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

techno79

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
Ah okay, yeah I guess could go with using just normal toggle switch and then just dim from the mobile app (not as neat but doable).

Is there a way to set the max brightness for a Shelly Dimmer? To be honest, the spotlights at 80% are pretty bright and that could help get around the overheat alerts.
 

Seb Briggs

Distinguished Member
You could also use a momentary switch. Single click on , single click off, press and hold dim up press and hold again dim down .

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There is no maximum brightness setting though I do know its been asked for many times so possibly in a future firmware update
 

techno79

Member
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.

I think there must be something wrong. I was getting overheat warnings even when it was set to less than 50% brightness. The Shelly Cloud app was telling me there was less 20 watts being drawn. I've got other Shelly devices installed in other areas that draw more wattage than that without any issues. Not sure if this is an indication of a faulty Shelly Dimmer or if the wiring is wrong in anyway. Has anyone else come across similar issue and what the resolution was for this?
 

techno79

Member
As I mentioned before overheating doesn’t have to be anything to do with power draw
Ah okay, sorry I missed your previous comment about overheating. All the Shelly devices have been put into protective enclosures (the same type) so it odd that it would be affecting just the one Shelly when they're all in the same type of enclosure.

Anyway, my electrician this morning has swapped out the Shelly Dimmer for an alternate one in case it might have been a faulty Shelly and they've put some vent holes in the enclosure to help with heat dissipation (although the other Shelly's don't have this).

The electrician has now gone but I've just tested this and it's still overheating. I will reach out to Shelly support to see if they can help but not sure what else to try.
 

Seb Briggs

Distinguished Member
Certainly sounds like that a mixture of the position and possibly (don’t quote me as I’m not an electrician ) that the wiring is leading to overheating.

I had a similar issue and it was because it was in a tight space but also next to a few other none Shelly switches . Just too hot
 

techno79

Member
Certainly sounds like that a mixture of the position and possibly (don’t quote me as I’m not an electrician ) that the wiring is leading to overheating.

I had a similar issue and it was because it was in a tight space but also next to a few other none Shelly switches . Just too hot
I did some Googling on their support forum (Forum - Offizielles Shelly Support Forum) and quite a few others have the same issue. Doesn't seem to be any conclusive fix for this. Some users mention about changing the settings for the Shelly from Leading Edge to Trailing Edge and doing the calibrating (both of which I've done) but this hasn't helped.
 

techno79

Member
Try adding a Shelly bypass not supposed to be needed for circuit with neutral but worth a go
Just for my own understanding: in layperson terms, what does a Shelly Bypass actually do and how would it help with this issue?

Do you have a wiring diagram for how that links up? Something an electrician can work out how to install?
 

Seb Briggs

Distinguished Member
It’s a dummy load that regulates the load on the module
 

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techno79

Member
It’s a dummy load that regulates the load on the module

Ah thank you. So is the Shelly Bypass something that will appear as a WiFi device that I need to setup in the Shelly Mobile app or it's a dumb device that just works off the electrical cabling?

Also, is the wiring of the Bypass the same even in my situation as the setup is slightly different:
  1. I have a single light switch
  2. Shelly Dimmer is connected at the spotlight (so it is connected with neutral)
  3. The light switch is a 2 way retractive centre off one
Thanks again
 

techno79

Member
Sorry, just coming back to this as I was abroad for a few weeks. So the problematic Shelly Dimmer is installed at the spotlight and it is connected to a single switch (a momentary 2 way retractive, centre off type).

How should the Shelly Bypass connect in this setup?
 

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