3-way: detect if light is on?

Can a red or black on/off switch in a 3-way circuit detect if the light is on or off even if the dumb side turns it on?

My goal is to be able to turn this one light off after X minutes, but i have to know when the light was turned on at either switch to do that.


Yes it absolutely can. And if you use a Red switch, as well as the light’s on/off status (which will be correct even if you turn the switch on/off from the 3way) you can look at the light power consumption.

Some more detail on this- In a normal 3way setup, you have power come in, then the two sides of the 3way are essentially single pole double throw switches. Power comes in and goes out of the first on either the load or traveler wire, both of which go to the second switch. The second switch connects the lamp to either the load or traveler wire from the first switch. This diagram will make more sense.

In this setup though, up and down don’t matter. But with a smart switch up and down DO matter, and the switch has to be able to (on command) turn the light ON or OFF, not just toggle the state with no clue what that state is.

Thus, the Inovelli switch is a bit smarter. Rather than just sending power to one of two places (which may not go anywhere if the other side isn’t on), the Inovelli switch has one power regulator/switch, a relay to send that controlled power to EITHER Load or Traveler, and circuitry to continually sense the status of the Load and Traveler wires.

The other side of the 3way will connect EITHER load OR traveler to the lamp, the other will be floating / not connected to anything. So the switch continually senses which is which. If that status changes, the switch decides the remote 3way switch has been toggled, and it reacts (by turning the power on/off, and by clicking its own internal relay to send the power to the wire connected to the lamp).

Point is, rather than use the remote 3way to actually interrupt power flow, it just senses the state of the remote 3way and takes that as an input. So, it WILL know if the light is on or not.

That all said, I’d suggest get a 3way companion module (GE/Jasco or HomeSeer), or use a second Inovelli switch paired to the first with a Z-Wave association.

It might. I don’t have any in a 3 way setting, but I use a black series on a bath fan. I use Hubitat to turn off the switch after 20 mins when the switch is turned on. Works likes a champ. I’d imagine the same would be for a 3 way since the switch reports to the hub it was turned on and the counter would begin.