Posted: February 27, 2019
If you have an older gas furnace, your heating unit relies on a little blue flame known as a pilot light to ensure ignition of the burners. Water heaters, gas fireplaces and old gas stoves also often have similar pilot lights. If your furnace has a round knob on the gas valve with the words OFF/ON/PILOT, you have what’s known as a standing pilot ignition.
As you probably know from experience, the biggest drawback to pilot lights is that they will get extinguished at times, causing you to lose your heat. Common reasons include a nearby draft, dirt buildup, or a malfunctioning thermocouple.
Another pilot light drawback is energy waste. Since the pilot light needs to remain active, your furnace is always consuming some gas. It’s not a lot—usually just a few therms of gas a month—but that obviously adds up over time.
There is a safety issue as well. Pilot lights can develop problems that cause them to burn inefficiently. When this happens, a small amount of carbon monoxide can be released into your home.
All of these problems are not an issue when you have a modern furnace, which uses electronic ignition instead of an old-fashioned pilot light.
Most furnaces with electronic ignition have a device called a hot surface igniter. This is a small electronic device that receives an electrical current whenever your thermostat calls for heat. The ignition heats up to a temperature that is hot enough to ignite the gas to your burners, and then it shuts off after it has done its job.
Another type of electronic ignition is an intermittent pilot light. It uses a small flame to ignite the burners just like a conventional pilot light. The difference is that the flame is only lit (by an electronic spark) when your furnace is ready for a heating cycle. When the pilot light is not needed, it is completely off, saving you money on gas.