“Motor contribution” is only used in 240.86(C) in the National Electrical Code (NEC), but the NEC does not define it anywhere. A full explanation of this important electrical application is located in other publications, such as fuse and circuit-breaker protection books and articles.
Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC), Jim will help you solve it. Questions can be sent to firstname.lastname@example.org. Answers are based on the 2014 NEC. Pull boxes for communications cable