When structural steel columns are utilized as downleads, how often must they be grounded?

Using structural steel columns as downleads in lightning protection systems requires proper grounding to ensure the effectiveness of the system. The best practice is to ground these columns every other column, while averaging no more than 60 feet between grounding points. This helps to provide a low-resistance path for lightning currents to dissipate safely into the ground, ensuring both safety and compliance with applicable standards.

Grounding at every other column facilitates consistent grounding throughout the structure while preventing excessive grounding conductors that might lead to increased resistance and potential lightning damage. If grounding were done at only one every 100 feet or less frequently, the risk of inadequate grounding performance increases, especially in larger structures where lightning might strike multiple locations. Additionally, the 20-foot threshold mentioned does not align with the best practices set forth in lightning protection guidelines. Regular, systematic grounding actions, such as those undertaken every other column, are critical for effective lightning protection design and implementation.