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Thread: Formulas in the NEC Code Book

  1. #1
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    Formulas in the NEC Code Book

    I'm in fourth year electrical school and I have a question: Does anyone know why the formulas for voltage drop, motors, The Wire Wheel, and transformer calculations are not in the NEC Code Book? Does anyone else feel it's a good idea to have these somewhere in the code book? The only answer I've ever recieved, is we should know them by heart before we take the Journeymans Exam. I'm just wondering, since these are so important, why are they not present in the code book.

    Thanks in advance for all responses!

  2. #2
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    Got a pen? Write um in. Its a code book not a math book.

  3. #3
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    Does anyone else feel it's a good idea to have these somewhere in the code book?
    The information you are asking for is used in designing the system. The code book is not a design manual.

  4. #4
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    Re: Formulas in the NEC Code Book

    Quote Originally Posted by vermathrax
    Does anyone know why the formulas for voltage drop, motors, The Wire Wheel, and transformer calculations are not in the NEC Code Book?
    Yes........well, I think I know.

    90.1 Purpose.

    (C) Intention.
    This Code is not intended as a design specification or an instruction manual for untrained persons.
    That aside I recommend doing what bikeindy suggested, write the things you want into the blank pages.

  5. #5
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    Re: Formulas in the NEC Code Book

    Quote Originally Posted by iwire
    That aside I recommend doing what bikeindy suggested, write the things you want into the blank pages.
    I agree. Only one note of caution: Most testing agencies won't let you have handwritten notes in your book during a test. You might consider putting them in there with sticky notes so you can peel them out prior to the test.
    Brad Darnell
    Master Electrician -Electrical Contractor
    IN-NJ-WI-CT-LA-OH-KY-TX-FL-NV-GA-TN-MS-OK-IL-NC-AL-KS

    "The Code doesn't say what you think it says" - Charles E. Beck, P.E.

  6. #6
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    One of my favorite sayings is from Einstein. Someone asked him a question and his answer was, I will have to look it up. His famous quote is:
    " I never memorize what I can look up"

    I agree with that, hence I do not agree we need to memorize any of those formulas when we can write them down somewhere to look up.
    Write them in your book somewhere, so when you will need them, you will be able to look them up.


    In reality how often does the average electrician use formulas for calculations on the job? Not too often... but if they were written down somewhere, they may use them more often.
    Instructor, Industry Advocate

  7. #7
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    Quote Originally Posted by Pierre C Belarge
    In reality how often does the average electrician use formulas for calculations on the job?
    Everyday. Wire sizing, motor overload sizing, pipe fill, box fill, wireway fill, branch circuit, feeder, service calculations and most importantly paycheck calculations, to name just a few.

  8. #8
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    I think it would be a good idea to have another appendix with some of the formulas listed. It would make the Code book more useful and would actually be a selling point.
    In fact, the real question should be: what formulas should be included?
    For one, Ohm's law show be included. It is obviously enforceable.
    Also that complicated formula for the current on the neutral of a three phase system. How can you memorize the square root of A times B plus B times C minus whatever?? [See I haven't yet memorized it ]
    Also the formulas for resistance and capacitance in parallel and series circuits. These do show up on tests and it would be a plus point to have this available in black and white during a test and even at home or at work.
    These formulas are not an instruction manual but rather bits of easily forgotten/confused but vital aspects of the practice of electricians. And, I repeat, these are enforcible. After all, the Code is a law book [with all it obfuscation and legalese, and the inspector can easily issue you a red for violating Kirscoff's law.
    ~Peter

  9. #9
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    Quote Originally Posted by colosparker
    Quote Originally Posted by Pierre C Belarge
    In reality how often does the average electrician use formulas for calculations on the job?
    Everyday. Wire sizing, motor overload sizing, pipe fill, box fill, wireway fill, branch circuit, feeder, service calculations
    In reality it is the minority of electricians that need to do any of that on a regular basis.

  10. #10
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    Quote Originally Posted by peter
    For one, Ohm's law show be included. It is obviously enforceable.
    Can you explain?


    Quote Originally Posted by peter
    These formulas are not an instruction manual but rather bits of easily forgotten/confused but vital aspects of the practice of electricians. And, I repeat, these are enforcible. After all, the Code is a law book [with all it obfuscation and legalese, and the inspector can easily issue you a red for violating Kirscoff's law.
    Peter what section is cited for violating Kirchoff's law?

    Is it even possible to violate Kirchoff's law?

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