The typical flue gas temperature of a Category III furnace is:

The typical flue gas temperature of a Category III furnace is understood to be in the range of 280°F to 300°F. Category III appliances are often classified as positive pressure systems that vent flue gases through a separate exhaust system. This classification results in higher flue gas temperatures compared to other categories, primarily because they are usually designed to operate with a lower efficiency and do not condense the flue gases.

Flue gas temperatures in this range are important as they help ensure the proper functioning of the furnace and maintain safety standards. By operating within this temperature spectrum, the furnace can effectively vent gases without the risk of condensation inside the flue, which could lead to corrosion and other issues. Understanding this temperature range is crucial for anyone involved in the installation, maintenance, or assessment of gas furnaces, as it connects directly to the efficiency and longevity of the appliance.