These requirements cover ground-fault circuit-interrupters intended for use only in alternating-current circuits wherein one of the wires is grounded in accordance with the National Electrical Code. These devices are intended for use on 120 Vac or 120/240 Vac, 60 Hz circuits. These requirements do not cover ground-fault circuit-interrupters intended for use in circuits served by a transformer having windings wholly insulated from each other. A ground-fault circuit-interrupter as covered by these requirements is a device whose function is to interrupt the electric circuit to the load when a fault current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the supply circuit.
Retrieved from Dianyuan on 11-15-2013