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Thread: 320/400 Dual Panel Service Bonded at the Panels - GEC Current

  1. #31
    Join Date
    Aug 2018
    One other point of clarification. The parallel paths at the "Service" do not adversely affect the main safety mechanisms on the load side of the Service. Ground faults are still brought back to the Service via the EGC, and connected to the neutral establishing path-to-source and ultimate OCPD protection. The parallel path mantra at sub panels (or anywhere else downstream of the Service) is still valid. Those parallel paths energize the EGC and subsequently all the objects along the way, subjecting occupants to potential touch danger. So the "no parallel paths" thinking is still a good way to think. That said, this problem does not exist at the Service in the same way it exists down the line. GFCI's still work fine as the direction the neutral current bends at the panel doesn't matter. Even GFCI breakers are fine because that current is measured before the circuit neutral returns to the bar.

    My original concern, perhaps alleviated mostly herein, was putting too much current on the taps. I don't have any concerns downstream.

  2. #32
    Join Date
    May 2005
    Richmond, Virginia
    Quote Originally Posted by JPinVA View Post
    Could not the same thing be stated today, but wrt to the GEC tap? If one panel neutral fails, the tap becomes the neutral path, with current riding the GEC to the other panel neutrals and back to source. I guess one could argue having these two paths might help avoid the consequences of a failed panel neutral...provided there was enough other issues with the failure to get one's attention.
    I was actually referring to services in separate houses. For example, a bad neutral in your house sending its imbalance current through the GEC to the water service piping to the neighbors' houses, using their GEC's as a pathway to their neutrals. That's one reason water meters are supposed to have jumpers around them.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  3. #33
    Join Date
    Dec 2007
    NE Nebraska
    Quote Originally Posted by JPinVA View Post
    The issue I'm concerned about isn't the parallel paths with a panel's neutral to the trough. The issue I'm concerned about is a parallel path that runs from the neutral in Panel 1 through the neutral in Panel 2 and vice versa.
    I'd be more concerned about other pathways one doesn't immediately concern themselves with instead of this relatively short path between the two adjacent panels.

    Any and all bonded objects on the premises are a potential path for neutral current if the right sequence of failures occurs. In fact many of said objects already will be carrying some of the neutral current but as long as connections back at the main leads of the panels are in good condition they should still carry a very large majority of the current because that should be the lowest resistance path. A rather small amount of current is also flowing in the grounding electrode - but again it should be high enough resistance to remain a very small amount as long as the main conductors remain in good condition.
    I live for today, I'm just a day behind.

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