For large service-entrance conductors over the specified sizes, what percentage of the conductor area must the main bonding jumper be?

The main bonding jumper plays a critical role in ensuring a low-resistance path for fault currents and helps to keep the electrical system safe and compliant with the regulations set forth in the National Electrical Code (NEC). The requirement that the main bonding jumper must be a specific percentage of the conductor area ensures that it is adequately sized to handle any fault current that could occur.

For large service-entrance conductors, the NEC specifies that the main bonding jumper must be 12.5% of the area of the conductors. This percentage is determined based on the need to effectively bond the neutral and ground together while still allowing sufficient current-carrying capacity to safely manage the electrical loads and potential fault conditions.

In scenarios where conductors are larger and capable of carrying more current, it becomes even more crucial to have a bonding jumper that reflects this larger capacity, reinforcing equipment and personnel safety. By having this specified percentage, the NEC aims to standardize practices and promote safe electrical installations.

Other percentage options do not meet the same standards as established by the NEC for large conductors and could lead to inadequate bonding which can compromise system safety. The 12.5% requirement serves as a benchmark within the industry, ensuring that installations are consistent and secure across different