supplemental ground

[Big Guns]

Do you size up your supplemental ground conductor to the size of your largest service conductor,

 

[Dennis Alwon]

Do you size up your supplemental ground conductor to the size of your largest service conductor,

What is a supplemental ground conductor? If you mean GEC then yes. Remember that a ground rod only needs a #6 max.

 

[infinity]

You mean a supplemental grounding electrode for the water pipe? Yes, table 250.66. As Dennis stated ground rod only need up to a #6 and a CEE only needs up to a #4.