Circuit breakers covered by this specification are intended primarily for use in the protection of electronic circuits and should be used where starting inrushes of transient overloads are neither heavy nor prolonged and the equipment must have relatively fast protection. These circuit breakers should not be used in circuits (e.g., primary power circuits of electric systems) whose short circuit current potential is greater than the interrupting capacity of the breaker unless the circuit is properly protected by other means.

Circuit breakers should continuously carry normal load current; however, the value chosen should be the lowest rating that will not open the circuit breaker inadvertently. The following factors should be considered in selecting the proper current rating and time delay curve of a circuit breaker:

a. The average (steady state) conditions of the load.

b. The initial start-up current and duration of the current of the equipment to be protected.

c. Transient overloads and their duration.

d. Comparison of the time delay characteristics of the circuit breaker with the time current characteristics (including starting or overload surges) of the equipment, component, or wire.