current carrying conductor

[chris huckins]

Need some help determining if a control conductor is considered current carrying or not. I understand that per Table 310.15 (B) (3) (a) power and lighting ungrounded conductors are always considered to be current carrying but generally control or signal conductors are not. Is this determined locally per specific installation (gray area) or is their something definitive in the NEC stating that control and signal cables are not counted. Ex. Two sets of 3-phase, 3-wire circuits, each comprised of 4 AWG THWN copper motor branch-circuit conductors are installed in the same conduit with two 14 AWG THWN copper control circuit conductors in an ambient temperature of 30 degrees celcius. Is the allowable ampacity based on 8 current-carrying conductors or 6 current-carrting conductors?

 

[Dennis Alwon]

I believe since control circuits carry very little current then they don't need to be counted.

 

[infinity]

Take a look at 310.15(B)(3).

(3) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a
Raceway or Cable. Where the number of current-carrying
conductors in a raceway or cable exceeds three, or where
single conductors or multiconductor cables are installed
without maintaining spacing for a continuous length longer
than 600 mm (24 in.) and are not installed in raceways, the
allowable ampacity of each conductor shall be reduced as
shown in Table 310.15(B)(3)(a). Each current-carrying con-
ductor of a paralleled set of conductors shall be counted as
a current-carrying conductor.
Where conductors of different systems, as provided in
300.3, are installed in a common raceway or cable, the
adjustment factors shown in Table 310.15(B)(3)(a) shall
apply only to the number of power and lighting conductors
(Articles 210, 215, 220, and 230).

 

[petersonra]

I do not count control conductors.