Getting to Know Your Gas Furnace – What Happened to the Pilot Light?

When cold weather begins, more Americans use gas furnaces than any other type of heating system. Hopefully, your local HVAC service has checked everything out and cleaned your furnace, so starting up will not be a problem. Not long ago, most people went into the basement (or area where the furnace was located) to turn on the heat. To start the heat, you turned on the gas and lit the furnace pilot light. However, modern furnaces do not have pilot lights. Where did they go?

To better understand what happened to the pilot light, you should know how it works. A pilot light is a small flame located close to a gas burner. The flame stays lit all the time, and when gas reaches the burner, the pilot light ignites the gas. But what happens if the light goes out for some reason?

A sudden wind storm or air in the gas lines may extinguish a pilot light. However, it has a safety feature called a “thermocouple” probe. The probe is made from two dissimilar metals and when you apply heat to them, it creates an electric current. The thermocouple is right next to the pilot light and heat from the flame keeps the current flowing to an electromagnetic gas valve. As long as the valve gets power from the thermocouple, it stays open and keeps gas flowing. If the pilot light goes out, electricity no longer flows to the gas valve and it shuts off the gas to the furnace burner.

Pilot lights may go out without notice and if it happens in the middle of the night, you could wake up without any heat. Although not common in Southern California, in colder climates if your pilot light goes out, your pipes can freeze and burst from lack of heat. Pilot lights use gas constantly and may consume as much as four to five dollars worth of gas each month.

Pilot lights are being replaced by electronic ignitions. How do these work? When the thermostat calls for heat from the furnace, it sends power to a small device which gets red hot. Some igniter systems use an electrically generated spark to light the furnace burners. Electronic ignitions are more efficient than pilot lights because they only use energy when needed. They seldom fail and give you years of trouble-free service.

For more information on how your gas furnace works and how to solve heat problems, talk to your local HVAC company.