Code violation for troughs

[e57]

You have a wireway with 10 conduits entering the top, each have 9 CCC.

In the back of the wireway you have 10 conduits that line up with the top.

So you have 90 CCC total, but the wires run from top conduit to back conduit

directly below it. Do you need to derate at all ? I say 'no' because nothing

crosses.

You would not have to derate the wiring in the gutter/wireway because all would be under the 30 limit - but the conductors in each conduit would be de-rated, because they each have 'more than three CCC's'... As required by 310.15(B)(2) It is one of the funnier math items in the code when it comes to the 310.16-19 tables. It also creates the misnomer of the "9 conductor rule" In most cases ambient temp is not enough to bring a circuit below commonly used circuit ratings because the values listed in 310.16 are higher, when derated at the very moderate amounts of 70% it often has no dramatic effect. (As listed in Table 310.15(B)(2)(a) up to 9 conductors are derated at 70%)

Ya know this thread is just screaming for a bunch of graphic and pictures...

 

[wirebender]

Quote:
Originally Posted by wirebender


310.15(A)(2) Selection of Ampacity Where more than one calculated
or tabulated ampacity could apply for a given circuit length,
the lowest value shall be used.
Exception: Where two different ampacities apply to adjacent
portions of a circuit, the higher ampacity shall be permitted
to be used beyond the point of transition, a distance equal
to 3.0 m (10 ft) or 10 percent of the circuit length figured
at the higher ampacity, whichever is less.

Is it me, or is this poorly worded?
__________________
Lou





I'll go for the poorly worded notion.
With the word transition, I take this to mean passing thru areas with higher temperature, and the adjustment of ampacity because of ambient temperatures.

Yes, poorly worded. I only posted it to show what boyle78 what referencing. It does seem to back up what he said IMSO. I fail to see how you can infer ambient temperature from the wording, unless you're just going by the handbook commentary example.
And what is the "point of transition"?