I am putting in some under-cabinet lighting, hard wired. At one particular light it will be easier if I can put a 90 degree angle in the romex as it comes out of the knockout on the light housing. I'm pretty sure this is wrong, but can anyone tell me why? (if it is wrong)
Will the sharp angle overheat the wiring? Or cause premature failure of the insulation?
Thanks for any tips.
It depends on just how sharp the bend is.
"Bends in cable shall be made, and other handling shall be such, that the protective coverings of the cable will not be damaged, and no bend shall have a radius less than five times the diameter of the cable." [National Electrical Code, Article 336-14]
Both. If the bend is so sharp as to kink the conductor, there is indeed the possibility of creating a hot spot at the kink. This could also damage the insulation.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
Oh!, MG. How dare you question the NEC Gods?
:::::))))))))))))))
Colbyt
Thanks for the info Doug.
Interesting response. Romex cable is about rectangular, let say 1/4" by
1/2" more or less. The bare wire is 1/16" and the insulation OD about 1/8", dimension are eyeballed from memory so let's not get particular about it. Which of these dimensions need to be multiplied by 5 to obtain the minimum bending radius?Unless the answer is "the bare wire diameter", every outlet/switch box I ever opened had this rule violated multiple times.
Appreciate some clarification.
MG
The Code says "five times the diameter of the cable" which clearly refers to the entire assembly, not individual conductors. This would seem to mean (using your approximate dimensions above) a minimum radius of 1.25" if bent forward/backward, and 2.5" if bent sideways.
AFAIK, this doesn't apply inside boxes where the cable sheath has been stripped off.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
Thanks, that clears it.
MG
Use stranded wire and you wound have to worry about this. I really really hate romex.
This rule sounds like a left-over from the days when Romex was paper wrapped and then covered with a braided loomex material which was then tarred and/or waxed - messy stuff to remove. If you bent the wire sharply the outer material could split exposing the paper wrapping around the inner insulated wires. Now that they are covered in a vinyl material this doesn't happen. However, it still doesn't look good if you create a sharp bend.
Might make the electrons dizzy. OTOH, unless you reallly make a sharp 90, I can't imagine it hurting much. Might tend to weaken the copper wire.
replying to Stormin Mormon, Dovetail Guy wrote: In my experience in the field, They seem to be making romex less robust. We had romex short out when bent too tight. The insulation on the conductors breaks and you got copper to copper. I think the technology in the manufacturing process allows them to make the insulation thinner. It happened with 12/2, 14/2 and 10/3.
Maybe this would have helped avoid damage.
"334.24 Bending Radius. Bends in Types NM, NMC, and NMS cable shall be so made that the cable will not be damaged. The radius of the curve of the inner edge of any bend during or after installation shall not be less than five times the diameter of the cable."
If Stormie replies to you, tell him the AHR guys said "Hi" Seems like his wi-fi is not connecting.
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