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Thread: Generator breaker sizing

  1. #1
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    Generator breaker sizing

    I have emergency generator 200kva, 480V, 3 phase. What would be appropriate overcurrent size for the emergency generator per Nec 2014?

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  2. #2
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    I have emergency generator 200kva, 480V, 3 phase. What would be appropriate overcurrent breaker size (OCPD) for the emergency generator per Nec 2014?



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  3. #3
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    Manufacturer

    The generator manufacturer will have a standard OCPD for the generator.
    e^(i pi) = -1

  4. #4
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    276 amps, so a 300-amp breaker with 300-amp cable.

  5. #5
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    Quote Originally Posted by beanland View Post
    The generator manufacturer will have a standard OCPD for the generator.
    Yea but in my case I have to update the emergency generator load and so I was wondering what the new circuit breaker size be. I have 225 amps ATS downstream.

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  6. #6
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    Quote Originally Posted by codequestion View Post
    Yea but in my case I have to update the emergency generator load and so I was wondering what the new circuit breaker size be. I have 225 amps ATS downstream.

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    Then there's your answer, 225 amps. Just make sure there's less than 225 amps of load at any given time.

  7. #7
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    Quote Originally Posted by mayanees View Post
    Then there's your answer, 225 amps. Just make sure there's less than 225 amps of load at any given time.
    Their was change order. Ats is now 250 amps. So FLA is less than 250 amps. How does this work in terms of sizing breaker?

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  8. #8
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    Quote Originally Posted by codequestion View Post
    Their was change order. Ats is now 250 amps. So FLA is less than 250 amps. How does this work in terms of sizing breaker?

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    When you get all the changes in order come back and start a new thread with all the correct information.

    Roger
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