You would be paralleling grounds and it could cause objectionable current. I have seen instances where a G.E.C. was installed and not needed and by disconnecting it, solved some issues.
Just where would the objectionable current come from? If the ground rod is tied only to the EGC there is no current on that wire short of a fault.
A ground rod, or other GES is required at a separate structure. Where the GEC lands in the subpanel depends on whether an EGC was ran with the feeder or not. If there was an EGC, then the GEC would land on the EGC bar, if not, it would land on the neutral bar. In either case it shouldn't affect a GFCI.
Would you please show me a code reference that requires a grounding electrode at a separate structure? Art. 250.32 (ex.) excludes the G.E.S. if supplied by a single branch circuit.
That's true. But has nothing to do with the question at hand.
I believe we were talking about a subpanel
