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Thread: Multiple Wires Under a Set Screw Neutral Bar

  1. #1
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    Multiple Wires Under a Set Screw Neutral Bar

    I received a service call about a 'bad breaker'. I opened the panel cause I heard an arcing noise. Part of a Square D Neutral bar was beginning to melt. Long story short. There were 3 wires under the terminal screw, 2 Grounded Conductors and a Ground. The panel is the main. What and where does the NEC state that it has to be one wire per terminal in the panel, or is that part of the UL Listing? Also what is everyones feelings about more than one wire under a terminal.
    Posts based on NEC 2011, unless noted.

    Life is tough wear a helmet, I do!

  2. #2
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    Quote Originally Posted by djcrzysounds@yahoo.com View Post
    I received a service call about a 'bad breaker'. I opened the panel cause I heard an arcing noise. Part of a Square D Neutral bar was beginning to melt. Long story short. There were 3 wires under the terminal screw, 2 Grounded Conductors and a Ground. The panel is the main. What and where does the NEC state that it has to be one wire per terminal in the panel, or is that part of the UL Listing? Also what is everyones feelings about more than one wire under a terminal.
    Suppose to be listed for more than one under one terminal. Theoretically it will work with more than one, same as a splice! Not saying it's ok.
    VA Master Electrician

  3. #3
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    Cant have more than one grounded conductor under a screw hole.408.41

  4. #4
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    Quote Originally Posted by lucky1974 View Post
    Cant have more than one grounded conductor under a screw hole.408.41
    True.

    Multiple EGCs are allowed under one screw, provided the panel is rated for it. Most modern load centers that I am aware of will allow 2 or 3 #14s/#12s.
    John from Baltimore
    "One Day at a Time"
    Responses based on the 2008 NEC

    If you can stay calm, while all around you is chaos...then you probably haven't completely understood the seriousness of the situation

  5. #5
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    Quote Originally Posted by djcrzysounds@yahoo.com View Post
    I received a service call about a 'bad breaker'. I opened the panel cause I heard an arcing noise. Part of a Square D Neutral bar was beginning to melt. Long story short. There were 3 wires under the terminal screw, 2 Grounded Conductors and a Ground. The panel is the main. What and where does the NEC state that it has to be one wire per terminal in the panel, or is that part of the UL Listing? Also what is everyones feelings about more than one wire under a terminal.
    When you would unwire one circuit and attempt to remove the corresponding EGC, the equipment still in service would be unprotected while the wire to be abandoned is removed. In the case of neutrals it is even a bigger problem as you would need to shutdown the 'other' circuit as well. So as a general rule one EGC and neutral per set-screw.

  6. #6
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    Quote Originally Posted by weressl View Post
    So as a general rule one EGC and neutral per set-screw.
    Do you mean "one EGC or neutral"?
    John from Baltimore
    "One Day at a Time"
    Responses based on the 2008 NEC

    If you can stay calm, while all around you is chaos...then you probably haven't completely understood the seriousness of the situation

  7. #7
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    Quote Originally Posted by JohnJ0906 View Post
    Do you mean "one EGC or neutral"?
    Yes and no, yes and no, yes and no. One EGC per each ground set screw and one neutral wire per each neutral set screw. Certainly don't suggest to terminate the EGC under the neutral set screw or vice versa.......

  8. #8
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    Quote Originally Posted by weressl View Post
    When you would unwire one circuit and attempt to remove the corresponding EGC, the equipment still in service would be unprotected while the wire to be abandoned is removed. In the case of neutrals it is even a bigger problem as you would need to shutdown the 'other' circuit as well. So as a general rule one EGC and neutral per set-screw.
    I shut down the whole panel prior to removing wiring from busbars....
    85deg. an Sunny today.

  9. #9
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    Quote Originally Posted by macmikeman View Post
    I shut down the whole panel prior to removing wiring from busbars....
    From the neutral or ground bus? Really? How do you justify that.

  10. #10
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    Quote Originally Posted by weressl View Post
    Yes and no, yes and no, yes and no. One EGC per each ground set screw and one neutral wire per each neutral set screw. Certainly don't suggest to terminate the EGC under the neutral set screw or vice versa.......
    While you make a good point about why it would be a good practice to use one screw per EGC, the code and the listing does not normally require this. For most panel terminal bars the listing permits more than one EGC per screw.
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

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