Siemens QF230A Circuit Breaker, GFCI, Type QPFB, 30 A, 2 -Pole, 120/240 V

Ground fault circuit interrupters are an effective means of preventing severe electrical shock. To protect equipment from damaging ground faults, Siemens GFCIs continuously monitor the difference in current between the hot and neutral conductors. If the electricity going to an outlet equals the current coming back from the outlet, the GFCI is dormant. If the electricity going to an outlet is greater than 5 mA than the current coming back from the outlet, the GFCI will open the circuit to stop of flow of electricity.