Mike Dolt Enterprises
Mike Dolt Enterprises
User: ckelley3, Location: Tennessee
Asked on: Friday, April 29, 2011 at 10:16 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:49 am EDT
Question: 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?
Yes, you are correct. According to NEC 250.32(E), the grounding conductor for a feeder must be at least the same size as the largest ungrounded conductor in the feeder. For a 6/3 NM cable, the largest ungrounded conductor is #6, so you would need to use a #6 grounding conductor. Since NM cable only comes with an #8 grounding conductor, you cannot use NM cable for this application. You would need to use a cable type that is available with a #6 grounding conductor, such as SER cable. Flag for review