What is the requirement for insulating bushings when using conduit?

The requirement for insulating bushings when using conduit is essential for preventing conductor damage. Insulating bushings are designed to protect conductors from potential sharp edges and rough surfaces that could lead to insulation wear or a breakdown in the conductor itself. When conductors are pulled through conduit, especially in metal conduits, sharp edges can lead to physical damage, which might result in short circuits or failures.

Using insulating bushings ensures that the conductors have a safe passage through the conduit without the risk of abrasion or cutting. This protective measure helps maintain the integrity of the electrical system, ensuring safe and reliable operation. Hence, requiring them in installations is a key safety practice outlined in the NEC.