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Thread: Branch circuit, short circuit and ground fault protection for ac motor

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    Branch circuit, short circuit and ground fault protection for ac motor

    I have a test question that reads no exceptions apply maximum standard size non delay fuse permitted for branch circuit short circuit and ground fault protection for AC motor where given the following: 2 hp- 120 volt single phase, continuous duty, nameplate current rating 22 amps.

    Calculations give 72 amp
    I chose 80 amps for the protection
    The answer sheet said you must go down to 70 in this case
    I could not find a reason why to go down in amperage
    What is correct?

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    Quote Originally Posted by Chuck 1961 View Post
    I have a test question that reads no exceptions apply maximum standard size non delay fuse permitted for branch circuit short circuit and ground fault protection for AC motor where given the following: 2 hp- 120 volt single phase, continuous duty, nameplate current rating 22 amps.
    An 80A fuse would be allowed under exception no 1 to Table 430.52.

    If "no exceptions apply" then I would say the max size would be 70A.

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    The right overcurrent protection

    They did use 24 amp as stated in the table
    But I understand now after going back and reviewing 430.52(C)1
    With no exceptions!

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    The right overcurrent protection

    Thank you for your help you’ve been quite helpful!

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