Patent ID: 7978447

Claim:
A method of preventing hazardous conditions at an electrical safety device by preventing the delivery of AC power to an AC output of the safety device until a safe load is connected to the device and turned on, the method comprising: providing an electrical safety device having an AC input and an AC output; receiving an AC line voltage at the AC input of the safety device; providing a relay between the AC input and the AC output that electrically connects the AC line voltage received at the AC input to the AC output, that disconnects the AC line voltage from the AC output, and that is initially in a state that disconnects the AC line voltage from the AC output; providing a DC low-voltage load testing voltage to the AC output; measuring a load impedance at the AC output with the load testing voltage; providing a DC low-voltage ground fault testing voltage to the AC output; switching the relay to connect the AC line voltage to the AC output only when the load impedance measured is higher than a lower reference impedance and is lower than a higher reference impedance and only when no ground fault exists at either power terminal of the AC output; measuring a load current passing to the AC output when the AC line voltage is connected to the AC output; and switching the relay to disconnect the AC line voltage from the AC output when the load current drops below a minimum reference current.