![]() In this application, the faceplate of the GFCI receptacle must be marked, “No Equipment Ground”, and the face plate of each subsequent three-prong receptacle must be marked, “GFCI Protected, No Equipment Ground”. Again, bear in mind, this option does not provide an equipment ground and still poses a potential shock hazard. The third option is to install a GFCI receptacle in the first position in the branch circuit, or alternatively a GFCI circuit breaker, with all remaining downstream outlets replaced with standard three-prong receptacles. If the GFCI circuit fails, or an illegal bootleg ground has been wired within the electrical branch circuit, a potential shock hazard still exists. Most often, current bleed occurs when there is an electrical connection between normally current carrying conductors of the branch circuit and chassis of the receptacle, or connected appliance. Any measured difference in excess of 5 mA will trip the GFCI receptacle rendering the outlet and connected appliance safe to touch. The ground-fault circuit interrupter monitors amperage flowing out on the ungrounded “hot” conductor and compares to the return amps on the grounded “neutral conductor. In this application, the GFCI receptacle or faceplate must be marked, “No Equipment Ground” to alert a potential user that any connected equipment will not be grounded during use. Although this type of installation is safer, this option still does not provide a dedicated ground-fault path back to the main electrical panel. The second option is to replace each ungrounded receptacle with a ground-fault circuit interrupter (GFCI) receptacle. Third, without remedy of the first two, the homeowner or occupants are left with a potential shock hazard or worse yet lethal electrocution risk. Second, this option provides no dedicated EGC or ground-fault path, for safety. First, this option does not change the receptacle’s configuration to the ubiquitous three prong configuration required by nearly all modern appliances and electrical devices. For most homeowners this is the least attractive option for a few reasons. The first option allows existing two-prong receptacles to be replaced with new two-prong receptacles. The National Electric Code (NEC) section 406.4(D)(2) provides three replacement options for existing two-prong receptacles that do not have a connection to an EGC. What Options Do I Have to Replace Existing Two Prong Outlets? Homes built prior to 1962 may have neither. Finally, in 1962, the NEC was revised to require all new electrical branch circuits include an equipment grounding conductor and use of three-prong receptacles. In 1956, the NEC began requiring the addition of an equipment grounding conductor with new electrical wiring and further expanded the use of grounded receptacles to basements, garages, and outdoors. ![]() The first introduction of three-prong receptacles occurred in 1947 but was limited only to laundry rooms. The primary replacement has been non-metallic (NM) two wire cable with a dedicated equipment ground. Beginning in the 1930s new wiring methods were developed, which eventually supplanted new knob and tube installations inside homes. Old two-wire knob and tube circuits were installed in the United States from the 1880s through the 1950s. This is why two-prong receptacles are dangerous. Repeated fault cycles will degrade the wire insulation which can eventually lead to arcing or a structure fire. Additionally, without the presence of an equipment grounding conductor, high ampere fault conditions are carried back to the main electrical panel via the neutral conductor. By tripping the circuit breaker, power is switched off in the circuit, rendering the faulted device safe to touch.īecause two-prong receptacles do not offer any such ground-fault protection, occupants may be exposed to shock or electrocution hazards. In the event a connected appliance, electrical fixture or three-prong receptacle itself were to develop a ground-fault condition, current is directed along the EGC back to the circuit breaker forcing the breaker to trip. The equipment grounding conductor provides three-prong receptacles a low resistance fault path back to the main electrical circuit breaker panel. The purpose of the EGC is to serve as a safety system, specifically to protect people from electric shock or lethal electrocution. An equipment grounding conductor can be identified as the bare copper wire or green sheathed conductor bundled together with the black ungrounded “hot” conductor, and the white grounded “neutral” conductor. Two-prong receptacles by their design are ungrounded, and therefore do not have a connection to an equipment grounding conductor (EGC). Fire Administration, 12 percent of residential homes fires in the United States involve outlet receptacles. They are a well-known cause of residential home fires worldwide. Two prong outlets are inherently unsafe and can be extremely dangerous.
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