building wiring Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure. Wiring is subject to safety standards for design and installation. Allowable ...

installed with separate neutral and protective ground bonding conductors (a TN-S network), a bootleg ground (or a false ground) is a connection between the neutral side of a

receptacle Receptacle may refer to: Biology * Receptacle (botany), a plant anatomical part * Seminal receptacle, a sperm storage site in some insects Electrical engineering * Automobile auxiliary power outlet, formerly known as ''cigarette lighter recep ...

or light fixture and the ground lug or enclosure of the wiring device.

Description

A bootleg ground connects the neutral side of the receptacle to the conductive casing of an appliance or lamp. This can be a hazard because the neutral wire is a current-carrying conductor, which means the exposed casing can become energized. In addition, a fault condition to a bootleg ground will not trip a

GFCI A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) is an electrical safety device that quickly breaks an electrical circuit with leakage current to ground. It is to protect equip ...

breaker, nor protect a receptacle that is wired from the load side of a GFCI receptacle. Before 1996, in the United States it was common to ground the frames of large 120/240-volt permanently-connected appliances (such as a

clothes dryer A clothes dryer, also known as tumble dryer or simply dryer, is a powered household appliance that is used to remove moisture from a load of clothing, bedding and other textiles, usually shortly after they are washed in a washing machine. Many d ...

oven upA double oven A ceramic oven An oven is a tool which is used to expose materials to a hot environment. Ovens contain a hollow chamber and provide a means of heating the chamber in a controlled way. In use since antiquity, they have been use ...

) to neutral conductors. This has been prohibited in new installations since the 1996

National Electrical Code The National Electrical Code (NEC), or NFPA 70, is a regionally adoptable standard for the safe installation of electrical wiring and equipment in the United States. It is part of the National Fire Code series published by the National Fire Pro ...

(upon local adoption by legislation or regulation). Existing installations are permitted to continue in accordance with NEC 250.140 Exception.

Correct-polarity bootleg ground

In the less-dangerous instance of a bootleg ground, a short wire jumper is connected between the bonding screw terminal (usually colored green) on a NEMA 5-15R or 5-20R outlet to the neutral (a.k.a. grounded conductor, colored white according to code) or directly to the white neutral wire via a pigtail. This practice is a NEC code violation, but a standard 3-lamp

receptacle tester An electrical outlet tester, receptacle tester, or socket tester is a small device containing a 3-prong power plug and three indicator lights, used for quickly detecting some types of incorrectly-wired electrical wall outlets or campsite supplies ...

will report the outlet as correctly wired.

Reverse-polarity bootleg ground

In the very-dangerous instance of a reverse polarity bootleg ground, the hot and neutral wires have been connected to the opposite terminals, and a jumper or pigtail connection is made between the green bonding screw terminal and what is believed to be the neutral circuit. But because the wiring has been crossed at some point, the hot 120-volt wire is now connected directly to the ground on the receptacle, placing low-impedance live voltage on all grounded parts of all equipment plugged into that outlet. This hazardous connection allows people to come into contact with a deadly voltage with a current path back to the source (the power transformer) that will not trip either a normal

circuit breaker A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by an overcurrent or short circuit. Its basic function is to interrupt current flow to protect equipment and to prevent the risk ...

, a GFCI, nor an AFCI quickly enough to prevent electrocution.

Safer alternatives

If a safe equipment ground path is not provided via the existing cables installed within the building, they ideally should be replaced with new cabling which includes a safety ground conductor. A safe alternative (where local electrical code allows it), permitted by recent editions of the National Electrical Code EC Sec. 406.4(D)(2)(b)if a grounding connection is not practicable, is to install a

and leave the grounding terminal screw unconnected. This is permitted if a permanent label is installed that says "No Equipment Ground" on the GFCI, and a label that states “GFCI Protected” and “No Equipment Ground” is placed on all downstream receptacles.

Other countries

West Germany banned bootleg grounding in 1973, although it was common practice before and can still be found in older installations.{{cn, date=August 2021 In Finland, using neutral as a ground conductor was a common practice until 1989. After that, a thicker PEN-wire was used as both ground and neutral until it was banned in 2007.SFS 6000 Muutokset 2007 Sähkö ja teleurakoisijaliitto STUL ry Esa Tiainen, Arto Saastamoinen 2007 p. 22

References