Cheater plug
Encyclopedia
A cheater plug, AC ground lifter or three-prong/two-prong adapter is an adapter that allows a NEMA 5-15P grounding
-type plug (three prongs) to connect to a NEMA 1-15R non-grounding receptacle (two slots). The use of such an adapter avoids the need to replace receptacles, but is potentially hazardous, if the grounding tab is not actually connected to electrical ground. An alternative identified in the U.S. and Canadian electrical codes is to replace the outlet with a GFCI breaker outlet.
Cheater plugs were previously available with a short flexible grounding wire rather than a screw tab. This allows use of the second duplex outlet that does not have a faceplate screw in the correct location for the screw tab. The grounding wire would be wrapped around the adapter to reach the faceplate screw. However, this ground-wire style of cheater plug was discontinued when it was noted that a loose unattached grounding wire could by accident become inserted into the "hot" blade socket of a nearby outlet, potentially leading to electrocution.
Cheater plugs are also used to break ground loops
in audio systems. This practice has been condemned as disregarding electrical safety. An alternative is to use an isolation transformer
made specifically for this purpose.
mandated three-prong plugs on small appliance
s for safety. At that time, only half of the receptacles in U.S. homes were three-prong. Wiring in most homes did not include a grounding wire. The screws and outlet boxes were either connected to the neutral, or connected to nothing. Only in rare jurisdictions where non-metallic cable was prohibited, and armored cable required, do cheater plugs work as intended. In 1971 the U.S. National Electrical Code (NEC) required grounded receptacles in all locations of the home (effective January 1, 1974).
and video fields, the cheater plug has been identified as a serious safety problem. Its casual use as a method for avoiding ground loops
in analog
audio and video signals (to eliminate hums and buzzes
) is dangerous. Bill Whitlock, president of Jensen Transformers, writes, "never, ever use devices such as 3 to 2-prong AC plug adapters, a.k.a. 'ground lifters', to solve a noise problem!" Whitlock relates how an electrical fault in one device that is connected to its electricity source through an ungrounded cheater plug will result in dangerous, high current flowing through audio or video cables. Whitlock notes that in 1997, consumer audio and video equipment electrocuted nine people.
The cheater plug is also recognized as a safety hazard in laboratory
settings. For example, in August 2005, Tarun Mal, an associate professor at Cleveland State University
, was electrocuted when he plugged a defective fluorescent lamp
into a time switch
using a cheater plug. Subsequently, the state of Ohio
issued seven citations to the university for unsafe electrical conditions. The Scientist notes that four of the University's seven environmental safety experts agreed that use of the cheater plug "is not uncommon in US university labs". Jim Kaufman, CEO of the Laboratory Safety Institute
, says, "When you inspect labs, it's not unusual to find anywhere from one to seven that way."
Removing the grounding pin of the appliance's plug is unsafe, and leaves the appliance without proper grounding even when relocated and plugged into a properly grounded three-prong receptacle.
Replacing the receptacle with the three-prong type and leaving the ground screw unconnected is just as unsafe as using a cheater plug, but has the additional disadvantage that subsequent users of the outlet may not be aware that it is not properly grounded. However, if the ground screw of the receptacle is connected to the neutral
side, electric shock is possible even if the appliance is properly functioning. This is called a "false" or "bootleg" ground
and is a serious safety hazard often undetected by common receptacle tester
s.
Replacing the receptacle with a GFCI receptacle is the safest alternative. If a GFCI receptacle is properly functioning, then it will shut off the power to a faulty appliance to prevent electric shock
. As a safe option that protects all appliances plugged into that receptacle, the National Electrical Code permits such replacement if the installer marks the GFCI as having "No Equipment Ground".
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
-type plug (three prongs) to connect to a NEMA 1-15R non-grounding receptacle (two slots). The use of such an adapter avoids the need to replace receptacles, but is potentially hazardous, if the grounding tab is not actually connected to electrical ground. An alternative identified in the U.S. and Canadian electrical codes is to replace the outlet with a GFCI breaker outlet.
Cheater plugs were previously available with a short flexible grounding wire rather than a screw tab. This allows use of the second duplex outlet that does not have a faceplate screw in the correct location for the screw tab. The grounding wire would be wrapped around the adapter to reach the faceplate screw. However, this ground-wire style of cheater plug was discontinued when it was noted that a loose unattached grounding wire could by accident become inserted into the "hot" blade socket of a nearby outlet, potentially leading to electrocution.
Cheater plugs are also used to break ground loops
Ground loop (electricity)
In an electrical system, a ground loop usually refers to a current, almost always unwanted, in a conductor connecting two points that are supposed to be at the same potential, often ground, but are actually at different potentials. Ground loops created by improperly designed or improperly installed...
in audio systems. This practice has been condemned as disregarding electrical safety. An alternative is to use an isolation transformer
Isolation transformer
An isolation transformer is a transformer used to transfer electrical power from a source of alternating current power to some equipment or device while isolating the powered device from the power source, usually for safety...
made specifically for this purpose.
Use in residences
Three-prong plugs do not fit into the older, two-prong receptacles. When used as intended, the ground pin of the 3-wire receptacle is to be connected to the grounded cover screw, or to an external ground. In 1969 Underwriters LaboratoriesUnderwriters Laboratories
Underwriters Laboratories Inc. is an independent product safety certification organization. Established in 1894, the company has its headquarters in Northbrook, Illinois. UL develops standards and test procedures for products, materials, components, assemblies, tools and equipment, chiefly dealing...
mandated three-prong plugs on small appliance
Small appliance
Small appliance refers to a class of home appliances that are portable or semi-portable or which are used on tabletops, countertops, or other platforms in the United States of America...
s for safety. At that time, only half of the receptacles in U.S. homes were three-prong. Wiring in most homes did not include a grounding wire. The screws and outlet boxes were either connected to the neutral, or connected to nothing. Only in rare jurisdictions where non-metallic cable was prohibited, and armored cable required, do cheater plugs work as intended. In 1971 the U.S. National Electrical Code (NEC) required grounded receptacles in all locations of the home (effective January 1, 1974).
Safety
In the professional audioProfessional audio
Professional audio, also 'pro audio', refers to both an activity and a type of audio equipment. Typically it encompasses the production or reproduction of sound for an audience, by individuals who do such work as an occupation like live event support, using sound reinforcement systems designed for...
and video fields, the cheater plug has been identified as a serious safety problem. Its casual use as a method for avoiding ground loops
Ground loop (electricity)
In an electrical system, a ground loop usually refers to a current, almost always unwanted, in a conductor connecting two points that are supposed to be at the same potential, often ground, but are actually at different potentials. Ground loops created by improperly designed or improperly installed...
in analog
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
audio and video signals (to eliminate hums and buzzes
Mains hum
Mains hum, electric hum, or power line hum is an audible oscillation of alternating current at the frequency of the mains electricity, which is usually 50 Hz or 60 Hz, depending on the local power line frequency...
) is dangerous. Bill Whitlock, president of Jensen Transformers, writes, "never, ever use devices such as 3 to 2-prong AC plug adapters, a.k.a. 'ground lifters', to solve a noise problem!" Whitlock relates how an electrical fault in one device that is connected to its electricity source through an ungrounded cheater plug will result in dangerous, high current flowing through audio or video cables. Whitlock notes that in 1997, consumer audio and video equipment electrocuted nine people.
The cheater plug is also recognized as a safety hazard in laboratory
Laboratory
A laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...
settings. For example, in August 2005, Tarun Mal, an associate professor at Cleveland State University
Cleveland State University
Cleveland State University is a public university located in downtown Cleveland, Ohio. It was established in 1964 when the state of Ohio assumed control of Fenn College, and it absorbed the Cleveland-Marshall College of Law in 1969...
, was electrocuted when he plugged a defective fluorescent lamp
Fluorescent lamp
A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...
into a time switch
Time switch
A time switch is a timer that plugs into an electric socket, between the socket itself and a power plug. This physical arrangement allows the connected device to automatically receive power for a desired duration of time...
using a cheater plug. Subsequently, the state of Ohio
Ohio
Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...
issued seven citations to the university for unsafe electrical conditions. The Scientist notes that four of the University's seven environmental safety experts agreed that use of the cheater plug "is not uncommon in US university labs". Jim Kaufman, CEO of the Laboratory Safety Institute
Laboratory Safety Institute
The Laboratory Safety Institute is a 5013 non-profit organization based in the United States that supports safety in science education.Founded in 1978 by Dr...
, says, "When you inspect labs, it's not unusual to find anywhere from one to seven that way."
Alternatives
There are several alternatives for connecting newer appliances to two-prong receptacles without rewiring the building: removing the grounding pin of the plug, replacing the receptacle with a three-prong outlet, or replacing the receptacle with a GFCI; only the last (GFCI) is safe.Removing the grounding pin of the appliance's plug is unsafe, and leaves the appliance without proper grounding even when relocated and plugged into a properly grounded three-prong receptacle.
Replacing the receptacle with the three-prong type and leaving the ground screw unconnected is just as unsafe as using a cheater plug, but has the additional disadvantage that subsequent users of the outlet may not be aware that it is not properly grounded. However, if the ground screw of the receptacle is connected to the neutral
Ground and neutral
Since the neutral point of an electrical supply system is often connected to earth ground, ground and neutral are closely related. Under certain conditions, a conductor used to connect to a system neutral is also used for grounding of equipment and structures...
side, electric shock is possible even if the appliance is properly functioning. This is called a "false" or "bootleg" ground
Bootleg ground
In mining, "bootleg ground" may refer to overburden that contains undetonated explosives.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...
and is a serious safety hazard often undetected by common receptacle tester
Receptacle tester
A receptacle tester or outlet tester is a device used to verify that an AC wall outlet is wired properly. The tester itself is small device which looks like the "plug in" end of a power cord, with several lights on it rather than an attached cord...
s.
Replacing the receptacle with a GFCI receptacle is the safest alternative. If a GFCI receptacle is properly functioning, then it will shut off the power to a faulty appliance to prevent electric shock
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
. As a safe option that protects all appliances plugged into that receptacle, the National Electrical Code permits such replacement if the installer marks the GFCI as having "No Equipment Ground".