Type W cable

[Twoskinsoneman]

Looking throught Table 400.5 (b) Ampacities for Type W cable.
Why do the ampacities seem so high. I can use a Type W cable with only two CCC up to 115 amps at 75?C
Table 310.16 value is only 85 amps. What gives?

 

[winnie]

Given that code says what it says without saying why it says it, we can only guess If you want to know why, you will have to delve into the history of the CMP.

My guesses:
1) Article 400 applications are exposed, not buried in walls or insulation. This means better cooling and thus higher ampacity.
2) Article 400 applications are exposed and subject to both physical wear and visual inspection. Greater amounts of insulation degradation could be tolerated because it would be detected and corrected .

-Jon