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Thread: Is it a main panel or a subpanel

  1. #1
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    Is it a main panel or a subpanel

    Older commercial building with 400 amp single phase service. The power company lines come into the building and go directly to a fused 400 amp disconnect. From there they split to a 200 amp fused disconnect and two 100 amp disconnects.
    At the end of each of those 3 disconnects are modern day 200 amp panel and two 100 amp panels. Are those modern day panels main panels or subpanels? Do I isolate the ground and neutral bars or leave them connected on these modern day panels?

  2. #2
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    Technically, since they are all after the service point, the first fused disconnect is the main and is where the bond should be located.
    Everything downstream is a sub panel and should be wired with separate neutral and EGC, without bonds.

    At a minimum, even considering the two second level disconnects as grandfathered, the new panels should all be fed by separate neutral and EGC.
    If they are not separately fed, then you cannot avoid bonding the neutral and EGC buses in them, but you should still not mix the two types of wires within the panel in case you end up needing to separate them later.

  3. #3
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    Quote Originally Posted by hardworker View Post
    Older commercial building with 400 amp single phase service. The power company lines come into the building and go directly to a fused 400 amp disconnect. From there they split to a 200 amp fused disconnect and two 100 amp disconnects.
    At the end of each of those 3 disconnects are modern day 200 amp panel and two 100 amp panels. Are those modern day panels main panels or subpanels? Do I isolate the ground and neutral bars or leave them connected on these modern day panels?
    Modern day panel or not, they are not the first means of disconnect with overcurrent protection. Any panel (fused or breaker) past the first one is a subpanel. Yes grounds and neutrals are to be separated.
    If you aim at nothing, you will hit it every time!

  4. #4
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    Quote Originally Posted by Little Bill View Post
    Modern day panel or not, they are not the first means of disconnect with overcurrent protection. Any panel (fused or breaker) past the first one is a subpanel. Yes grounds and neutrals are to be separated.
    I was taught that fused disconnects on these old systems are not considered a main panel. The first panel that distributes is considered the main panel and everything downstream is a sub. Please comment on this subject, because I get different answers from different electricians.

  5. #5
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    Quote Originally Posted by hardworker View Post
    Older commercial building with 400 amp single phase service. The power company lines come into the building and go directly to a fused 400 amp disconnect. From there they split to a 200 amp fused disconnect and two 100 amp disconnects.
    At the end of each of those 3 disconnects are modern day 200 amp panel and two 100 amp panels. Are those modern day panels main panels or subpanels? Do I isolate the ground and neutral bars or leave them connected on these modern day panels?

    Where is the metering equipment in this setup?
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  6. #6
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    Quote Originally Posted by infinity View Post
    Where is the metering equipment in this setup?
    Meter is installed downstream from main disconnect, believe it or not. All this equipment is located inside the building.

  7. #7
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    Quote Originally Posted by hardworker View Post
    Meter is installed downstream from main disconnect, believe it or not. All this equipment is located inside the building.
    If POCO considers the service point to be downstream of the first fused disconnect, then the next OCPD after the service point would be the main.
    But POCO would probably want to seal the upstream disconnect.

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