What is the maximum size for a grounding electrode required if the connection to earth is through a single ground rod?

The maximum size for a grounding electrode connection to earth when utilizing a single ground rod is indeed specified in the National Electrical Code (NEC). For a ground rod installation, the NEC allows copper conductors up to a maximum of 6 AWG when connecting to ground rods, regardless of the size of the ground rod itself.

Using a 6 AWG copper conductor ensures effective grounding while still adhering to minimum safety standards set forth by the NEC. Grounding electrodes, such as ground rods, are crucial for electrical safety, as they provide a direct path for electric faults to dissipate safely into the earth.

In this context, larger sizes such as 2 AWG or 3/0 AWG copper would exceed the requirements for a single ground rod connection, which relevant regulations do not necessitate. Therefore, the choice of 6 AWG copper aligns perfectly with the guidelines established for grounding electrode conductors connected to a single ground rod.