Siemens QF120GFA Single Pole Ground-Fault Circuit Interrupters, 20A, 120VAC, 1"Ground fault circuit interrupters (GFCI) are an effective means of preventing severe electrical shock. GFCIs are installed to protect areas of the home, such as the kitchen, bathroom or laundry, where electrical appliances or products may come into contact with water. designed to protect against severe electrical shock or electrocution from ground faults. Ground faults occur when the electrical current in an appliance strays outside its normal path,