Gas furnaces are one of the most common types of residential heating systems. They work by burning natural gas to create heat. The heat created by a gas furnace is then exposed to a blower, which pushes it through the ductwork. Whether your home currently has a gas furnace, or if you’re thinking about having one installed, you should familiarize yourself with the basic parts of a gas furnace.
All gas furnaces have at least one burner. A burner is a hollow component where combustion takes place. Natural gas and air are mixed together inside of burners where they are burned. By burning these elements gas furnaces create heat.
Some gas furnaces only have a single burner, whereas others have two or more burners. Regardless, all gas furnaces have at least one burner where natural gas and air are mixed together and burned.
The ignitor lives up to its namesake by igniting the natural gas and air mixture inside of the burners. While natural gas is flammable, it still requires some form of ignition for combustion to occur. This is the goal of the ignitor. It provides the flame or heat needed to ignite the natural gas and air mixture inside of the burners.
There are different types of ignitors used in gas furnaces. In the past, most gas furnaces used pilot lights. Pilot lights generate a small flame that ignites the fuel mixture inside of the burners. Newer gas furnaces, on the other hand, often use a hot surface igniter. A hot surface igniter is an electric device that generates heat without actually producing a flame. As electricity flows through the hot surface igniter, it generates heat. This heat will then ignite the natural gas and air mixture inside of the burners.
In addition to one or more burners, gas furnaces have a heat exchanger. The heat exchanger is another hollow component. It doesn’t hold natural gas, though. Instead, the heat exchanger holds combustion gases. Combustion gases are created inside of the burners, after which they enter the bottom part of the heat exchanger. From here, the combustion gases are vented out of a flue pipe.
Heat exchangers contain solid fins above the hollow part. These fins are responsible for absorbing heat from the hot combustion gases. They are made of thermally conductive metal, which allows the fins to absorb heat.