In what scenario is a separate bonding jumper required when using flexible metal conduit?

A separate bonding jumper is required when using flexible metal conduit specifically when the conduit length exceeds 6 feet. This requirement is in place to ensure proper grounding and bonding for safety reasons. Flexible metal conduit is not inherently a conductive grounding path, especially over longer distances, and it is essential for the electrical system to maintain an effective ground fault current path. By bonding the conduit, you establish electrical continuity and ensure that any fault current is directed safely back to the ground, reducing the risk of electrical shock or fire.

This bonding jumper acts as a supplemental path that helps ensure that the conduit itself can safely carry fault currents. This is especially critical in applications where the flexibility of the conduit can compromise the continuity of the grounding path.

Other scenarios such as the conduit being indoors, exceeding 10 feet, or having multiple circuits do not specifically necessitate a separate bonding jumper under the same definitive conditions as outlined by electrical codes, making the requirement based solely on conduit length exceeding 6 feet the key factor in this context.