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Electrical Single Line Question

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    Electrical Single Line Question

    Hello All,

    When looking at a single line drawing, if circuit breaker ratings don't specify AT or AF but only have one rating, such as 400A, does that indicate the breaker is a 400AF or set to 400AT?

    I hope my question makes sense.

    Thanks!

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    Quote Originally Posted by Joshua122042 View Post
    Hello All,

    When looking at a single line drawing, if circuit breaker ratings don't specify AT or AF but only have one rating, such as 400A, does that indicate the breaker is a 400AF or set to 400AT?

    I hope my question makes sense.

    Thanks!
    It is likely a designation for a fixed size breaker, where there is no ability to vary the breaker rating via a rating plug or settings. It could also be preliminary design drawings were the type/manufacturer of the breakers is not known, so it is simply specifying the required rating, which in this example could end up being something like 800AF/400AT or several other legitimate combinations.

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    Quote Originally Posted by Wanderer20001us View Post
    It is likely a designation for a fixed size breaker, where there is no ability to vary the breaker rating via a rating plug or settings. It could also be preliminary design drawings were the type/manufacturer of the breakers is not known, so it is simply specifying the required rating, which in this example could end up being something like 800AF/400AT or several other legitimate combinations.
    Thanks for the info! This answer my questions perfectly.

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    Quote Originally Posted by Joshua122042 View Post
    Hello All,

    When looking at a single line drawing, if circuit breaker ratings don't specify AT or AF but only have one rating, such as 400A, does that indicate the breaker is a 400AF or set to 400AT?

    I hope my question makes sense.

    Thanks!
    Most likely the frame provision for that section. Switchgear cells are typically sized for a specific frame size and the sensors/plug are used to determine the continuous current rating for the particular load.

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