How Does a Gas Pilot Light Work?

Updated April 17, 2017

Water heaters, hobs, ovens and furnaces are all gas appliances that often make use of a pilot light. A pilot light is a small flame that burns continuously. When the appliance operates, the pilot light serves as an ignition source for the main gas burner in the appliance. Over the past 20 years the use of pilot lights has fallen and very few new appliances are equipped with them. New appliances use a spark to ignite the main volume of fuel. Pilot lights are still used in millions of existing appliances, however, and understanding how they work can simplify daily life.


Pilot lights are valves that allow a very small amount of gas to pass through them. This gas is lighted and a small flame burns continuously. This flame is located near the main burner of the appliance. When the appliance is turned on, the pilot light ignites the flame in the main burner, allowing the appliance to work as designed. Nearly all pilot lights operate in this manner.


Sometimes new homeowners or renters of new apartments are unable to determine if the appliances located in their new home are operated with a pilot light or another ignition source. Determine if a pilot light operates an appliance by looking at the on/off switch near the gas source. This switch will usually have a "pilot" position if the appliance is operated with a pilot light. Additionally, the owner of the gas appliance can open the access panel to the gas burner area. When this panel is open, a small flame is usually visible if the appliance uses a pilot light.


Pilot lights have both positive and negative effects. Pilot lights do not require electricity to operate the appliance. Gas appliances that work with pilot lights will usually operate during power outages. Pilot lights also offer nearly instant ignition of a main burner. Since the pilot light always is burning, an ignition source is immediately available whenever the owner desires to operate the appliance. While operating continuously gives instant ignition, it also wastes gas. Pilot lights use approximately 20 per cent of the gas consumed in the United States annually.


Pilot lights are designed to operate safely. At first glance, it would appear that pilot lights are dangerous because they are continuously lit. However, the small amount of gas used in a pilot light ensures the pilot light flame is extremely small and safe for a home. Additionally, safeguards exist to make sure the gas source is extinguished if the flame blows out for any reason. Pilot lights have a device called a thermocouple. A thermocouple produces electricity from heat. While the thermocouple is heated from the pilot light, electricity is transmitted to a small valve that allows gas to pass through. If the pilot light is extinguished for any reason, the thermocouple will stop producing electricity and the valve will close. This will stop gas from flowing into the home.


Occasionally pilot lights need to be lit. Sometimes a draft will extinguish a pilot light. Other times the gas source will be interrupted to the pilot light and it will be extinguished. No matter the reason, lighting a pilot light is an easy process. First, locate the gas control knob.This is usually at the bottom or the rear of the appliance. Then, open the access panel near the knob. Turn the gas control knob to the "pilot" position. Press the knob and use a match to light the pilot light. Keep the knob depressed for 30 seconds while the flame heats the thermocouple. After 30 seconds, turn the gas control knob to the "on" position.

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