Parallel Conductors and 240.4

[wwhitney]

Hello,

2014 NEC 240.4 says in part "Conductors . . . shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G)." The word parallel occurs nowhere in 240.4, and only occurs in 310.15 to tell us to count each individual conductor in a parallel installation as a current-carrying conductor for ampacity adjustment purposes. And the language that used to exist in 310.10(H) indicating that parallel conductors can be considered a single conductor (with ampacity presumably the sum of the individual conductors) is no longer present.

So given the above, what language in the 2014 NEC releases the individual conductors of a parallel installation from the basic 240.4 requirement that they be protected in accordance with their ampacity?

Thanks,
Wayne

 

[charlie b]

I tried to raise this question some years ago, to a totally "ho hum" response. We all "presume" that if you take a conductor with an ampacity of 150, and run two of them in parallel, the resulting ampacity becomes 300 amps. When that happens, we are called upon to protect this stuff at its ampacity of 300 amps, not 150. But I have never seen a code article that confirms this interpretation. I don't have a problem with using this concept, I just find it interesting that the code never tells us that we can do this.