Lightning protection system ground terminals _____ be bonded to the building or structure grounding electrode system.

• A. Shall
• B. Should
• C. May
• D. Shall not

Answer: (A)

Bonding the lightning protection ground terminals to the building’s grounding electrode system is required to create a single, low-impedance path for lightning energy and to keep all parts of the structure at the same electrical potential during a surge. When the components of a lightning protection system are bonded to the grounding electrode system, there’s no large potential difference between the down conductors, grounding electrodes, and other grounded parts of the structure. This minimizes the risk of arcing, equipment damage, and shock hazards that could occur if the system floated independently.

The word shall conveys that this is a mandatory requirement. Using shall not would imply it's prohibited, which would defeat the protective purpose, while should or may would suggest optionality, reducing the reliability of the protection scheme.