back on?

Sounds most odd, does the reverse work? I.e. use switch 2 to turn on light B and then switch 1 brings light A on as well, but then if you turn switch A off, both go off again?

Can we have a picture of the wiring in switch 2?

jpaul · 28 Nov 2020 at 12:29

as Adam says, sounds odd

The original is a double throw switch - to support a left bulb two way lighting capability which you described.

but the sonoff is a single throw, so, all you can do, is wire secondary switch in series, such that, if you turn off light with secondary switch, you have to use that, to turn it back on, in addition to using the smart switch.

you probably have this http://www.lightwiring.co.uk/tag/2-way-lighting-circuit-diagram/ with right bulb just connected to one of terminals on left switch in picture.

so, looks like you will just have to hide the two wires going to L1 ... BUT there is an additional brown going to both L1 and L2 than is needed just to connect up two light roses.

[
Interesting - just learned sonoff do have a smart switch supporting 2 way lights - neat - but, that wouldn't solve your problem, as right bulb then could't be controlled
https://www.amazon.co.uk/Compatible-Control-Function-Support-Required/dp/B07TRSWY23
]

lewism · 28 Nov 2020 at 23:31

Common in that switch isn't your feed. Judging by the the two cables coming in the right hand side that would be your feed in and out and supplying the permanent feed on the grey core and thus your brown with the black core is the cable going to your light(s)

So basically you need the two browns that go with the grey to go to your L in and the other brown that's with the black goes to your L1. The other cores on the three core (brown/black/grey) can be put in connector and left. Don't cut them out.

It's called the Dundonian two way up here because it saves you running an extra cable from the furthest away switch up to the light. This method you take everything to one switch instead.

Mocked up a quick diagram so you can see what I mean.

bash247 · 29 Nov 2020 at 01:51

Adam_151 said:
So I come into the room, turn the lightsswitch you pictured on, and on comes lights A and B, if I go to the other switch and flick it, light B turns off, but not A?, but if I then go back to switch 1 and turn it off, light A goes off and B stays off, if I flick it again both lights A and B come back on?

Sounds most odd, does the reverse work? I.e. use switch 2 to turn on light B and then switch 1 brings light A on as well, but then if you turn switch A off, both go off again?

Can we have a picture of the wiring in switch 2?

This sounds the most accurate. I will open the 2nd switch and show the wiring. I managed to use a spacer to screw the sonoff switch to the wall to hide the exposed wires.

bash247 · 29 Nov 2020 at 01:52

lewism said:
Common in that switch isn't your feed. Judging by the the two cables coming in the right hand side that would be your feed in and out and supplying the permanent feed on the grey core and thus your brown with the black core is the cable going to your light(s)

So basically you need the two browns that go with the grey to go to your L in and the other brown that's with the black goes to your L1. The other cores on the three core (brown/black/grey) can be put in connector and left. Don't cut them out.

It's called the Dundonian two way up here because it saves you running an extra cable from the furthest away switch up to the light. This method you take everything to one switch instead.

Mocked up a quick diagram so you can see what I mean.

Should there be more than one image? I can only see one them

lewism · 29 Nov 2020 at 10:07

No, just the one. I couldn't get it to upload correctly and couldn't delete the extra links for some reason.

jpaul · 29 Nov 2020 at 17:17

my thinking was - since the right light remains on irrespective of the secondary switch. that should indicate common is the in-feed

lewism · 29 Nov 2020 at 21:52

jpaul said:
my thinking was - since the right light remains on irrespective of the secondary switch. that should indicate common is the in-feed

It may very well be, I'm not sure what he means but syncing up and without seeing them other switch it's hard to say.

bash247 · 3 Dec 2020 at 11:13

Apologies for the lack of update but work has been extremely busy. The photo below is the wiring for the second switch.

lewism · 4 Dec 2020 at 18:54

So it appears I was correct, your other light appears to be on another switch entirely. As those are two 1 gang, two way switches.

You'll need to find out what one is your supply cable (use a volt pen) and what ones go to your light. And wire them in to your smart switch accordingly.

You shouldn't need any more help than that but if you do. Get someone who knows what they are doing as this is basic stuff for an electrician.