Q. When are insulated bushings required on raceway terminations?

A. Where raceways contain conductors 4 AWG and larger, the conductors must be protected from abrasion during and after installation by a fitting that provides a smooth, rounded insulating surface, such as an insulating bushing [300.4(F)]. For IMC and RMC, a metal or plastic bushing must be installed on conduit threads at terminations, regardless of conductor size, in accordance with 300.4(F), unless the design of the box, fitting, or enclosure is such as to afford equivalent protection [342.46 and 344.46].