Circuit breaker manufacturers publish tables providing the range of overcurrents for which specific load-side molded case circuit breakers will selectively coordinate with specific line-side circuit breakers.

• A. True
• B. False
• C. Not specified
• D. Sometimes

Answer: (A)

Selective coordination relies on pairing upstream and downstream breakers so that only the closest protective device clears a fault. Manufacturers provide coordination tables that specify the range of overcurrents (fault currents) for which a particular load-side molded case circuit breaker will coordinate with a specific line-side breaker. These tables reflect the actual trip characteristics and ratings of the devices and show the fault-current window where the downstream breaker would trip first, while the upstream breaker remains unaffected or trips only for larger faults. Having these tables helps designers choose compatible devices to achieve selective tripping and avoid unnecessary outages.