Where the vertical vent has a larger diameter than the vent connector, which measurement shall be used to determine the minimum vent capacity?

In scenarios where the vertical vent has a larger diameter than the vent connector, determining the minimum vent capacity requires focusing on the diameter of the vertical vent. The capacity of a vent system is closely related to the area of its cross-section; a larger diameter allows for increased airflow and discharge of combustion products, hence enhancing the system's efficiency.

Using the vertical vent diameter as the basis for determining capacity is critical because it characterizes the fundamental limitation on how much gas can be moved through the system. The vent connector's role is primarily to connect the appliance to the vent and can often have a smaller diameter; however, the vertical vent’s diameter ultimately dictates the maximum potential flow through the system.

Vent connector capacity or vertical connector diameter would not provide a complete and accurate picture in this context, as they could underestimate the overall venting capability if they are smaller than the vertical vent. The vent size ratio is a comparative term, but it doesn’t specify the measurement needed for calculating capacity effectively. Thus, focusing on the vertical vent diameter ensures adherence to safety and efficiency standards in venting systems.