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Single phase AC 3 wire neutral conductor shock potential?

  1. Jun 13, 2018 #1
    I have a question with regard to split single phase (in United States) electricity. I understand that there are 2 hot legs each 180 degrees out of phase at +120v and -120v (240v between hot legs) going from transformer to breaker box and a center tapped neutral earth bonded wire at 0v with respect to ground. So if a light bulb is my load on 120v circuit (hot leg and neutral), aren't both the "hot" and "neutral" carrying carrying the whole time in opposite directions? The bulb doesnt care which is which because the polarity changes 60 times per second right?
    [Moderator's note: references to unsafe practices removed.]
    Sometimes it drives me mad researching this because you see a million different conflicting answers or worse, someone using the water analogy which never really sits well with me. Sorry for the basic question but hey, all questions need answers :)
     
    Last edited by a moderator: Jun 13, 2018
  2. jcsd
  3. Jun 13, 2018 #2

    anorlunda

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    That isn't quite correct. They carry the whole time in reversing directions. Think of a loop going from generator, to load back to generator. The current goes clockwise then counterclockwise around the loop.

    For safety and shock purposes, consider the hot and neutral wires the same.

    There is also the related topic of grounding, but that leads to even more millions of answers.

    There is also a third ground wire that plays no role in "normal" circumstances but you have no intuitive way to know if your wiring is in normal or abnormal condition, so the safe thing is to presume all three wires are dangerous and not spend much time imagining circumstances where they might be not dangerous.
     
  4. Jun 13, 2018 #3

    CWatters

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    +1

    You should treat neutral wires the same as live wires. You never know if someone made a mistake with the wiring.
     
  5. Jun 13, 2018 #4

    russ_watters

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    While that's fine as a blanket rule, it doesn't really answer the question and I think it would be fair and safe to do so.

    The neutral is generally less dangerous because if operating properly it has no voltage with respect to ground, by definition. With no voltage, it can't drive a current through you.
     
  6. Jun 13, 2018 #5

    anorlunda

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    No, not by definition, by convention. Do you really want kids guessing which one is neutral and trying it out?
     
  7. Jun 13, 2018 #6

    berkeman

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    Except for when Line and Neutral are reversed (I've seen this too many times in DIY wiring and other situations), and I've also gotten mild shocks from Neutral-Ground when I'm sweating and working on an electrical box far from the breaker panel (so there is a small voltage generated by the Neutral return current.

    Not to mention when a person gets confused as to which conductor is Neutral and Line. In general it's a bad practice to touch either Neutral or Line, IMO. I'm with anorlunda on this one.

    41JHnPCTf6L._SL500_AC_SS350_.jpg
     
  8. Jun 13, 2018 #7

    berkeman

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    I'm going to close this thread at this point, since it has turned into a discussion of what can shock you and what is not likely to. Amateurs and newbies can just make too many mistakes. Heck, I've made a few myself over the years, and am lucky to still be here.

    Thanks for the posts, folks.

    @david845 -- If you still have questions about this, please start a private conversation with me (click on my avatar).
     
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