I don’t have an answer for you, but this is a clever idea. I also have a gas fireplace with a switch. I may have to look in the box and see what’s there.
The switch for my fireplace is on the side of the metal border around it. This is just a simple circuit. When switched on it turns on the fireplace, when off it breaks the loop and the fireplace goes off.
I wired up a Remotec relay to an old power cord and plugged it into the outlet behind the gas fireplace that also provides power to the fan. Then the wires from the switch go to the “external” hook up on the relay, and the relay circuit runs to where the switch used to be.
Now I can use SmartThings to turn on/off the fireplace. But the external switch still works too.
I’m not a electric wizard by any means, but I have the same issue. Can someone link me to a “relay” that would work? this is what my current fireplace control looks like. Would like to simply add a GE on/off switch. Please see pic. Possible?
I had been fighting with this issue…I’m currently using a CT100 thermostat, it is both battery powered and low voltage powered. I connected the fireplace switch which is open or closed to the “heat” and R terminal. I can turn the fireplace on/off by changing the mode. An issue that I haven’t resolved (certainly open to suggestions) is “heat” and “auto” are fireplace ON…“off” and “cool” are fireplace OFF. The CT100 mounted over existing switch box for a clean installation.