In a natural draft furnace, what is the typical vent stack temperature?

In a natural draft furnace, the typical vent stack temperature is generally in the range of 450°F to 550°F. This temperature range is necessary because natural draft systems rely on the buoyancy of hot gases to create a draft that carries combustion products from the furnace to the exterior. The gases must be sufficiently hot to rise effectively and maintain the proper draft, ensuring effective venting and preventing the buildup of harmful gases within the living space.

Gas combustion generates heat, and as the temperature of the exhaust gases drops, their ability to rise diminishes, which could compromise the efficiency of the venting system. Operating within the provided temperature range helps to maintain the necessary upward draft and prevents issues such as condensation, which can occur if the exhaust temperature is too low. This context is essential to understanding why the specified temperature range is typical for natural draft systems.

The other options represent temperatures that are either too low or too high for effective operation in typical residential systems, which could indicate potential problems with efficiency or safety.