This document provides a recommended practice for the selection@ application@ and determination of the remaining life in molded-case circuit breakers used in industrial applications. Purpose Molded-case circuit breakers are one of the most widely used circuit protection devices in low-voltage (less than 1000 V [ac]@ 1500 V [dc]) applications. In spite of their wide use in industry@ the average person specifying@ installing@ operating@ and maintaining these devices has less than a complete understanding of them. The purpose of this document is to provide people who purchase or maintain molded-case circuit breakers with a single document that includes the following information: ??How molded-case circuit breakers operate ??How to correctly size and select molded-case circuit breakers ??How to safely maintain molded-case circuit breakers ??How to determine when a molded-case circuit breaker must be replaced