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What is a Furnace or Boiler Ignitor?

furnace ignitor

An ignitor, in a sense, is the catalyst that turns your furnace’s or boiler’s fuel into heat. Your ignitor lights the burner, which creates the heat within the heat exchanger. But how does the ignitor itself work?

Types of Ignitors

In the past, most furnaces and boilers used pilot lights to provide the flame that would ignite the gas released by the burners, starting the heating process. The pilot light is a standing flame that burns by maintaining a constant link to a small flow of gas. When your furnace or boiler switches on, a valve releases a larger flow of gas into the burner and that fuel is then lit by the pilot light, generating heat. To prevent safety issues in the event that your pilot light goes out, a small valve is installed that shuts off the flow of any gas when the flame dies down.

Today, you’ll find that most furnaces use electric hot surface ignitors. Experts state that this is because this system is not only more dependable, it is more inexpensive to make and use, since it doesn’t require a steady stream of fuel the way the pilot light does. The hot surface ignitor is a thin wire that, upon receiving an electrical signal, glows red hot and creates a spark that sets off the heating process. In order to create—and withstand—a hot enough spark, manufacturers often use wires made of the high-heat-resistant materials silicon carbide or silicon nitride.


On occasion, your pilot light may go out as a result of drafts, requiring you to manually relight it. Dirty or broken sensors or thermocouples are other fairly common causes of an unlit pilot light.

Electric hot surface ignitors, on the other hand, have a definite shelf life. Although it may take as long as five years, your ignitor will eventually burn out. Regularly cleaning your furnace’s filters and gently cleaning around the ignitor may extend the life of this component, although you should keep in mind that handling can easily damage the fragile wire. Replacement ignitors available from wholesalers or online retailers can cost anywhere between $17 and $77, depending on the needs of your furnace or boiler. To replace the ignitor yourself, consult your furnace’s or boiler’s user’s manual, or contact your HVAC maintenance technician to do the job for you.

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