I have 2 Sonoff Mini R2's installed as a part of some remodeling work I'm doing on my house:

sonoff mini r2

What I love about these devices is that they allow you to turn any dumb toggle switch (what Sonoff refers to in their doc as an "SPDT switch"). I like this for 2 reasons:

  1. My wife and I love vintage aesthetics and want to stay as true as we can to the original aesthetic of our home built in 1920, so using a regular toggle is truer to that aesthetic.
  2. It's easier to flip a toggle switch without looking at it (than a decora style switch) and you know from its tactile and audible feedback that it was successfully toggled.

HOWEVER - I found out in my electrical inspection today that Sonoff devices are not UL rated/certified - and for me to pass the electrical inspection, I have to remove them.

I know that there are smart switches out there that mimmic a "toggle-style" switch. They stick straight out and don't have the same tactile experience. Such a switch is what I will fall back to if I cannot find what I'm looking for.

So is there a device like the Sonoff Mini R2 that:

  • Is small enough to fit in a switch box
  • Has an "SPDT" switch circuit
  • Is UL rated/certified?

Note, the one drawback of the Sonoff Mini R2 (aside from its lack of UL certification) is that it doesn't report (/"push") when the SPDT switch is toggled, which forced me to implement a polling strategy to catch physical switch flip events and act on them for my automations.

Incidentally, I can tell why these devices don't have a UL rating. I had a heck of a time connecting my 12 gauge wires to them without them popping out. The wires for my second device as threaded 12-gauge and that seemed nearly impossible to connect securely.

  • 1
    Looks like the Shelly 1 is UL certified. Not sure whether there's something like the Sonoff "DIY mode" though. They're description/doc is not terribly straightforward. shelly.cloud/documents/catalogues/catalogue_usa.pdf
    – hepcat72
    Nov 6, 2021 at 2:28
  • Not Wi-Fi but rather Zigbee-based, there's the Philips Hue Wall Switch module which sits in a wall box being the regular switch and is controlled by it. Designed for regular on/off switches (SPST) rather than toggle (SPDT), but I'm not sure why it couldn't work in that case, just connect two of the three terminals. No mention of UL certification, but it's not actually connected to mains.
    – jcaron
    Nov 6, 2021 at 12:52
  • The Zooz ZEN51 is like the sonoff, but on z-wave (not zigbee) and is UL listed (canada/US). The shelly 1 and shelly 2.5 have versions that are UL certified, and those are on wifi. All support different of button modes like "momentary", or "detached", which let you invoke triggers when you flip the physical switch, without turning on/off electricity to the load (e.g. to have a smart bulb always powered on, but having the switch turn off the bulb via an event hook). I know that the zooz supports different forms of 3-way wirings, and I think the shellies also.
    – init_js
    Oct 19, 2022 at 4:44

1 Answer 1


I recently dug into the Shelly switches and installed my first. Most are UL certified, the 1 in particular.

The most "heavy duty" of the Shelly switches only support up to a 16 amp load, so they need to be protected by a 15A breaker, and, therefore, can be installed on 14AWG wiring. Unfortunately, they will not take 12AWG wire (as I learned the hard way). You can, however, pigtail from #12 to #14 in the box where you're installing it (so long as there's a 15A breaker in there; if it's a 20A breaker, you're out of luck either way). On the bright side, you don't need 20A to protect lighting circuits, as you'd be hard pressed (especially if you're using LEDs) to get anywhere close to a 20A load for your whole house full of lights, and most houses don't have all lighting on one circuit.

I'm not sure what the Sonoff "DIY mode" is (as mentioned in you comment), but I have mine connected to Home Assistant, not connected to the internet and have never installed the Shelly app on my phone, so they're pretty much stand alone. Once powered up, it exposes its config via a self-hosted web page where you can then configure it to use your home's WiFi, turn on internet access (mine was off by default), etc.

In the config, you can set the switch to "edge" mode which effectively turns the Shelly & the physical switch it's connected to into a 3-way pair. A toggle of either will toggle the lights. There are other modes, so if you want "up" = "on" on the physical switch, you can select the proper mode and you may have to toggle the physical switch to get the current light status and switch direction into sync before the switch will cause action on the lights it's attached to. I think this addresses your push/polling question.

No, I'm not a Shelly sales rep. I spent more than a week reading up on them and found a YouTube channel with a guy who did a really nice job of explaining at a 1st grade level the differences between the different Shelly models and (in his linked blog) showed exactly how to wire each of the different relays, because Shelly's own documentation is not very clear. I'm just a happy user.

Oh, one last thing. When you finalize your wiring, make sure that you don't have any bare copper sticking out of the device like that! That's just asking for a fire-starting arc to happen between the two hot wires. For the Shellys, you do not have to strip very much insulation off, and it looks like it's the same for the Sonoff. Snip the ends of the wires a bit to ensure the insulation butts up against the device housing.

  • Well, I have a 20A breaker that the circuit is on, and 12 gauge wire... (is that what "AWG" refers to?). I can switch out the 20A breaker for a 15, but that could cause problems? It's the same circuit as the bathroom outlets, which we sometimes have a space heater and (briefly) a hairdryer on... I'll have to think this over. Great answer BTW!
    – hepcat72
    Nov 16, 2021 at 19:44
  • AWG = "American Wire Gauge" so yes, 12 gauge = 12 AWG = #12. ;) You shouldn't have any problem running a space heater on a 15A breaker, though you'd have to read the label on it. If you're not sure, go ask at Home Improvement - loads of real electricians there - they can interpret the label and tell you for certain. If you swap the 20A breaker for a 15A, then yes, you can just pig-tail some #14 wire to the #12 in the wall and connect that to the Shelly - it's what I had to do. And thanks, I've managed to combine a lot of random skills and reading. ;)
    – FreeMan
    Nov 16, 2021 at 20:43
  • The shelly 1 comes in two versions, UL and non-UL listed. The difference is that the UL version has a 15A rating vs 16A for the non-UL. No other difference. The shelly 2.5 also comes in UL and non-UL versions. This one is smaller than the Shelly 1, and can power two 10A-max circuits (which is good for a multi-gang box). I don't know if they support 12gauge though.
    – init_js
    Oct 19, 2022 at 4:40

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