Definition of "conductor" / paralleling

[aries]

While studying tables for conductor count in a conduit I'm trying to determine the definition of "conductor" as used in these tables.

Without derating the table calls out "not more than three current carrying conductors". Now, if I run quantity two 250mcm wire paralleled to carry one phase of a three phase setup -- would this be considered one current carrying conductor comprised of two 250mcm wire or would it be considered two distinct current carrying conductors? I think the answer is the former -- two paralleled wires are considered one conductor.

And, to follow, would I then be able to run six 250mcm "wires" (2 paralleled for each phase) through the apropriate conduit without derating. I think the answer to this one is yes, I could run all three phases (three conductors) comprised of a total of 6 wires paralleled two per phase.

Lastly, related to this.. in a 3 phase 4 wire system.. is the neutral considered a "current carrying conductor" for the purposes of this rule? I think the answer is yes.

Thanks
-J

 

[raider1]

Take a look at 310.15(B)(2)(a).

As for the neutral take a look at 310.15(B)(4)

Chris

 

[augie47]

at least you are consistiant
each conductor is counted...two parallel conductors = two conductors
neutral are counted per 310.15 (B) (4). In your case, the neutral would not count
unless the load is nonlinear.

 

[infinity]

This was cleared up in the 2005 NEC with the additional sentence at the end of 310.15(B)(2)(a) as Chris mentioned.

 

[tom baker]

Now, if I run quantity two 250mcm wire paralleled to carry one phase of a three phase setup -- would this be considered one current carrying conductor comprised of two 250mcm wire or would it be considered two distinct current carrying conductors? I think the answer is the former -- two paralleled wires are considered one conductor.
-J

The 2005 clarified that conductors in parallel are considered two, not one. See 310.4 (D). The arguement was used before the 05 NEC that two paralled wires are condsidered one.
There is a difference between 2 sets in parallel in one conduit and two conduits. Run the ampacity calcs to find out.