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From what I understand from the NEC, bending radius for an NM cable must be at least 5x the diameter of the cable bundle (“romex”).

But how do you calculate this in a real life scenario. Is the radius of the wire below too little? Enough?

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    Good question -- 334.24 just says "the diameter of the cable" without accounting for the fact that most modern NM cables have eccentric cross-sections.... – ThreePhaseEel May 19 '20 at 1:50
  • Good question! Eagerly awaits a very code specific answer that indicates that 99% of home NM cable installations are in violation of code. :) – FreeMan May 19 '20 at 14:04
  • @freeman so you don’t see a problem with this bend? – Jeff George May 19 '20 at 20:56
  • I've found this reference (answer to 10) that suggests that the Code wants to use major diameter here, by analogy to the Chapter 9, Table 1, Note 9 cable-fill-rules, but I don't like that since flat cables are anisotropic with regards to minimum bend radius I reckon (a flat cable bends much easier if bent about one axis than the other, test it for yourself, I tried with a piece of 18/2 NISPT-2 flat cord and could barely bend it along one axis, but of course had no trouble with the other). PI time...? – ThreePhaseEel May 19 '20 at 22:37
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    @JeffGeorge -- don't laugh too hard. :) (I'm referring to submitting a Public Input to the folks who work on the NEC) – ThreePhaseEel May 20 '20 at 2:29

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