Appliances that use natural gas for fuel, like your furnace, water heater or clothes dryer, rely on combustion to create heat. These appliances have traditionally utilized atmospheric combustion, or from air drawn inside the home, often from the basement. The combustion exhaust gases are then vented out of the flue or chimney. With sealed combustion appliances the supply and return air flow is tightly contained, so it does not have to rely on the air inside the home to convert fuel into heat.
The Advantages of Sealed Combustion
The main advantage of sealed combustion is improved efficiency. To achieve an Annual Fuel Utilization Efficiency (AFUE) of 90 or higher, furnaces utilize sealed combustion. With sealed combustion, the furnace connects to the outdoor air through a supply and a return pipe. Because the air supplied to the furnace is outdoor air, and the flue gases are exhausted back outside furnace efficiency is increased because it is not heating air only to vent it outside.
Another advantage of sealed combustion is safety. Without an exposed flame, there is no risk of flammable materials near the appliance catching fire. Burning natural gas can also generate dangerous carbon monoxide (CO) gas, which is more likely to enter the home through backdraft in an sealed combustion chamber.