AVS Special Member
Join Date: Nov 2001
Location: College Park, MD
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To be functionally "as good as code" without meeting the letter of the code, you do need to drive the 8 foot grounding rod, and from there, you could bond the rod to the system in a non-compliant manner at the sub panel, but if I were doing that, like if I had a busybody customer who was watching me install and kept insisting I had to ground according to code, I'd connect to the subpanel but I wouldn't penetrate the box with my ground wire. I'd either ground to the box itself or clamp it to the raceway, which is the name commonly used to describe the conduit that sources the subpanel, using a clamp like the one shown above.
If you ground it to the box, you are NOT allowed to use a cover screw for attachment of any ground wire, as any attachment terminal must be for that ground wire only. There are doo-dads that can be screwed to the box that cost less than two dollars. One kind is a corner clamp that does not require driling a pilot hole in the box, the other is a tab that you attach to the side of it using a sheet metal screw.
My preference would be to use one of those water pipe clamps to attach to the raceway.
Back when the code was originally written, home electric services has a small box with two big cartridge fuses in it. I think I've seen 50 and 70 amp cartridge fuses, but bigger houses than the ones I've lived in could well have had larger ones. And that box was the service entrance and while it was technically permissible to backbond to that box because it was considered to be a part of the ground electrode system whereas the main fuse box, with its screw-in glass fuses, was not. Then the breaker box that combined the functions of those two boxes became the product that all new homes used, but the code didn't immediately come up with a name for that which distinguished it from a box that just provided the initial, full circuit protection only, and it didn't explicitly say whether a back bond to the ground electrode system could be made to that multifunction box or panel. One would need a shelf full of successive editions of the NEC, issued every three years, to see how their terminology lags the products we deal with in the field.