What is the difference between 80% and 100% rated circuit breakers?

    Circuit breakers are designed to carry 100% of their rated current, yet the National Electric Code (NEC) dictates an 80% application.  Loading at 80% is only applicable when continuous loads are involved.  The NEC defines a continuous load as a load where the maximum current is expected to continue for 3 hours or more.  Circuit breakers can be sized at 100% of their rating for any non-continuous load application.  The NEC does not recognize assemblies that are listed for operation at 100% of their rating for continuous loads unless the assembly is marked by the manufacturer to meet the UL standards.  These UL standarads specify minimum circuit breaker enclosure sizes and venting requirements.  This involves additional testing to verify that the additional heat generated by 100% continuous loading conditions is safely dissipated.  All standard rated circuit breakers are subject to NEC sizing rules.

What are the common accessories available for circuit breakers?

 Shunt trip   trips a circuit breaker remotely so that the equipment can be stopped rapidly
 Auxiliary Contacts  used to provide command or signal outputs, interlocking with other switches, and for remote indication of the switching state
 Motor Operators  allows circuit breakers to be tripped (opened) or closed under remote control, may be part of the automatic transfer switch system for standby power