North American and IEC standards for circuit breakers

Which standards are appropriate for molded-case circuit breakers in North America-North American or International Electrotechnical Commission (IEC) standards? Though IEC standards are generally international, they are not adopted worldwide. It is not always recognized that the National Electrical Code (NEC) is also international. The product standards for molded-case circuit breakers in the three North American countries are largely identical to each other, but not equivalent to the IEC standards for circuit breakers. These product standards could also be considered international, at least in content. How does one compare Underwriters Laboratories (UL) and IEC standards for circuit-breaker products? One way is to compare the details of one standard to the corresponding details of the other as would be necessary to convert an existing product designed to one standard to the other. Square D Company did such a comparison in both directions. The process was tedious and the results not practically applicable in specifying a product for a given application. However, the exercise did reveal some very useful points related to the products. This article discusses some of these points to provide an overview of product differences.