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Thread: motor circuit condutor derating

  1. #1
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    motor circuit condutor derating

    If you have a raceway that has motor control circuit conductor and more than 3 motor circuit conductors in the raceway, are you required to derate the motor circuit conductors?
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  2. #2
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    Quote Originally Posted by don_resqcapt19 View Post
    If you have a raceway that has motor control circuit conductor and more than 3 motor circuit conductors in the raceway, are you required to derate the motor circuit conductors?
    TTBOMK, yes.
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  3. #3
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    I believe I agree with Smart. Not sure if it applies, but If surface metal raceway, then see 386.22.
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    Quote Originally Posted by resistance View Post
    I believe I agree with Smart. Not sure if it applies, but If surface metal raceway, then see 386.22.
    Since the OP mentions the more generic term raceway, that's a very good point. Also needing noted are wireway and cable tray installations having different derating requirements.
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  5. #5
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    I was not really thinking about raceways other than conduit.
    Don, Illinois
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  6. #6
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    Quote Originally Posted by don_resqcapt19 View Post
    I was not really thinking about raceways other than conduit.
    Neither was I in my first reply
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  7. #7
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    I have always thought that the control conductors do not have to be counted as current carrying conductors when derating conductor ampacities. It has been a long time since I had made that conclusion and am not sure if there have been changes in code since then. What I am finding now seems to be clear that the control conductors do not need derated, but is not clear whether or not the other conductors need to include the controls when determining how many current carrying conductors are in the raceway.

    725.43 Class 1 Circuit Overcurrent Protection. Overcurrent protection for conductors 14 AWG and larger shall be provided in accordance with the conductor ampacity, without applying the ampacity adjustment and correction factors of 310.15 to the ampacity calculation. Overcurrent protection shall not exceed 7 amperes for 18 AWG conductors and 10 amperes for 16 AWG.
    I haven't looked but I think a few code cycles back some of this information was in 430 and has moved to 725, don't know if it just moved or if there were changes to the content also.

  8. #8
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    Quote Originally Posted by kwired View Post
    I have always thought that the control conductors do not have to be counted as current carrying conductors when derating conductor ampacities...
    It is still just power and lighting conductors get derated.

    OP stated, "more than 3 motor circuit conductors in the raceway".
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  9. #9
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    Quote Originally Posted by Smart $ View Post
    It is still just power and lighting conductors get derated.

    OP stated, "more than 3 motor circuit conductors in the raceway".
    Well yes you do derate the motor conductors if more than three no matter what else is in the raceway, except cold temperature in the raceway allows for uprating on top of the derating.

  10. #10
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    Quote Originally Posted by kwired View Post
    Well yes you do derate the motor conductors if more than three no matter what else is in the raceway, ...
    Code section?
    Don, Illinois
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