What is the requirement for the bonding jumper that connects to the supplemental grounding electrode when it is a rod?

The requirement for the bonding jumper that connects to a supplemental grounding electrode, such as a ground rod, is that it can indeed be smaller than 6 AWG copper. This allows for flexibility in installations, especially in residential settings, where conductors need to be manageable in size while still maintaining effective grounding. It's important to note that although a bonding jumper can be smaller than 6 AWG copper, it must still meet the overall grounding and bonding requirements outlined in the National Electrical Code (NEC).

The NEC provides guidelines on the minimum sizes for grounding conductors, and while larger conductors may provide additional protection against potential fault currents, they are not always necessary for supplemental electrodes. Therefore, using a smaller size that still complies with the NEC's provisions allows for safe and effective grounding in various residential applications.

In contrast, other options suggest requirements for larger conductors, which are not aligned with the NEC for these specific circumstances.