A home furnace is a major appliance that is permanently attached to the abode to provide heat to an interior space through the circulation of hot air throughout the building. The most common energy source for modern combustion furnaces in America is natural gas; other frequently used energy sources include propane (LP), fuel oil, coal or wood. In certain cases electric resistance heating is the chosen source of heat, especially where the cost of electricity is low. Combustion furnaces of necessity must be vented to the outside. Traditionally, this is through a flue, which expels hot air along with the exhaust. Central Warm-Air Furnace: A central hot-air furnace is a form of space-heating appliance in which a central combustor or resistance unit--generally using gas, fuel oil, or electricity--provides hot air that circulates through ducts leading to the various rooms. A forced-air furnace is one in which a fan is used to force the air to flow through the ducts. In a gravity furnace, air is circulated by gravity, depending on the natural flow of warm air up and cold air down; the warm air rises through the duct system and the cold air falls down through ducts, which convey it back to the furnace where it is reheated, thus concluding the revolution cycle.The furnace is generally is divided into three primary components: The burner (consists of heat exchanger, draft inducer and venting) - The flame is created by the burners and is subsequently drawn into the heat exchanger by the negative pressure created by the draft inducer. The hot gasses produced by the oxidation of the flame travel through the chambers of the heat exchanger and heat the metal walls of the heat exchanger. The gasses cool as they give off their heat to the heat exchanger and are at about 120 degrees as they exit a high efficiency furnace. The cooled gasses then pass into the draft inducer blower, which pushes them into the venting pipes. The exhaust gasses then are directed out the house via the vent pipes. The blower and air movement - The blower creates a negative pressure on the intake side which sucks air into the ductwork return air system and ejects the air out across the heat exchanger and then into supply air ducts for distribution throughout the home. Controls and Safety Devices -Furnace controls consist of a gas valve, ignition control, ignitor, flame sensor, transformer, limit control, blower control board, and flame roll out switch. A limit control is a safety apparatus that will turn off the electrical circuit to the ignition control and stop the gas flow if the furnace overheats. The flame roll out switch does the same thing if the flame should roll out of the heat exchanger instead of being completely induced into it by the draft inducer.
The furnace is an admirable appliance, whose multiple components ensure that you and many other householders will sleep in warm comfort throughout the cold winter season.
