What is the size of the largest conductor permitted when connecting to a ground rod?

The largest conductor size permitted when connecting to a ground rod is #6 AWG. This is in accordance with the National Electrical Code (NEC), which establishes guidelines for grounding and bonding conductors. The reason why #6 is acceptable and often specified is due to its ability to handle the maximum fault current that could occur without risking a loss of its grounding effectiveness.

Grounding provides a path for fault currents to safely dissipate into the earth, thus protecting the electrical system and ensuring safety. The #6 AWG wire is solid enough to provide good conductivity and withstand potential corrosion over time, which is important because ground rods are typically installed underground, where they are subject to moisture and soil conditions that can degrade lesser materials over time.

The other sizes, such as #4, #8, and #10 AWG, are either too large or too small according to the NEC guidelines for grounding conductors connected to ground rods, making #6 the best choice for both compliance and safety standards.