When a substantial structure is metal, what must be done for service conductors passing over a roof?

When service conductors pass over a metal roof, bonding them with a jumper is essential to ensure proper grounding and to maintain electrical safety. The NEC requires that when conductors are in contact with a substantial metal structure, there should be provisions in place to prevent the potential for grounding issues.

Bonding the service conductors ensures that they are electrically connected to the metal structure. This allows for fault current to be safely directed to ground in the event of a fault condition. The installation of a jumper provides a low-resistance path that helps to mitigate electromagnetic interference and reduces the risk of electrical shock or fire hazard resulting from the accumulation of static electricity or other conductive paths.

Isolating the conductors from the structure may lead to potential hazards, as it could result in the loss of an effective ground path. Insulation alone may not provide the necessary grounding features required for safety. Securing with a wire clamp helps to hold the conductors in place but does not address the critical need for bonding in terms of electrical safety. Therefore, bonding with a jumper is the only option that guarantees both secure installation and adherence to safety regulations under the NEC.