Single Pole Combo Arc Fault Circuit Breaker 20 Amp"SQUARE D" FAULT CIRCUIT BREAKER QO, 20A Single Pole Combo Arc Fault Circuit Breaker Provides Standard Overload & Short Circuit Protection 3 4" Format For Us In QO Brand Load Centers 120 240 Vac, 10,000 A. I. R., UL CSA Listed Meets 2008 National Electrical Code For Series & Parallel Arc Fault Protection. The Square Dr Arc D tectr Arc Fault Circuit Interrupter (AFCI) is designed to detect arcs that are caused by damaged, aged or improperly used wires