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Thread: wire bending radius

  1. #1
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    wire bending radius

    Is there a code that regulates minimum bending radius for # 12 thhn? I recently had a home inspection done and the "inspector" stated that the wires should have a sweeping bend as opposed to a neatly trimmed bend. He said this was due to heat build up. I am a certified thermographer as well as an electrician and I have never recorded a heating issue due to bend radius on # 12 wires at 120/240 volts. I do not have access to my nec book at this time. I have searched previous threads and could not find a definite answer.

  2. #2
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    There is no minimum bending radius for common single conductors. The NEC list 'bending space at terminals' but that is not the same thing as bending radius.
    Just because you can, doesn't mean you should.

  3. #3
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    Quote Originally Posted by Bennington View Post
    Is there a code that regulates minimum bending radius for # 12 thhn? I recently had a home inspection done and the "inspector" stated that the wires should have a sweeping bend as opposed to a neatly trimmed bend. He said this was due to heat build up. I am a certified thermographer as well as an electrician and I have never recorded a heating issue due to bend radius on # 12 wires at 120/240 volts. I do not have access to my nec book at this time. I have searched previous threads and could not find a definite answer.
    that, is just silly.

    it's more of an appearance thing than anything else.

    solid wire looks better when squared off, and, imho,
    stranded wire looks better when shwooped into place.
    it's a personal preference, altho neat, tidy, and consistent
    seems to count for a lot.

    to get heating in a wire as a result of a tight bend would
    be from what? inductive reactance? what frequency
    would the AC have to be at to make a 90 bend heat?
    ~New signature under construction.~
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  4. #4
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    Quote Originally Posted by Bennington View Post
    Is there a code that regulates minimum bending radius for # 12 thhn? I recently had a home inspection done and the "inspector" stated that the wires should have a sweeping bend as opposed to a neatly trimmed bend. He said this was due to heat build up. I am a certified thermographer as well as an electrician and I have never recorded a heating issue due to bend radius on # 12 wires at 120/240 volts. I do not have access to my nec book at this time. I have searched previous threads and could not find a definite answer.
    Just pure nonsense.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  5. #5
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    Thanks for your responses. I can't wait to see the rest of the report. LOL

  6. #6
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    Ask him if he would rather you use one of these on # 12 wire

    http://www.toolfetch.com/greenlee-79...wJ4aAls18P8HAQ

  7. #7
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    Hmm...well not 100% nonsense from a manufacturers perspective (But Close). Yes, the NEC makes no reference to the maintained bending radii of individual conductors except at terminations. However, many manufacturers do provide guidance on the level of excessive bending that is recommended to their products. IN many cases we will say to maintain a 5, 8 or even 10 times the diameter of the wire bend in order to lessen the potential elongation damage to the conductor itself.

    Point is, while it is not an NEC thing it can and of course often overlooked without incident which is something a manufacturer may be able to provide guidance on. As for testing, a copper conductor/wire that is excessively bent to a point where the copper material elongates out can effect the conductivity of the product at that given point, resistance to current flow can cause a thermal heat rise in a damaged conductor/wire.....but then again in our tests we always test the products well beyond what would be expected in the field.

    With regards to the Home Inspector, I would always guard against them making such a statement because again the bends to cause any possible issue would be way more severe than you would see in a normal electrical panel with regards to 12 AWG...and they simply do not have the same research available to make such a statement.

    As for our results....you can agree or disagree or even say we are full of ****...but in reality we have the advanced equipment to test this and have as part of our ongoing R & D. Again, it is hard for a normal installation to create an issue with this so this is why the NEC doesn't deal with this issue. If the manufacturers really felt it was a perceived safety issue we would most certainly submit a PI on it to NFPA 70 but alas it is not a concern so after reading all this....its about 98% nonsense based on the context of the OP's and Home Inspectors statement....but not 100% nonsense...
    *All code responses are based on the 2017 National Electrical Code[NEC]

  8. #8
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    I think the only limitation would be to stop bending before the insulation is damaged.
    Cheers and Stay Safe,

    Marky the Sparky

  9. #9
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    Quote Originally Posted by MasterTheNEC View Post
    ...the NEC makes no reference to the maintained bending radii of individual conductors except at terminations.
    The NEC is concerned with the amount of space provided at the termination, it makes absolutely no reference to the radii.

    Quote Originally Posted by MasterTheNEC View Post
    ...manufacturer may be able to provide guidance on...
    When I assembled UL508A panels, we made our bends using pliers, the tighter the radii the better.
    I recall there was a situation where even a hammer was involved to...
    Just because you can, doesn't mean you should.

  10. #10
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    Quote Originally Posted by jim dungar View Post
    The NEC is concerned with the amount of space provided at the termination, it makes absolutely no reference to the radii.


    When I assembled UL508A panels, we made our bends using pliers, the tighter the radii the better.
    I recall there was a situation where even a hammer was involved to...
    LOL.....well all I can say is at that point You Own It....lol and I agree the NEC is silent on the subject as previously stated.
    *All code responses are based on the 2017 National Electrical Code[NEC]

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