NEMA ABP 5-2015 Series Ratings applies to molded case circuit breakers that are designed to protect rated conductors and in particular, ones that may be used in series-rated system. White paper shows why it is important to understand how the short circuit interrupting ratings are assigned to a combination of two or more overcurrent protective devices which are connected in series, and in which the rating of the downstream device(s) in the combination is less than the series rating.