How a Furnace Gas Valve Works

Just over 50 percent of American homes now heat with natural gas-fired furnaces.

Adding Fuel to the Flame

Hands removing the control panel of a gas furnace.Hands removing the control panel of a gas furnace.
The heart of the furnace is the gas valve that regulates the flow of natural gas to the burner. A standard valve includes a rotating control dial, as well as a pilot light reset button. In addition to regulating burner gas, the valve supplies gas to the pilot light as well as connects to the thermocouple that automatically shuts off the gas if the pilot goes out. High-efficiency furnaces that utilize an electronic igniter instead of a standing pilot light do not incorporate a manual lighting procedure, and the gas valve typically provides only a basic on/off control.

On standard or electronic units, when the valve control dial setting is “Off,” gas to the burner is shut off. On a conventional pilot light furnace, rotating the dial to the center “Pilot” setting and depressing the pilot reset button allows the pilot light to be manually lit. When the dial is rotated to “On,” the valve supplies gas to the furnace burner when the thermostat signals for heat. If the furnace utilizes an electronic igniter, an ignition control module receives the thermostat signal, energizes the igniter, then automatically opens the valve and gas flows to the burner.

About the Author

Gus Stephens has written about aviation, automotive and home technology for 15 years. His articles have appeared in major print outlets such as "Popular Mechanics" and "Invention & Technology." Along the way, Gus earned a Bachelor of Arts in communications. If it flies, drives or just sits on your desk and blinks, he's probably fixed it.