Bootleg ground

In building wiring, a bootleg ground is an electrical ground that is wired from the neutral side of a receptacle or light fixture in an older 2-wire home. This essentially connects the neutral side of the receptacle to the casing of an appliance or lamp. It can be a hazard because the neutral wire is a current-carrying conductor, which means the casing can become energized. In addition, a fault condition to a bootleg ground will not trip a GFCI breaker or a receptacle that is wired from the load side of a GFCI receptacle. Bootleg grounding is illegal and against code in many places. A safer alternative [NEC Sec. 406.4(D)(2)(b)] if a grounding connection is not practicable (where a local electrical code allows it) is to install a GFCI and leave the grounding terminal screw unconnected, then place a label that says "No Equipment Ground" on the GFCI and a marking that states “GFCI Protected” and “No Equipment Ground” on all downstream receptacles.

120/240 volt circuits

Before 1996, in the United States it was common to ground the frames of 120/240-volt appliances (such as a clothes dryer or oven) to neutral (grounded) conductors. This has been prohibited in new installations since the 1996 National Electrical Code upon local adoption by legislation or regulation. Existing installations are permitted to continue in accordance with NEC 250.140 Exception.