How is the area of vent lines calculated when manifolded?

The area of vent lines when manifolded is calculated by taking the largest vent area and adding half of the combined additional areas from the other vent lines. This method ensures that the venting capacity is sufficient for the overall system by accounting for the different sizes of the vent lines and optimizing the flow characteristics.

Using the largest vent line in combination with half of the areas of the smaller lines helps to balance the system and ensures that there is minimal resistance to airflow. This approach is necessary because as multiple lines are combined or manifolded, the overall venting performance can be impacted by the diameter differences among the lines. This calculation is crucial to prevent pressure buildup and ensure efficient exhaust of gases, thus adhering to safety standards.

Calculating only the area of the smallest line would not provide an accurate representation of the system's capability to vent properly, while averaging might overlook the need to prioritize the largest opening for optimal flow. Hence, the correct method combines the largest area with a portion of the smaller areas to achieve maximum efficiency and safety in operation.