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I have a main 200 amp feeder panel which is bonded. It feeds a separate 200 amp distribution panel with about 30 circuit breakers which is also bonded. That situation existed since house was built 12 years ago.

I do intend to remove that neutral to ground bar in that distribution panel. I should do that, right?

My question may be moot after that is done but I'm still wondering that if a short to ground on one of those circuits would put voltage on the ground conductors and cases which are grounded. That voltage would disappear once the breaker tripped, right?

Now what if that short circuit resistance was not enough to trip the breaker? Then there would be some voltage on the ground conductors and cases that are grounded. Seems like that should have happened by now. Have we been exceptionally lucky?

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  • One reason GFCIs are required so much now, they trip at very low amounts of wrong placed current.
    – crip659
    Sep 27, 2022 at 15:24
  • Slow down, there are Code requirements for how to do this. Is there a separate neutral wire and ground WIRE between the main panel and the subpanel? Dirt does not count as a wire. Sep 27, 2022 at 19:27
  • Yep. sure is a ground wire and neutral wire separate. Big fat ones, same size as the two Hots. "Dirt does not count as a conductor", I like that.
    – ctaylor
    Sep 29, 2022 at 20:49

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"Shorts to ground" can vary immensely: It could be a direct short where a hot was contacting a ground, or it could be leakage current from a somewhat defective appliance, or even just moisture in a fixture box. Many leaks to ground aren't nearly enough to trip a normal breaker, that's why we have GFCI breakers now which will trip with the slightest leak to ground.

You didn't say whether you had an actual ground fault, so is this an academic question? Putting an amp clamp meter on your ground connections could tell you if you have actual current flowing on your ground.

Your plan to separate the grounds from the neutrals and float the neutral is correct for a sub-panel. You'll need a 4 wire supply to the sub (2 hots, neutral, and a ground). As long as the sub is in the same building, you don't need additional ground rods, but if it's in a separate structure, you will need 2 more ground rods installed and connected to the sub's grounding bus bar.

Have you been "lucky"? Not really, that's what grounding, GFCIs and AFCIs are for. Still, it could be better and you're working on that.

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