Furnace
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A household furnace is a major appliance that is permanently installed to provide heat to an interior space through intermediary fluid movement, which may be air, steam, or hot water. The most common fuel source for modern furnaces in the United States is natural gas; other common fuel sources include LPG (liquefied petroleum gas), fuel oil, coal or wood. In some cases electrical resistance heating is used as the source of heat, especially where the cost of electricity is low.Air Distribution System
Air distribution.Crossover Igniter
Most furnaces have more than one burner. One pilot flame usually ignites all the burners. A crossover igniter is used to bridge the flame from one burner to the next.Heat Exchanger
The main component of heating units, both forced air and hot water, is the heat exchanger. This component takes the heat produced by burning fuel and transfers it to the air for distribution throughout the house.