I saw something called speedway non-metallic support system for cables at an IAEI meeting recently. It is a system of cable "rings" meant to be mounted under the joists in a residental basement. It also had a solid plastic "cover" that snapped on below, to enclose both sides and the bottom of the rings and hence the cables run through the rings.
The manufacturer's rep told me that no derating of conductors was required. The glossy he handed out said that you could, for example, put up to 23 12-3/G NM-B (for a max of 40% fill).
I'm trying to figure out how this is covered in the NEC. The best guess is that 392.11(A) applies. It refers back to 392.9. I believe that 392.9(F) applies and that speedway's 40% fill is more or less compliant.
Now back to 392.11(A): (1) says derating applies only to cables with more than 3 current carrying conductors [speedway only lists 3 or less conductor cables], (2) talks about covers which complete the enclosure by covering the top [no cover for speedway], and (3) single layer and properly spaced [not mentioned in speedway literature].
What I'm trying to understand is this: does the 392.11(A)(1) no derating required for less that 3 apply even though 392.11(A)(3) requires a single layer and spacing is violated?
