Can multi-channel surface metal raceways be considered as separate raceways?

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noilliz

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I'm looking at some of the larger Wiremold surface metal raceway (SMR) products which feature two or more separated channels inside. Specifically the ALA4800 product where each channel has an area of 6.04in^2. Here is a picture of the cross section:

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According to NEC 2011 386.22, such a raceway would be allowed to have 30 current-carrying conductors without derating assuming the 20% fill factor is not exceeded. Basically, such a raceway is considered under the same rules afforded to wireways (376.22), which I am more familiar with.

My real question is whether each compartment / channel of these raceways can be considered its own raceway - i.e. can each channel have 30 CCCs without derating? Obviously the two sub-channels are thermally coupled as they share a single aluminum extrusion, but that extrusion still has 79% of the external surface area of two separate extrusions of the same size. Assuming a 20% fill and the normal horizontal orientation of the SMR (rotated 90deg from this illustration), conductors in each channel would still be separated by 2.4"

I'm not seeing anything in the NEC specifying the required spacing between raceways other than 310.15(B)(3)(a)(5)(b) which says "Spacing between conduits, tubing, or raceways shall be maintained" which my NEC 2011 Handbook interprets as being necessary due to fastening methods, not thermal considerations. I mention this because if I am allowed to put two single-channel SMRs right next to each other, it is functionally the same as this single extrusion.
 
I received some answers back from Legrand:

the capacity tables just state the maximum number of wires of any particular size the raceway is UL listed for. If the conditions in 386.22 are not met, the derating requirements in the NEC take effect.

The multi-channel issue, as you noted, is not directly addressed by the NEC and therefore is subject to interpretation. Per the NEC, the local AHJ is responsible for providing that interpretation. It has been my experience that AHJs generally consider the system to be one raceway regardless of how many sub-channels it's divided into. However, you will need to consult with the AHJ for the project you are working on as they may have a different opinion.[FONT=&quot]
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Looks like people have not had much luck convincing AHJs that these are effectively equivalent to two SMRs. I guess most people just use these larger products to do power / data in the two channels, or for the extra room inside for wiring devices.
 
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