Which statement about instantaneous-trip breakers is true?

Which statement about instantaneous-trip breakers is true?

• A. They can only be used as branch-circuit OCPD for lighting
• B. They can be installed as part of listed combination with a motor controller
• C. They cannot be used with a motor controller
• D. They always trip instantly for any overload

Answer: (B)

Instantaneous-trip breakers use a magnetic mechanism to trip immediately when a fault current spikes, which is essential for fast short-circuit protection. They can be part of listed motor-controller assemblies, meaning the breaker is included in a manufacturer’s listed combination with a motor controller and tested as a unit. This ensures proper coordination and safe operation in motor circuits. They’re not limited to lighting branch circuits, and they’re not restricted from being used with motor controllers when the listing supports it. Also, they don’t trip instantly for any overload—their instantaneous trip action applies to high fault currents, while normal overloads typically trip through the thermal (time-delayed) element. So the correct statement is that they can be installed as part of a listed combination with a motor controller.

Instantaneous-trip breakers use a magnetic mechanism to trip immediately when a fault current spikes, which is essential for fast short-circuit protection. They can be part of listed motor-controller assemblies, meaning the breaker is included in a manufacturer’s listed combination with a motor controller and tested as a unit. This ensures proper coordination and safe operation in motor circuits. They’re not limited to lighting branch circuits, and they’re not restricted from being used with motor controllers when the listing supports it. Also, they don’t trip instantly for any overload—their instantaneous trip action applies to high fault currents, while normal overloads typically trip through the thermal (time-delayed) element. So the correct statement is that they can be installed as part of a listed combination with a motor controller.