Layered cable derating factors

[abqjfcee]

I can't find in the code where the derating factors are located for multi layer runs or specifically cable on a reel. (SO cord, temp ratings, etc.)

I can find derating factor info on the web, just not in the code. Anyone know where this info is located in the 2008 code?

Does the code point to vendor derating info? (Same approach as in mining...?)

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[charlie b]

I don't quite understand the question. Are you talking about layering cables on top of one another within a cable tray?

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[abqjfcee]

Layered Cable

Layered Cable

This is specifically for a 300' reel of cable that a user does not want to completely unroll/unspool to use. They also do not want to increase wire size (a different issue).

My concern is that the cable should be treated similar to a cable tray as the inner layers will not be able to dissipate heat and may overheat increase in resistance, drop more voltage, etc. All of this bad.

Is there a code section that can be applied in this instance?