Ground conductor for existing detached garage

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ckelley3

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I am currently running a feeder to an existing detached garage and have a question on the ground conductor run with the ungrounded conductors as part of the feeder. I had planned to use 6/3 romex from the main service panel, through the house basement to a junction box near the outside wall (but still inside the structure, then RMC from the junction box, through the basement wall, (underground) and up to a new sub-panel in the detached garage. I am installing a ground rod just outside the detached garage and bonding it to the subpanel ground bus with #6 copper. I just now ran across 250.32 (e) and it appears the #8 ground wire in the romex is too small and needs to be a #6 (meaning I should have used SER instead of Romex) for the portion of the feeder that is inside the main structure. Can anyone confirm this?
 
I think we might be mixing apples and oranges. The equipment ground routed with your feeder would be sized per 250.122 and the OCP. With a 6/3 NM it is probably a #10 which matches the 60? rating of #6 NM (55 amps)
It terminates (normally on a grounding bar) where your structure EGC and GEC will also land. 250.32(E), IMO, is only discussing the GEC from that termination to the grounding electrode.
 
One other potential issue came to mind......because I am using romex for part of the feeder wiring, does this mean I am limited to the 60 degree ampacity rating for the feeder and just shy of the 60A minimum disconnect size for a feeder with 3 or more circuits? If so, looks like I am stuck using a 50A breaker in the service panel and a 60 amp disconnect in the garage panel.
 
Just came across 240.4 (B), which says it is permissible to use the next size breaker up, since the 55A is not available. Looks like the 60A will be OK on both ends.
 
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