The OCPDs protecting circuits for supervised fire pumps are selected to ___.

The OCPDs protecting circuits for supervised fire pumps are selected to ___.

• A. carry LRC for an indefinite period
• B. permit the pump to burn up before the OCPDs open
• C. both a and b
• D. neither a nor b

Answer: (C)

The main idea is that protection for a supervised fire pump must accommodate the motor’s starting surge so the pump can actually start and run. Motors draw a much higher current when they start (locked-rotor current), and if the overcurrent protective device trips during that transient, the pump won’t start when it’s needed for a fire event. So the protection is chosen to carry that starting current for the necessary brief period and to allow the pump to come up to speed before any protective action would interrupt the circuit. In a supervised fire-pump circuit, reliable start and run are essential, so the device is selected to tolerate the initial inrush and then protect the circuit once the motor is running.

The main idea is that protection for a supervised fire pump must accommodate the motor’s starting surge so the pump can actually start and run. Motors draw a much higher current when they start (locked-rotor current), and if the overcurrent protective device trips during that transient, the pump won’t start when it’s needed for a fire event. So the protection is chosen to carry that starting current for the necessary brief period and to allow the pump to come up to speed before any protective action would interrupt the circuit. In a supervised fire-pump circuit, reliable start and run are essential, so the device is selected to tolerate the initial inrush and then protect the circuit once the motor is running.