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Does a subpanel need a grounding rod when the subpanel is within the same structure as the main panel?

Does a subpanel need a grounding rod when it is in an outbuilding?

Are there any distance considerations?

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    No, but it needs to be connected to the building's grounding system and associated rods or other electrodes. Yes, No. And neutral and ground are always separate in a sub-panel, regardless of whether it needs a rod. And usually if it needs a rod, it needs TWO.
    – Ecnerwal
    Oct 7, 2021 at 18:17
  • @Ecnerwal, when does it need two? Just based upon the 25 ohm rule?
    – mongo
    Oct 8, 2021 at 19:26

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No. Post-2008, system safety ground (Equipment Grounding Conductor) must be carried to all panels in the entire distribution, whether in the same building or a different building.

And also, each building needs a set of ground rods. But only 1 per building.

Officially "a breezeway" will turn 2 buildings into 1 building for NEC reasons. However, your AHJ may view that differently if you have a vast interconnected complex.

Generally speaking, too many ground rods "can't hurt, might help".

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