Turning a dumb 2 way light switch into a smart 3 way light switch

techno79

Member
I have a 6 spots lights (that are capable of being dimmed) in the hallway controlled by a 2 way light switch (one at the top of the stairs and one at the bottom). I wanted to make this smart so my thinking was to add a Shelly Dimmer module where the first spotlight is.

Q1. Just to check, if I'm installing it at the spotlight, I still only need one Shelly Dimmer even though it's a 2 way switch?

I realise the standard dumb toggle switches won't allow me to dim but I will still be able to dim using my phone or some home automation software routines so this is fine. However, it would be more convenient if I could install a 3rd switch in a different location so I was thinking of a battery powered smart switch that would trigger a home automation routine to toggle the state of the light. Effectively, this would allow me to have a 3 way light switch where any switch would toggle the light switch (and the smart switch might even be able to dim as well).

Q2. Will this work using the Shelly Dimmer or is there a better option?
 

Seb Briggs

Distinguished Member
Hi

Yes just one dimmer module needed .

I would change the toggle switches to 2 way centre off retractive switches so you can sim form them

If you can get power to the 3rd location the you can use a Shelly I3 as a scene controller with a range of options to control a dimmer or run a scene
 

techno79

Member
Hi

Yes just one dimmer module needed .

I would change the toggle switches to 2 way centre off retractive switches so you can sim form them

If you can get power to the 3rd location the you can use a Shelly I3 as a scene controller with a range of options to control a dimmer or run a scene
Is there a particular brand that you can suggest? Something sold by Screwfix/Toolstation would be idea but I'm in NW London so TLC Direct and RS Components are also nearby too.
 

techno79

Member
Is there a particular brand that you can suggest? Something sold by Screwfix/Toolstation would be idea but I'm in NW London so TLC Direct and RS Components are also nearby too.
I might need to go for a modular switch system because the 2 way switch are both on a double sized gang of 3 switches. The other 2 switches on the gang would be staying as a normal toggle switch.
 

techno79

Member
Having a look on TLC Direct, I can see Varilight have their PowerGrid range (Varilight PowerGrid Brushed Steel). They do a 3 gang plate so I would need 2x normal toggle switches and 1x 2 way centre off retractive switch for each gang plate.

So, in terms of shopping list. Is the following correct:

3 gang plate: 3 Gang PowerGrid Plate (Twin Plate) c/w Grid Frame - Screwless Brush Steel | Varilight (XDSPGY3S)

2 way centre off retractive switch: 10 Amp 2 Way & Off Retractive PowerGrid Switch - Brushed Steel | Varilight (G102SRS) (it says it's 10 amps, is this the right rating)?

Normal toggle switch: 10 Amp 2 Way PowerGrid Switch - Brushed Steel | Varilight (G102SS)

Just for info, I will get an electrician to install the above but they aren't very good at recommending products but will happily fit what I've provided. Hoping I can order all the bits for when they come so they can install it all without issue.
 

Seb Briggs

Distinguished Member
Couple of diagrams for you
 

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Seb Briggs

Distinguished Member
Having a look on TLC Direct, I can see Varilight have their PowerGrid range (Varilight PowerGrid Brushed Steel). They do a 3 gang plate so I would need 2x normal toggle switches and 1x 2 way centre off retractive switch for each gang plate.

So, in terms of shopping list. Is the following correct:

3 gang plate: 3 Gang PowerGrid Plate (Twin Plate) c/w Grid Frame - Screwless Brush Steel | Varilight (XDSPGY3S)

2 way centre off retractive switch: 10 Amp 2 Way & Off Retractive PowerGrid Switch - Brushed Steel | Varilight (G102SRS) (it says it's 10 amps, is this the right rating)?

Normal toggle switch: 10 Amp 2 Way PowerGrid Switch - Brushed Steel | Varilight (G102SS)

Just for info, I will get an electrician to install the above but they aren't very good at recommending products but will happily fit what I've provided. Hoping I can order all the bits for when they come so they can install it all without issue.
That sounds right
 

techno79

Member
@Seb Briggs I'm hoping you might be able to help. I've ordered a bunch of Shelly devices and some Varilight 2 way centre off retractive switches to go with them. The light switches themselves only have live, switched live and neutral wires. However, most of the Shelly Dimmer devices will be installed at the spotlight in the ceiling.

I've had an electrician come around and he's a little confused with the L1 and L2 and said that the switches do not currently have the correct wiring:
Shelly wiring diagram.JPG


I didn't think the light switches needed any other special wiring to use with the 2 way retractive centre off switches.

It could just be a misunderstanding but anything you can shed more light on to me explain to the electrician?
 
Last edited:

Seb Briggs

Distinguished Member
@Seb Briggs I'm hoping you might be able to help. I've ordered a bunch of Shelly devices and some Varilight 2 way centre off retractive switches to go with them. The light switches themselves only have live, switched live and neutral wires. However, most of the Shelly Dimmer devices will be installed at the spotlight in the ceiling.

I've had an electrician come around and he's a little confused with the L1 and L2 and said that the switches do not currently have the correct wiring:
View attachment 1685718

I didn't think the light switches needed any other special wiring to use with the 2 way retractive centre off switches.

It could just be a misunderstanding but anything you can shed more light on to me explain to the electrician?

On the back of the retractive switches there should be terminals labelled com, L1 and L2 see below


IMG_0924[1].JPG IMG_0925[1].JPG

Quite simply they need a wire from L1 and L2 on the switch into the dimmer module terminals SW1 and SW2 and another from com on the switch to L on the module


If the module is in the ceiling rose then the same applies but they may have to repurpose wires for L1 and L2 .
 

techno79

Member
On the back of the retractive switches there should be terminals labelled com, L1 and L2 see below


View attachment 1685734 View attachment 1685735

Quite simply they need a wire from L1 and L2 on the switch into the dimmer module terminals SW1 and SW2 and another from com on the switch to L on the module


If the module is in the ceiling rose then the same applies but they may have to repurpose wires for L1 and L2 .
So if the Shelly Dimmer is going up at the spotlight, does that mean the existing 3 conductor wires going to the light switch (live, switched live and neutral) are re-purposed into L1, L2 and COM?
 

Seb Briggs

Distinguished Member
So if the Shelly Dimmer is going up at the spotlight, does that mean the existing 3 conductor wires going to the light switch (live, switched live and neutral) are re-purposed into L1, L2 and COM?

Yes if that is possible that is how its done, best if the wires are sleeved and labelled to help in the future
 

Seb Briggs

Distinguished Member
Does it all work now ?

A tip if you are doing lots of modules is to add them to the app before installing them in the wall .
 

techno79

Member
@Seb Briggs thank you so much for your help. You've been super helpful.

I haven't actually setup the devices on the app yet. I should get that done but I'm working from home so I'm extremely strapped for time to do this now. I'll have to take a gamble that it'll all work fine when I've finished work but this'll be after the electrician has gone. He's had some other challenges though with the specific downlight holders as the electric cables for them are not that long so it's made it difficult to get them installed. Plus he's putting in the Shelly Dimmers into choc boxes so they're more protected so that takes up more space but it feels like the safe thing to do.
 

techno79

Member
I'm sure I'll get there in the end but the other challenge is getting a Shelly device for bathroom lights which have a bathroom fan linked to it (i.e. fan comes on when the lights are on). Apparently this won't work because if the lights are dim then it won't supply the fan with enough voltage. I feel I needed to do more research before venturing down this path.
 

Seb Briggs

Distinguished Member
I'm sure I'll get there in the end but the other challenge is getting a Shelly device for bathroom lights which have a bathroom fan linked to it (i.e. fan comes on when the lights are on). Apparently this won't work because if the lights are dim then it won't supply the fan with enough voltage. I feel I needed to do more research before venturing down this path.

My advice is to de-link the fan from the light and connect it to a Shelly relay independently.

You can then use the app to create a scene to only turn on the fan when the light is switched on , or more cleverly only turn the fan on when the light is switched on and its before 11PM and after 6AM (example).
 

Seb Briggs

Distinguished Member
@Seb Briggs thank you so much for your help. You've been super helpful.

I haven't actually setup the devices on the app yet. I should get that done but I'm working from home so I'm extremely strapped for time to do this now. I'll have to take a gamble that it'll all work fine when I've finished work but this'll be after the electrician has gone. He's had some other challenges though with the specific downlight holders as the electric cables for them are not that long so it's made it difficult to get them installed. Plus he's putting in the Shelly Dimmers into choc boxes so they're more protected so that takes up more space but it feels like the safe thing to do.

Hopefully your Wifi (2.4Ghz) is strong enough around the house, especially when the modules are installed in the ceiling and then in a chocbox. Its why I pair them first as tricky to get to them once installed.
 

techno79

Member
The fans can be triggered via pull cord as well as it having a humidity sensor, so the other option is to delink it entirely to the light switch trigger. But I'll leave that for another day as the electrician will almost certainly have to do another visit to finish things off and in the meantime, I can do some research over the best way forward for the remaining stuff.

Thanks again for your help.
 

techno79

Member
I managed to setup one of the Shelly Dimmers in the app but I'm finding the Shelly mobile app (Android) really flaky. It discovers the Shelly Dimmer but when I go to add it to a room the app seems to hang showing a spinning progress indicator and it doesn't move on from there. I had the same problem when I was adding some Shelly Flood sensors. Hardware seems good, but the mobile app does seem quite flaky.
 

Seb Briggs

Distinguished Member
I managed to setup one of the Shelly Dimmers in the app but I'm finding the Shelly mobile app (Android) really flaky. It discovers the Shelly Dimmer but when I go to add it to a room the app seems to hang showing a spinning progress indicator and it doesn't move on from there. I had the same problem when I was adding some Shelly Flood sensors. Hardware seems good, but the mobile app does seem quite flaky.
Sorry don’t know the android app but the apple version is just about rock solid
 

techno79

Member
Ah okay. Android app seems okay once it's setup but the bug seems to be related to when you add a device to a room. Might have to borrow an Apple device to setup things and then continue using the Android app. Thanks again for your help :)
 

techno79

Member
Wow...I have had some challenges with the Shelly Dimmer. I'll list them below and hopefully it might help others or others may share how they overcome these.

Can't fit Shelly Dimmers in the back box
It is extremely difficult to fit Shelly Dimmers in the backbox of the light switch. Just about managed to fit one in a one gang back box but only by change the 35mm deep back box to a 45mm. I have no idea how anyone can fit more than 1 Shelly Dimmer in 2, 3 or 4 gang back box. For this reason, the electrician installed the Shelly Dimmers up in the spotlight space which lead to another issue as mentioned next. Will be interesting to know how other people manage to get more than 1 Shelly Dimmer in the backbox even with a 45mm one?

Not enough wires at the light switch
When I had my wiring re-done, I asked to have neutral wires at all the light switches. However, the silly "electrician" who did this at the time did not have a clue about smart lighting systems so all the light switches were wired with traditional twin and earth cables. When I told them they needed a neutral as well, they then run a single blue core wire from the spotlight to each switch plate. However, in some places, they didn't take a direct connection from the light, they simply chained the connection from a neutral from another light switch on the other side of the wall. It was a pretty big botch but from my limited understanding at the time, all the light switches had neutral wires so it was fine. This would have been fine if the Shelly Dimmer was installed at the light switch.

However, with the Shelly Dimmer being installed at the spotlight, then it seems like every switch on the switch plate needs 3 wires. If it was a 3 gang plate then you can use one of the neutral wires for one switch but then the other two switches wouldn't have enough wires for this.

And obviously, this couldn't be used for the light switches that took a neutral chained from another light switch.

Overheat warning on Shelly Dimmer
I have one room that has 12 LED spotlights (5W each). This means that a total of around 60 watts would be running when at full brightness. However, the Shelly Dimmer installed here will often alert about "Over temperature detected". I thought the Shelly Dimmer could handle way more than 60 watts but this doesn't seem to be the case.

For now, I get around this by not putting the lights at 100% brightness. If I put it to no more than 80% then it seems to be okay.
 

Seb Briggs

Distinguished Member
Very useful

A few notes to add



The problem with mounting in the ceiling and requiring 3 wires only occurs if you have a retractive centre off switch, so you can dim neatly at the switch. If you have a momentary or toggle switch you only require 2 wires. A momentary switch would still allow dimming at the switch just not as neatly as a retractive. A toggle switch wouldn't allow dimming at the switch at all.

The overheating isn't necessarily just about the load applied more about actual heat dissipation at the module you could try adding add a Shelly Bypass
 

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