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Monday, September 26, 2022
Question:
Hello CQD,
When installing cables in cable trays, Sections 392.22(A)(1)(a) and 392.80(A)(1)(c) talk respectively about "required spacing widths between cables" and "spacing not less than one cable diameter between cables." Am I correct in understanding that 392.80(A)(1)(c) is not actually a requirement [as suggested in 392.22(A)(1)(a)], but is more like a provision/condition? It seems that the code section is saying IF multiconductor cables have said spacing, THEN ampacity shall not exceed 310.14(B). Would this also suggest that if the cables are installed with that spacing, that ampacity would not be allowed to be taken from Table 310.16? And would that apply to all cables in the cable tray or just those larger than #4/0?
Any help would be much appreciated,
Curtis Syswerda
A
Answer:
Curtis,
In general, Section 392.80(A)(1) requires that the ampacity of multi-conductor cables installed in a cable tray shall be determined using Table 310.16 & Table 310.18, subject to Section 392.80(A)(1)(a)-(c) and 310.14(A)(2). If the multiconductor cables are installed in a configuration that complies with the layering and spacing found in 392.80(A)(1)(c), then the ampacity of the multiconductor cable can be calculated using 310.14(B) which requires engineering supervision but is thought to be less restrictive then Table 310.16. Annex B also provides some insight into the application of Section. 310.14(B).