My power went out recently, and while we were waiting for it to come back on, I switched on the gas fireplace. In that instant I was sure it wasn’t going to work, but lo and behold, the fireplace came on. And I was able to turn it off and on at will.
Does a fireplace switch not use electricity? I had been thinking of replacing it with a smart switch so I could just yell at the fireplace to turn on, but if it’s a “special” switch, I might have to re-think that.
Your switch is either mechanical and has a sparker or uses a battery it sounds like to me.
It must have a pilot light. Similar to my water heater (which does not use electricity), there is always a small flame ready to ignite the gas.
You have what is called a millivolt system. If look at the pilot light you will see that the flame is engulfing a small metal stub that might even be glowing red hot. That stub is called a thermopile and converts heat to electricity - in this case a few hundred millivolts DC. This voltage from the thermopile runs to your wall switch, then from the wall switch back to the gas valve in the fireplace. When you close the switch, that voltage generated by the thermopile opens the gas valve and the fireplace lights.
This is a fail-safe system - the valve can only open if the thermopile is generating voltage. The thermopile only generates voltage when heated by the pilot light. Therefore the valve cannot open if the pilot light is out.
ETA: In case it wasn’t clear from my description, the wall switch that controls the fireplace is not connected to power in the house. Just replacing it with a smart switch will not work. There is likely a solution out there - RF remote controls for millivolt fireplaces are pretty common.
There are millivolt thermostats available, too, if you wish to control your fireplace with a thermostat rather than a switch.
Gravity furnaces and boilers were often millivolt systems (or were converted from coal to gas millivolt systems), as the heat would work whether or not the power was on.
Thanks, I’ll look into an RF or IR solution.