How a Furnace Works

The furnace is not a new invention. While in earlier times it was simply a wood stove used for both cooking and heating the home, early versions of the furnace used coal, wood, or oil to spread heat throughout the house using ducts to distribute hot air from room to room.

Today’s furnaces are primarily gas, although there are electric, wood, and propane furnaces available depending both on how rural the geographical area of the home is and on what type of energy is easiest and cheapest to access. Gas furnaces burn cleanly and are affordable.

When the thermostat recognizes that the room is getting too cold for the preferred temperature setting, it triggers the pilot light to ignite a burner located in the combustion chamber. This is where the heat is concentrated. And from there it moves into the heat exchanger, which is a metal chamber that heats up the air circulating past it.

The newly heated air then flows into the hot-air plenum and from there to the ducts that disperse the heat through all the rooms of the house. The gases created by the combustion are released either through the wall or a flue on the roof.

The ductwork is made of metal and wrapped in insulation to keep heat and cold from escaping before it enters the rooms it is intended for. When the furnace is part of a forced air system, a Heating Ventilating and Air Conditioning system (HVAC), the air conditioner can utilize the same ducts for delivering cool air to all the rooms in the summer.

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