Learn how and when to remove this message) A furnace (American English), referred to as a heater or boiler in British English, is an appliance used to generate heat for all or part of a building. Furnaces work by heating air or metal using a variety of methods, including combustion, induction, or resistance heating. The heated air or metal is then distributed throughout a home or used in industrial processes.
How a furnace heats air
Fuel, such as propane or natural gas, is burned in a burner
The heat from the burner passes through a heat exchanger
Air from the home’s ductwork is blown over the heat exchanger
The heated air is forced into the supply ductwork
The heated air is distributed throughout the home
How a furnace heats metal
Alternating current passes through a furnace coil
The coil generates a magnetic field
The magnetic field induces eddy currents in the conductive material inside the furnace
The material heats up and melts
How a furnace is controlled
Furnaces can be equipped with automatic control and monitoring systems to precisely control the temperature and time of the heating process.