wire bending radius

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Bennington

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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.
 
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.
 
Bennington said:
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.
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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?
 
Bennington said:
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.
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Just pure nonsense. :roll:
 
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...;)
 
MasterTheNEC said:
...the NEC makes no reference to the maintained bending radii of individual conductors except at terminations.
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The NEC is concerned with the amount of space provided at the termination, it makes absolutely no reference to the radii.

MasterTheNEC said:
...manufacturer may be able to provide guidance on...
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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...
 
jim dungar said:
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...
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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.
 
Follow manfactures specs.

Follow manfactures specs.

I just installed a Siemans panel and the instructions said to not make tight bends and also not to run down and back up leaving excess wire. It actualy showed a picture of a panel with down and up wires bent to a 90 with a red x thru it. Then a picture of a panel with the feed and circuits sweeping in to the breakers. Of coarse I threw them away or i would of posted them.

Cowboy
 
MasterTheNEC said:
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.
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This is misleading when referred to as "conductor diameter". Copper is a conductor. PVC and nylon are not conductors.


Does "conductor diameter" in this context mean overall wire diameter including insulation, or does it mean diameter of the conductive core of the wire?
 
Oh yes....as usual my efforts are to mislead. Because that's what I do....LOL....nevermind I probably am lying anyway...Good Luck.

PS....incorrect....assumption ...it's wire.....CU is a conductor or conductive material but then again your intent is to tit for tat...so I will just let you win....less effort.

Comments based on the 2017 National Electrical Code.
 
Thanks again for the responses. After reading the post from master it reminded me of several machine installs that had pre wired control panels with bends much sharper than the ones in my panel. Hopefully this means he was stretching to find something! Lol
 
just the cowboy said:
I just installed a Siemans panel and the instructions said to not make tight bends and also not to run down and back up leaving excess wire. It actualy showed a picture of a panel with down and up wires bent to a 90 with a red x thru it. Then a picture of a panel with the feed and circuits sweeping in to the breakers. Of coarse I threw them away or i would of posted them.

Cowboy
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:lol:

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If bent wires were a hazard, every single switch and receptacle box in America would be shooting flames from it right now. Now, bend the heck out of catx, coax, or fiber it may not be as forgiving. The bending radius of small gauge copper cant be less than wrapping it around a screw terminal. Pretty hard to bend it that badly, tho with AL I do try to baby it as much as possible and not rebend it too much.
 
JFletcher said:
If bent wires were a hazard, every single switch and receptacle box in America would be shooting flames from it right now. Now, bend the heck out of catx, coax, or fiber it may not be as forgiving. The bending radius of small gauge copper cant be less than wrapping it around a screw terminal. Pretty hard to bend it that badly, tho with AL I do try to baby it as much as possible and not rebend it too much.
Click to expand...

Good point, often in a device box you will have one or two tight 180 degree bends in the conductors when folding them in neatly.
 
This was a common method of connecting wires to boards 50 years ago:

wirewrap_fig6.jpg
 
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