As the subject suggests, I'd like to know what size grounding electrode conductor I need for a 125 amp sub panel in my detached garage? This conductor will be attached to 2x 8' grounding rods.
The main panel in the house is 200amps (and of course has it's own GEC & grounding rods).
Oh! and should it be solid or stranded (or does it matter)?
Thanks!!!
250.66 for GEC sizing goes by the size of the largest ungrounded conductor, not by the size of the service or the over-current device like 250.66.
However, even if you are allowed to go with a #6 or #8, either of those will require physical protection which is why most electricians just go to a #4 solid.
BTW the connection to grounding rods is never
required to be larger than a #6 regardless of service or service conductor size, this rule does not apply to the main GEC.
I've never seen #4 stranded GEC used on a service but I suppose you could, I've only seen stranded grounding/bonding conductors used on pool equipment.
If you choose to go smaller than #4 either protect it above ground with schedule 80 electrical PVC, or if metallic conduit is used you must bond the pipe at both ends.
