In a Category IV two-pipe vent system that terminates through the roof, the elbow for the combustion air intake should be pointed in which direction?

In a Category IV two-pipe vent system, the elbow for the combustion air intake should be pointed downward. This orientation is important for ensuring proper drainage of any condensation that may form within the piping. Category IV systems typically operate at low flue gas temperatures, which makes them susceptible to condensation. By directing the elbow downward, any moisture that accumulates can effectively drain away from the intake, preventing blockage and ensuring a consistent supply of combustion air.

Additionally, this design minimizes the risk of outdoor debris entering the intake and obstructing airflow. It also helps maintain a reliable air supply, which is essential for efficient combustion and overall system performance. Properly directing the intake contributes to the safety and reliability of the heating system, thereby enhancing its overall efficiency and longevity.