Look at the diagrams that Roger posted. Any current flowing in a hot wire has to be balanced somewhere. If each hot wire has its own separate neutral, then the current flowing in that neutral _must_ be equal to the current flowing in the hot. Therefore if the hot is counted as a current carrying conductor, the neutral must also be counted.
_Shared_ neutrals under _some_ conditions need no be counted as current carrying conductors. This is because the current flow in the hot will be balanced by the current flow in the opposite hot.
Remember: the current flow in a string of series connected elements is always the same everywhere.
In your example, there would be 8 current carrying conductors.
While I agree with the ideas posted so far I think the NEC says you do not need to count the grounded conductor as a current carrying conductor for the purpose of derating in this instance. The text of the code reads:
310.15 (B)(4)(a) A Neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(B)(2)(a)
I interpret this to read: "One hot and one neutral count as 1 CCC when applying 310.15(B)(2)(a)"
A multi-wire circuit would require counting the grounded conductor according to 310.15(B)(4)(b&c)
Have I missed the boat? What do you guys think?
[This message has been edited by Local (edited 09-18-2005).]
Local it is talking about at least a 3-wire ciruit. "...unbalanced current from other conductors of the same circuit"
But I think there's something wrong with the wording here. I think it should be balanced current! Otherwise it is a current carrying conductor, right? At least in single phase it would be. Hmmmm. It's late, and I need beer.
Mark Heller "Well - I oughta....." -Jackie Gleason