Are circuit breakers (CBs) that are not marked with an interrupting rating rated at 5000A?

The assertion that circuit breakers (CBs) that are not marked with an interrupting rating are rated at 5000A is not supported by standard electrical practices and codes. In fact, circuit breakers must be marked with their interrupting capacity, which indicates the maximum amount of fault current they can safely interrupt without causing failure or unsafe conditions. An unmarked circuit breaker does not imply a default rating; rather, it could signify that the device's interrupting capacity is undefined or is below the commonly accepted standards for safety.

Therefore, saying that all unmarked circuit breakers are rated at 5000A is misleading. Ratings can vary widely based on manufacturer specifications and applicable standards, and thus, it's essential to check the manufacturer's documentation for the specific interrupting rating of each circuit breaker. Thus, the statement itself is incorrect leading to the conclusion that the provided answer is inaccurate.