trough wiring

[101010]

If you are using a trough to change from pvc (in concrete deck ) to emt (in drop ceiling), If the pipes come in one side and go out directly across, Do I have to derate? And what if you have one row on top and one row directly underneath ? None of the wires cross So the 30 wire per cross section should not come in to play right ?

 

[augie47]

I'd not closely read the derating section, and had always thought along the lines of derating only when the conductors excceded 30 in any given cross sectional area. However, I don't see that wording in 376.22(B).
IMHO, you would not need to dertate in your situation, but I can see where it might be an AHJ question as the Code simply says exceed 30 cc conductors and doesn't mention cross sectional.

 

[LarryFine]

I agree that no derating is necessary. You are running your conductors perpendicular to the cross-section of the trough, as if you had used individual boxes instead of one.

If anybody presses the issue, you can argue that the cross-section of the trough, as you are using it, is the area of the length and the depth, not the width and the depth.

In other words, the cross-section area for a 12" x 12" x 4' trough used the way you're talking about would be 4'sq, not 1'sq.

 

[infinity]

Even if derating were required to be applied to this installation 310.15(A)(2)Exception should take care of it.