For straight pulls, what is the minimum length of a pull box for cables over 600V?

For straight pulls involving cables rated over 600 volts, the National Electrical Code (NEC) specifies that the minimum length of a pull box must be determined to ensure that the cable can be handled safely and effectively during installation or maintenance. The requirement of having a pull box that is at least eight times the diameter of the largest conductor or cable being pulled helps minimize stress on the conductors and ensures that they can be maneuvered without risk of damage.

This specification is designed to accommodate not just the physical space for the cables but also the necessary clearance and ease of handling during the actual pulling operation. The eight times the diameter guideline is widely recognized in electrical installations and is critical for maintaining the integrity of high-voltage systems. Such standards help prevent issues that could arise from tight bends and angles which might exceed the cable's bending radius, leading to potential failures or hazards.

In contrast, the other proposed length requirements, while relevant for different types of installations or conditions, do not align with the NEC's specific stipulations for straight pulls at voltages exceeding 600V, which is why the eight times the diameter figure is the correct choice.