What is the minimum length for a pull box when a run of three-inch RMC is installed for a straight pull?

In the context of electrical installations, particularly when dealing with rigid metal conduit (RMC) and pull boxes, the minimum lengths are determined by the National Electrical Code (NEC) recommendations to ensure safe and effective handling of cable pulls.

For a straight pull, the NEC requires that the pull box should be long enough to facilitate the pulling of wires without causing strain or damage. Specifically, the minimum length for a pull box for a three-inch RMC during a straight pull is 18 inches. This dimension is derived from NEC guidelines that seek to ensure proper installation practices, allowing enough space for the conductors to be pulled in smoothly. The primary goal is to reduce the risk of damaging the conductors by providing adequate room during installation.

Understanding these guidelines helps ensure compliance with code requirements and promotes safety in electrical installations, making it crucial for professionals in the field to be familiar with these measurements.