I was on a job site on a new offshore platform (still under construction) and saw several ladder cable trays that had more cables laid in that would fit in a single layer. In fact, I saw several cable tray runs where the tray was full. All the tray had a depth of 6 inches, with widths varying from 6 inches to 36 inches.
The cable was all C-L-X (type MC-HL), and Okonite describes it as having a continuous, water-impervious armor -- so that makes it a smooth sheath. Some of the cable was multi-pair or multi-triad. Some other of the cable was multi-core (3 to 7 conductors). Some of the cable contained DC circuits and some contained AC circuits. So far, I don't see where they are mixed.
Some of the cable was 15-kV (3C w/G) with a 2.5-inch diameter in a 6" x 6" tray (by itself). The latter caused concern because of bending radius. The 6 x 6 tray had an outside radius of 22.75 inches, and according to 330.24(A), the minimum bending radius is 2.5 * 15 = 37.5 inches. I suppose the cable armor is in a bind. But this is another problem.
Returning to tray fill:
Is filling cable tray with more than one layer allowed? It seems that the second layer would be anchored upon the lower layer, rather than on the tray itself. Yes, I am looking at 392.9(A)(2), and 392.9(B). Frankly, a half-filled tray does not give me a good feeling.
What are the repercussions of an overfull tray, besides reduced ampacity?
The cable was all C-L-X (type MC-HL), and Okonite describes it as having a continuous, water-impervious armor -- so that makes it a smooth sheath. Some of the cable was multi-pair or multi-triad. Some other of the cable was multi-core (3 to 7 conductors). Some of the cable contained DC circuits and some contained AC circuits. So far, I don't see where they are mixed.
Some of the cable was 15-kV (3C w/G) with a 2.5-inch diameter in a 6" x 6" tray (by itself). The latter caused concern because of bending radius. The 6 x 6 tray had an outside radius of 22.75 inches, and according to 330.24(A), the minimum bending radius is 2.5 * 15 = 37.5 inches. I suppose the cable armor is in a bind. But this is another problem.
Returning to tray fill:
Is filling cable tray with more than one layer allowed? It seems that the second layer would be anchored upon the lower layer, rather than on the tray itself. Yes, I am looking at 392.9(A)(2), and 392.9(B). Frankly, a half-filled tray does not give me a good feeling.
What are the repercussions of an overfull tray, besides reduced ampacity?