I purchased a Sonoff ZBMINIL2 to transform a 2-way switch setup into a smart switch for integration with Home Assistant. These two 2-way switches control a standard ceiling light.

Following a discussion I found, I wired the second switch according to diagram A. wiring diagram A
The common terminal of the second switch is connected to the S2 on the smart switch, another live wire from the junction box is connected to the L in, and the wire that was previously the common is now on the L out.

However, I'm encountering a problem: the moment I turn on the power, it triggers the circuit breaker. If I remove the smart switch and revert the wiring to its original state, everything works fine.

When I measure the voltage, I see power at the common terminal of the first switch, and if I disconnect the common from the second switch, I see power on one of the two traveler wires, depending on the switch position.

My other hypothesis was that my light might be mounted on the live wire, as shown in diagram B. wiring diagram B

Is this a possibility? Can I integrate the ZBMINI in this configuration, IF this is indeed the setup I have?

  • Are you 100% certain that the Sonoff will work with other multi-way switches? I've confirmed that my Shelly relays are not designed to do so. Also, let me introduce you to Internet of Things, which would probably be a better fit, and let you know that HA has a Discord server where you'd probably get much better help.
    – FreeMan
    Feb 21 at 11:39

1 Answer 1


The wiring is incorrect. The switch does not go to Live, it goes from S1 to S2.

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Do what you have, but take the end of the switch chain back to S1


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