A forced air furnace uses a combination of furnace and ductwork to warm the home. Room air is pulled into the house’s ductwork. It travels through the ductwork to the furnace where the air is heated. Once the air is warmed, it is pushed back into the room. Before the widespread use of forced air furnaces, the most common heating systems were known as gravity furnaces. They used convection, rather than blowers, to move warmed air through the home.
Forced air furnaces can use any type of fuel for heat. The most common type of forced air heating system uses natural gas, but they can also use oil, coal, wood, or electricity. Natural gas, because it is widely available and relatively inexpensive, is an excellent choice for forced air furnace systems.
In these types of heaters a pipe brings natural gas into a combustion chamber which houses a pilot light. A thermostat controls the burner attached to the pilot light. Air from the home is pulled from the ductwork into the combustion chamber. The combustion chamber is a metal box that retains heat. The air is warmed in the combustion chamber and the warmed air moves back into the home. More air is brought in from the ductwork for heating. Exhaust fumes from the combustion process are vented, either through the roof or wall.
Electric forced air furnaces work in the same way as natural gas heaters, but rather than having a pilot light and burners, they use heating elements to warm the air.
Any type of forced air furnace requires ductwork. The ductwork may be made of metal and wrapped in insulation, or made of a flexible material that combines the ductwork with insulation. The insulation is important because it prevents the air from cooling on the trip from the furnace to the room.
There are two types of air registers in a home that uses a forced air furnace. The air returns are larger and there may be only one or two on each level of the home. They pull air from the rooms and send it to the furnace. The room registers are smaller, and there will be one or two, or even more, in each room. They deliver the warm air into the home.
There are several things that you can do to increase the output of your high efficiency furnace. The room registers should be evenly distributed through the home. If some areas of the home are perpetually warmer than others, consider partially or completely closing the room registers in those areas. That allows more warmed air to flow to other areas of the home. Also, do not block the air returns with furniture. For the most efficient exchange of air, the air returns should be unobstructed.
No matter what type of forced air system you have, there are several additions that you can make to your heating system that will improve your home’s comfort level. You can add air conditioning units, humidifiers or air filters to your system to cool your home in the summer, add moisture to the air or clean the air in your home.