What is the minimum length for a pull box when using a four-inch RMC for a straight pull with conductors sized 4 AWG or larger?

The minimum length for a pull box in the context of using a four-inch Rigid Metal Conduit (RMC) for a straight pull with conductors sized 4 AWG or larger is established to ensure safe and efficient installation and maintenance of electrical conductors. For conduits with conductors of this size, the National Electrical Code (NEC) specifies that the pull box must be at least 32 inches in length.

This dimension allows sufficient room for the conductors to be pulled through without excessive bending or stressing that could damage the insulation or the conductors themselves. It also facilitates easier access for future maintenance and potential pulling of additional conductors.

Understanding the requirements for pull boxes is essential for ensuring compliance with safety standards in electrical installations, as insufficiently sized pull boxes can lead to issues including overheating, abrasion of conductors, or difficulties in accessing wiring for repairs or changes.