When IMC enters a box, fitting, or enclosure, what is required to protect the wire from abrasion?

• A. a bushing
• B. a cable gland
• C. a conduit seal
• D. a thread protector

Answer: (A)

When metal conduit like IMC enters a box or enclosure, the sharp edge of the knockout can nick or abrade the conductor insulation as the wires pass through. A bushing is used at the entry to provide a smooth, rounded surface and to support the conductors, preventing abrasion and reducing the chance of insulation damage or future faults. The other items don’t fit this protection role: a cable gland is for sealing and strain relief at certain cable types, not specifically to shield wires from edge abrasion; a conduit seal is meant to seal against moisture or air and doesn’t protect the conductor insulation; a thread protector guards the conduit threads rather than safeguarding the wire inside. So the bushing is the proper protective device for this situation.