A forced air system is a method of heating or cooling the interior climate of a building. As its name suggests, a forced air system literally forces heated or cooled air into a building, causing the interior temperature to rise or fall as needed. Forced air systems are quite common in many areas, since they provide an effective means of controlling the climate of a building.
At the heart of a forced air system is the furnace and, when so equipped, the air conditioning unit. In buildings with forced air systems, a series of ducts and air registers draw interior air and direct it to the heater or air conditioning unit. As air is drawn into the furnace, it is heated and forced back into the rooms of a building through the use of a blower. While the heating function is operating, the system will continue the process of drawing in cold interior air, heating it at the furnace and blowing the heated air back into the building.
The mechanics of cooling the interior climate of a building is very similar to that of the heating process. Interior air is drawn through the series of ducts and registers to the air conditioning unit. Once the heat is removed from the air, the cooled air is then transported back through the forced air system into the interior of the building.
While there are several different types of air conditioning systems, most systems work by directing warmer interior air over a series of metal fins, pipes or coils containing a refrigerant, such as freon. As the warm air flows through the system, the heat in the air is transferred to the cold refrigerant in the metal fins, pipes or coils. The heated refrigerant is then cycled through the system to enable the heat in it to dissipate, while cooled refrigerant takes its place in the fins, pipes or coils. As with the heating process, the air conditioning process will continue as long as the forced air system is on.
Most forced air systems are operated through the use of a thermostat. In many ways, the thermostat is the brain of a forced air system. In its simplest form, a thermostat enables the user to manually turn the climate control system on or off and also allows the user to predetermine at what temperature the heating or cooling system should automatically turn on or off. Some advanced thermostats provide functionality such as the ability to program the system to turn on and off at specific times of the day and at specific temperatures.