What is the minimum length of a box for straight pulls of conductors 4 AWG and larger relative to the trade diameter of the largest raceway?

The minimum length of a box for straight pulls of conductors that are 4 AWG and larger is determined by the trade diameter of the largest raceway. According to the National Electrical Code (NEC), for straight pulls, the box must be at least eight times the trade diameter of the largest raceway involved in the pull. This requirement exists to ensure that there is adequate space within the box to allow for the bending and pulling of conductors without causing damage, maintaining the integrity and safety of the electrical installation.

This specification helps prevent issues such as conductor stress, which can arise if the conductors are forced into a confined space, leading to potential insulation damage or connectivity issues. Having a box that meets this minimum length also facilitates easier handling of the conductors during installation or maintenance.

Understanding this guideline is crucial for compliance with NEC regulations and for ensuring safe and effective electrical installations. The other options related to lengths shorter than eight times the trade diameter would not provide a sufficient margin for the safe handling of the conductors during pulls.