What is the typical flue gas temperature range of a Category III furnace?

The typical flue gas temperature range for a Category III furnace is indeed around 280°F to 300°F. Category III appliances are known for their ability to vent flue gases that are typically more concentrated and include positive pressure in the venting system. This design leads to higher flue gas temperatures compared to other categories of furnaces.

Understanding that the flue gas is under pressure and the materials used in Category III appliances are generally more durable allows for these elevated temperatures. The 280°F to 300°F range is appropriate for efficient operation and effective evacuation of exhaust gases while minimizing condensation within the venting system. This temperature range helps to ensure that any moisture does not condense, which could lead to corrosion or water damage to the venting materials.

In contrast, lower temperature ranges, such as those found in other categories, would not accommodate the same design conditions and operational efficiency associated with Category III systems. Therefore, the 280°F to 300°F range reflects the proper operational parameters for this category of furnace.