Comparing test requirements for low-voltage circuit breakers

Low-voltage circuit protective devices include low-voltage power circuit breakers, insulated case circuit breakers, and molded case circuit breakers. Each of these circuit breaker types is used for particular applications, and is tested against standards that relate to those applications. In North America, low-voltage power circuit breakers are designed and tested in accordance with ANSI/UL standard 1066, which in turn refers to the series of applicable ANSI C37 standards. Insulated case circuit breakers and molded case circuit breakers are designed and tested in accordance with the UL standard 489. In this paper the standards are compared by means of tables. The standards for low-voltage power circuit breaker and the molded case circuit breaker have many common elements. As a consequence, either type of circuit breaker could be used for some applications. However, there are several significant performance differences that relate to the application of these circuit breakers. Specifically, the low-voltage power circuit breaker is normally applied upstream of the molded case circuit breakers.