A gas furnace with an induced draft blower is classified as which category by the National Fuel Gas Code?

A gas furnace with an induced draft blower is classified as Category III by the National Fuel Gas Code. This classification is based on its exhaust characteristics and the design of the venting system. Category III appliances are designed to vent products of combustion with a positive vent pressure, which is facilitated by the induced draft blower. This blower helps to push the flue gases out of the furnace and through the venting system.

Additionally, Category III appliances typically have a cooled venting system, which allows for the use of metal venting materials. The combustion products can be at higher temperatures, and the system is designed to handle these conditions safely. This classification is essential as it informs installation practices, maintenance protocols, and safety requirements necessary to operate the furnace correctly and efficiently.

Being aware of the specific category also helps in distinguishing these systems from others, such as Category I, which encompasses naturally vented appliances, and Category IV, which refers to appliances that operate at low temperatures with the use of plastic venting due to their condensing nature. Understanding these distinctions is important for safe handling and compliance with regulations regarding gas appliances.