How Does a Switch-Activated, Gas Fireplace Work Without Electricity?

[Pat Germain]

My house has a gas fireplace insert. It has a pilot light, but is activated by a "light switch" on the wall. I assumed the fireplace would not work without electricity.

But sure enough, my whole neighborhood lost power and my wife asked me to turn on the fireplace. I told her it wouldn't work, but tried anyway and hit the switch. "Whoompf!" the fireplace roared to life.

My fireplace has no batteries of any kind anywhere. How does that work? Right now I'm going with "magic".

[Rod Sheridan]

Pat, your fireplace would have a thermocouple and a Milli-volt gas valve.

When the thermocouple is heated by the pilot light, it generates a very small electrical voltage (millivolts) which can be run through a switch to turn on a Milli-volt gas valve (as opposed to a 24 volt gas valve used with a conventional thermostat).

Regards, Rod.

[Pat Germain]

Well, there you go. Mystery solved. Thanks, Rod!

[Jim Finn]

Pat, your fireplace would have a thermocouple and a Milli-volt gas valve.

When the thermocouple is heated by the pilot light, it generates a very small electrical voltage (millivolts) which can be run through a switch to turn on a Milli-volt gas valve (as opposed to a 24 volt gas valve used with a conventional thermostat).

Regards, Rod.
These"Thermocouples" were common in the 50's. We called them "Powerpiles"

[Dave Beauchesne]

These"Thermocouples" were common in the 50's. We called them "Powerpiles"

Jim is correct - there will be a ' powerpile ' that supplies the power for the gas valve - a typical powerpile produces .75 volts, enough for the task.

A typical ' thermocouple ' like is used on a standard efficiency furnace, produces about 25 - 30 millivolts ( .025 volts ) .

Dave Beauchesne