Read 310.4, a parallel ckt is considered a single conductor so 310.16 tables apply.
You did not mention what the insulation rating is?
Where you have more than three Conductors carrying current they must be derated whether in parallel or not to prevent overheating. Except the neutral..310.15(b)(4)..
[This message has been edited by mustangelectric (edited 12-22-2004).]