Wiring for a 2-way light switch to add a zigbee module

ashe

I recently (with the help of this forum!) installed a 4 bulb light in our hallway to replace a bog standard plastic ceiling rose.

Light looks great and room is now ready to paint and fill/sand around the current light switch however our entire home has hue lighting and heavily built into automations via home assistant and when it came to fitting the light, the glass globes were a few mm too short to fit the bulbs we use so we had to just use standard e14 filament candle bulbs.

I can't have one light fitting in the whole house not work with our ecosystem as it would drive me nuts, so am looking to fit a zigbee module in the backbox of the switch to allow home assistant to control that light outside of hue. I don't want to use hue's version of the module as it's nearly 3x the price and has a 5 year battery instead of just being powered.

Anyways, other challenge is the backbox fitted to my switch is quite shallow so to make it fit I would need either a deeper backbox or to sit this one further back in the wall, which is a solid wall but fairly soft as made out of thermalite blocks.

Forgive my pictures of the backbox here, as the wall has been sanded down roughly ready to fill and paint the walls and around the switch as I don't think previous owners decorated for some time! Also sorry these are huge as doesn't seem to be a way to resize them!

And this is the Zigbee module;

There are two cable entries at the top of the backbox

The one on the right;

* Earth to backbox terminal (then connection from there to the switch plate earth connector as it's a metal plate) 

* Red to COM at the top of the switch plate 

* Black to L1 at the bottom of the switch plate

The one on the left;

* Earth to backbox terminal again 

* Red to L2 at the top of the switch plate * 

* Blue to L1 at the top of the switch plate * 

* Yellow to COM at bottom of the switch plate

Switch plate in photos above is a double switch with one switch controlling the landing lights, and the other controlling the hall lights - the switch is in the hall. There is no switch in the landing for the hall, this is the only double switch we have. The light I want to control is the hallway light.

Can I get some guidance on what I need to wire up, and what I need to keep wired to the switch for the desired effect? There is a wiring diagram in the instructions but can never get my head round them. 

In my head I'll ;

* knock power off & undo screws, remove existing wires

* Remove the backbox

* Chisel some space out behind it to make it a little deeper and either push the backbox further back and use deeper screws, or install a deeper backbox

* Connect the cables up

* Close all back up and pair and test

FreeBear

That looks like a 16mm deep back box.

I'd opt for chiselling the old one out, making the hole deeper, and using a 47mm back box. That way, you have more depth to play with should you decide to fit an extra module. Just remember to put grommets in the knock-out holes.

FFHillbilly

you want to use diagram 1.
the red and black to the switch are permanent live and switched live, It's a guess as to which is which so you will have to test it. assuming they have used red as permanent live then:
red into "L in"
black into L out"
and then get 2 new bits of cable and connect S1 and S2 to Com and L1 in any way you want

ashe

FFHillbilly said:

you want to use diagram 1.
the red and black to the switch are permanent live and switched live, It's a guess as to which is which so you will have to test it. assuming they have used red as permanent live then:
red into "L in"
black into L out"
and then get 2 new bits of cable and connect S1 and S2 to Com and L1 in any way you want

Thanks, I'll give this a go. By "test it", will it just not work? Or do I need to do something additional?

If it helps, the wiring for the light, this was the old light wiring before I cleaned it up and fitted the new one; the light cable is the one on the right I believe. The black cable has a small red sleeve on it before it goes into the central terminal so I believe that is the switched live? Looks brown here but it was definitely red when I took it off.



In that case, using diagram 1;

Sonoff Module

L OUT black Wire
L IN - red Wire
S1 New piece of Brown Wire to COM 
S2 New piece of Blue Wire to S1 

Should I be indicating somehow that the black wire is in fact the switched live for future e.g the original wiring had some red sleeve,  should I apply some red tape?

ashe

FreeBear said:

That looks like a 16mm deep back box.

I'd opt for chiselling the old one out, making the hole deeper, and using a 47mm back box. That way, you have more depth to play with should you decide to fit an extra module. Just remember to put grommets in the knock-out holes.

I picked up a 35mm backbox at the hardware store yesterday when getting a length of wire. I think this should be fine and worst case can always set it a little further back. 

Interestingly the current back box isnt actually screwed in or anything but feels pretty solid, guessing the put it in when the plaster or whatever was wet and its just set around it? I've got a few screws to hold this one in place. 

FreeBear

ashe said: Interestingly the current back box isnt actually screwed in or anything but feels pretty solid, guessing the put it in when the plaster or whatever was wet and its just set around it? I've got a few screws to hold this one in place. 

Depending on how roughly I chisel out a recess (they can look real ugly sometimes), a dollop of bonding coat plaster goes in before bedding in the back box. The screws are just mechanical backup. This enables on to get the back box flush with the surface of the wall, and reduces the amount of filler needed to make good. If you don't have plaster, Fill & Finish will do the job.

Simonon77

ashe said:

FreeBear said:

That looks like a 16mm deep back box.

I'd opt for chiselling the old one out, making the hole deeper, and using a 47mm back box. That way, you have more depth to play with should you decide to fit an extra module. Just remember to put grommets in the knock-out holes.

I picked up a 35mm backbox at the hardware store yesterday when getting a length of wire. I think this should be fine and worst case can always set it a little further back. 

Interestingly the current back box isnt actually screwed in or anything but feels pretty solid, guessing the put it in when the plaster or whatever was wet and its just set around it? I've got a few screws to hold this one in place. 

Was very common in the past not to screw them in

ashe

FreeBear said:

ashe said: Interestingly the current back box isnt actually screwed in or anything but feels pretty solid, guessing the put it in when the plaster or whatever was wet and its just set around it? I've got a few screws to hold this one in place. 

Depending on how roughly I chisel out a recess (they can look real ugly sometimes), a dollop of bonding coat plaster goes in before bedding in the back box. The screws are just mechanical backup. This enables on to get the back box flush with the surface of the wall, and reduces the amount of filler needed to make good. If you don't have plaster, Fill & Finish will do the job.

Yeah it started off quite neat but then a big chunk came out 😂 all done & working, but the screw I put in is quite loose so I'll take the dual approach as you say and whack some full & finish in and then neaten it up at the wall 

FreeBear

ashe said:

FreeBear said:

ashe said: Interestingly the current back box isnt actually screwed in or anything but feels pretty solid, guessing the put it in when the plaster or whatever was wet and its just set around it? I've got a few screws to hold this one in place. 

Depending on how roughly I chisel out a recess (they can look real ugly sometimes), a dollop of bonding coat plaster goes in before bedding in the back box. The screws are just mechanical backup. This enables on to get the back box flush with the surface of the wall, and reduces the amount of filler needed to make good. If you don't have plaster, Fill & Finish will do the job.

Yeah it started off quite neat but then a big chunk came out 😂 all done & working, but the screw I put in is quite loose

With thermalite type blocks, I will drill the hole one size smaller than recommended for the plug. So if the gauge calls for an 8mm drill, I'll use a 7mm one. If the plug is still loose, a squirt of grab adhesive in the hole before (re)inserting the plug. Belt'n'braces approach for heavy duty fixings is resin fix. But that is way over the top just for a back box.

ashe

FreeBear said:

ashe said:

FreeBear said:

ashe said: Interestingly the current back box isnt actually screwed in or anything but feels pretty solid, guessing the put it in when the plaster or whatever was wet and its just set around it? I've got a few screws to hold this one in place. 

Depending on how roughly I chisel out a recess (they can look real ugly sometimes), a dollop of bonding coat plaster goes in before bedding in the back box. The screws are just mechanical backup. This enables on to get the back box flush with the surface of the wall, and reduces the amount of filler needed to make good. If you don't have plaster, Fill & Finish will do the job.

Yeah it started off quite neat but then a big chunk came out 😂 all done & working, but the screw I put in is quite loose

With thermalite type blocks, I will drill the hole one size smaller than recommended for the plug. So if the gauge calls for an 8mm drill, I'll use a 7mm one. If the plug is still loose, a squirt of grab adhesive in the hole before (re)inserting the plug. Belt'n'braces approach for heavy duty fixings is resin fix. But that is way over the top just for a back box.

Hm I don't have any grab adhesive, would some sticks like s**t do the job or does grab adhesive work differently? 

casper_gutman

Sticks Like Sh*t from Evo-Stik is a brand name for a specific grab adhesive.