PrintMost furnaces are gas-fired, but other fuels include oil, coal, wood, and electricity.
With a conventional furnace, natural gas is piped to a burner located inside a combustion chamber. There, the gas is mixed with air, then ignited by a pilot light, a spark, or a similar device controlled by a thermostat. The flame heats up a metal box—the heat exchanger—where room air is heated as it flows through. Exhaust gases given off by burners vent outside through a flue that goes up through the roof or, with newer high-efficiency models, out through a wall.
Instructions: Press the play button to see how a gas furnace works, and then answer the question that follows.
Click here to open a text description of how a gas furnace works
How a Gas Furnace Works
In a gas furnace, cold air is pulled into the return register and is heated by the heat exchanger; a series of gas burners within a combustion chamber. The hot air is pushed out and distributed through the house. Exhaust from the gas burners exits the building through an exhaust vent.
An electric furnace uses heating elements rather than burners to heat in the heat exchanger.
Instructions: Press the "play" button to see how an electrical furnace works, and then answer the question that follows.
Click here to open a text description of how an electrical furnace works
How an Electric Furnace Works
A motor-driven fan pulls air into the return register. The air passes through a filter and moves past electric heating elements. The now warm air is pushed out the system and distributed throughout the house.