Ampacity adjustment over 3 conductors

[kwired]

NEC doesn’t have jurisdiction at the mine site I work at but that won’t keep me from trying to install safe according to NECs higher standards rather than MSHA.

Refereeing to NEC helps me engraving I’m memory these codes before journeyman license examination

MSHA may seemingly have lesser standards, but you also need to consider that you are in a place where training and qualifications are more specific than what is included in the across the board rules of OSHA, NFPA70 as well as 70E. Plus there is likely portions of NEC that simply never will really apply in a mine. There possibly is some requirements that may seem more stringent than NEC as well and those might offset something that otherwise looks less stringent in some ways.

 

[frs]

In Table 310.15(C)(1) (ampacity adjustments with more than one current-carrying conductor in a raceway or cable) in the 2023 code, the heading of the second column is "Percent of Values in Table 310.16 Through Table 310.19 . . ." However, in this version of the code the title of Table 310.17 is "Ampacities of Single-Insulated Conductors in Free Air. " Is there any circumstance in which Table 310.15(C)(1) would apply to the ampacities in Table 310.17, or is this just an artifact of earlier versions of the code?

 

[kwired]

In Table 310.15(C)(1) (ampacity adjustments with more than one current-carrying conductor in a raceway or cable) in the 2023 code, the heading of the second column is "Percent of Values in Table 310.16 Through Table 310.19 . . ." However, in this version of the code the title of Table 310.17 is "Ampacities of Single-Insulated Conductors in Free Air. " Is there any circumstance in which Table 310.15(C)(1) would apply to the ampacities in Table 310.17, or is this just an artifact of earlier versions of the code?

A single conductor in free air would never have an adjustment related to number of conductors in raceway, though I suppose they kind of overlooked that when they wrote that heading.

 

[wwhitney]

A single conductor in free air would never have an adjustment related to number of conductors in raceway

Obviously not, but there is also the bit about single conductors not installed in raceways not maintaining spacing. So if several "single conductors in free air" were installed together but not maintaining spacing, then the 310.15(C)(1) adjustment factors would apply to the Table 310.17 ampacities.

Of course, not sure what such an install would look like, and whether at some point you'd no longer have "single conductors".

Cheers, Wayne