The scenario: detached garage with a subpanel supplied by a 30a 240v feeder from the house, with two hots, neutral, and EGC. There is also an Ethernet cable from the house to the garage, carrying a phone line, but technically this could be "another metallic path" between the buildings.
The neutrals and EGC are not bonded at the subpanel. EGC at the subpanel is connected to a 1" iron pipe, which goes into the ground and runs horizontally about 30 feet, 18" deep, terminating underground at nothing. (No idea what it was for.)
The questions: do I need a ground rod at the garage, in addition to this pipe? Or is the pipe + EGC from the house sufficient? If I do need a rod, does it need to be 6+ feet away from the pipe?
Best Answer
The NEC requires "grounding electrode(s)", a ground rod is one acceptable electrode. All electrodes that are present are required to be bonded to the service.
To qualify as a service electrode NEC 250.52(A)(5) allows pipe or conduit 8' long, 3/4" min diameter, with a corrosive resistant coating to be used as an electrode. 250.53 requires it be driven to a depth of 8' unless hitting rock bottom, then it can be driven at a 45 degree angle or buried in a trench a minimum 30" deep. Your pipe horizontally buried 18" deep in a trench for convenience it is quite likely to be rejected by the local AHJ. 250.53 also specifies plate, pipe, and rod spacing to be at least 6'.
The connector to the pipe must be NRTL (UL,CSA,MET) Listed for the purpose.
There is also some disagreement about how many electrodes you need, using only a plate, rod, or pipe electrode at a service requires a supplemental electrode. Some jurisdictions allow a single plate, rod, or pipe electrode at an accessory building. I think the argument for the code allowing that is weak, although the logic of a 4th rod electrode could be understandably be argued redundant.