How Do Forced Air Furnaces Work?
Basics A forced air furnace pulls cold air into ductwork that runs throughout your home to the furnace to be heated. When the air is heated, it travels back through other ductwork and forced out through heat registers, warming rooms. Fuel Several types of fuel can be used to heat the air, including oil, coal, wood, electricity or gas. Most forced air systems use natural gas, because it is considered to be the least expensive option and is widely available. A natural gas system moves fuel through a pipe from the supplier into a combustion chamber, which has a pilot light for igniting gas being fed to a burner. A thermostat that senses temperature and usually is mounted on a wall in a living space controls the supply of gas to the burner. The thermostat is set to maintain a desired temperature, and when the air temperature falls below the setting, it supplies more gas to the burner, which then heats the air that has been drawn into the combustion chamber. The thermostat also activates a
