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Thread: Transformer "Secondary" OCPD

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    Transformer "Secondary" OCPD

    This seems like a simple/stupid question that I can't find the answer to. Maybe you all can help.

    When secondary overcurrent protection devices are mentioned in Table 450.3(B), what counts as secondary OCPD? Does this have to be a stand-alone device (some separately mounted panel with a fuse or circuit breaker) or would an MCB for a downstream panel (switchboard, panelboard, etc) be adequate?

    Can you all point me to a definition or a qualifier somewhere within the NEC?

    Thanks for all your help,
    --Nate K.
    (Baltimore, MD)

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    Quote Originally Posted by BlaineXD View Post
    This seems like a simple/stupid question that I can't find the answer to. Maybe you all can help.

    When secondary overcurrent protection devices are mentioned in Table 450.3(B), what counts as secondary OCPD? Does this have to be a stand-alone device (some separately mounted panel with a fuse or circuit breaker) or would an MCB for a downstream panel (switchboard, panelboard, etc) be adequate?

    Can you all point me to a definition or a qualifier somewhere within the NEC?

    Thanks for all your help,
    --Nate K.
    (Baltimore, MD)
    it can be separate or part of a panel board.
    Bob

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    Quote Originally Posted by petersonra View Post
    it can be separate or part of a panel board.
    Certainly true but I think the OP needs to know that there is more to this than Article 450. OP, see 240.21(C) for transformer secondary conductors.

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    Quote Originally Posted by texie View Post
    Certainly true but I think the OP needs to know that there is more to this than Article 450. OP, see 240.21(C) for transformer secondary conductors.
    It is true that both the transformer secondary and the transformer secondary conductors have to have protection. it can be the same device.
    Bob

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    Quote Originally Posted by petersonra View Post
    It is true that both the transformer secondary and the transformer secondary conductors have to have protection. it can be the same device.
    I'm not disagreeing with you, just adding a little info to help the OP.

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    Quote Originally Posted by texie View Post
    I'm not disagreeing with you, just adding a little info to help the OP.
    The OP appreciates the extra info!

    Thanks for the clarification, all.

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    One more thing worth noting is the panel board needs protection too (408.36). Often you will have one ocpd meeting all three requirements.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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