jdrummond
Member
- Location
- Portland, OR, USA
I have a design with more than one layer of maple cable blocks in fiberglass ladder cable tray (see example illustration below). The cable blocks keep the single-conductor 500 kcmil cables spaced at more than one diameter horizontally and vertically. This allows space for air to circulate around the cables.
2011 NEC 392.80(A)(2)(c) allows us to use the higher "free air" ampacities of Table 310.15(B)(17), if you have a single layer of cables and horizontal spacing between them is more than one cable diameter. However, this section does not address vertical spacing.
Can I treat each layer of cable block as a separate cable tray and use the "free air" ampacity?
Is there another section of code that addresses this?
2011 NEC 392.80(A)(2)(c) allows us to use the higher "free air" ampacities of Table 310.15(B)(17), if you have a single layer of cables and horizontal spacing between them is more than one cable diameter. However, this section does not address vertical spacing.
Can I treat each layer of cable block as a separate cable tray and use the "free air" ampacity?
Is there another section of code that addresses this?
