In the application of flexible metal conduit for an air-handling unit, what must be included to ensure safety?

In the application of flexible metal conduit for an air-handling unit, the inclusion of an Equipment Grounding Conductor (EGC) is essential for safety. This requirement is in place to ensure that any fault currents are safely carried away to ground, protecting both the equipment and personnel from the dangers of electric shock or fire. Flexible metal conduit can provide some degree of grounding capability; however, it is not sufficient on its own, especially where equipment may be subject to movement or vibration, which could compromise the integrity of the ground connection.

By requiring an EGC regardless of the conduit length, regulatory standards ensure that there is always a reliable path for electrical fault currents. This conductance is critical in installations where equipment may experience faults, as it prevents voltages from rising to a level that could pose danger.

The other choices, while relevant to electrical installations, do not directly address the grounding and safety concerns associated with the flexible metal conduit in the specific context of air-handling units. Ensuring that an EGC is in place covers the fundamental aspect of electrical safety in such installations.