What is the smallest system bonding jumper you can install in the 300 A panel board?

The smallest system bonding jumper that can be installed in a 300 A panel board is determined by the National Electrical Code (NEC) requirements. According to NEC Table 250.102, bonding jumpers must have a specific size based on the ampacity of the service entrance conductors.

For a 300 A panel board, the relevant bonding jumper is typically sized according to the size of the service conductors. In cases where the normal size falls below certain thresholds, such as a bonding jumper that must be at least equal to a specific minimum size pertaining to the system's requirements, a size of 2 AWG copper is often the minimum for systems involving specific bonding needs. This makes it suitable for ensuring adequate grounding and bonding, thus promoting safety and reliability.

As a result, opting for the number 2 AWG jumper aligns with both code requirements and practical considerations for grounding systems, making it suitable for installation in a 300 A panel board.