I am helping family with finishing and upgrading the service to a separate garage 30ft from the house. Currently, there is 12-2 NM w/ground on a 20 amp breaker cord-capped and plugged in to a receptacle under the deck. The pvc is just stubbed up and unfinished under the deck and outside the garage. I'm going to j-box it up and pipe it all in. I intend to pull #6 THHN and install a two pole 60 amp breaker. My question is can I use the EGC there at the 200 amp panel in the basement or do I need to get my own out there at the garage? Is this treated as a separately derived system?
Equipment ground
grounding
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Best Answer
Pull an EGC and put a ground electrode in
You'll need to pull an equipment grounding conductor (although it doesn't have to be a 6AWG -- a 10AWG bare copper wire will do as per Table 250.122, and also saves on conduit fill) with the garage feeder from the main panel, and put a grounding electrode such as a ground rod in at the garage since it's a separate structure.
The EGC will provide a conductive bonding path to the main panel for fault currents, while the grounding electrode makes sure that the garage wiring doesn't get elevated to a high common-mode voltage relative to the earth itself (say by a nearby lightning strike). Tie the garage grounding electrode to the EGC at the garage disconnect/subpanel (which will need its bonding strap/screw pulled) with more 10AWG copper wire (250.32(B) says this connection is an extension of the EGC).