Grounded receptacles require proper wiring methods and proper implementation of those methods, including compression wire nuts that chemically bond wires to each other, rather than wires just twisted together.
Electrical continuity for power wiring in buildings requires bonding conductors wherever continuity relies on more than one piece of conductor (wire). Bonding involves a chemical bond between separate pieces of conductor that will carry current.
In this photo, the installer has used a common shortcut that may provide adequate grounding immediately upon completion of the job, but which will degrade over time, due to oxidation of the outer surface of the copper equipment grounding conductors. For copper EGC’s, oxidation only occurs on the outer surface of the copper. By creating a proper bond at the time of installation, oxidation cannot penetrate and interrupt the bond over time.
For a receptacle mounted in a plastic (insulating) wire box such as the one in the photo, the equipment grounding conductors (EGC’s) must be properly bonded to each other and to the receptacle yoke. (On a metal wire box, grounding for the receptacle may be via the conductive box itself, in some cases). In the photo, the installer has bonded one EGC properly to the receptacle’s ground terminal, but the other EGC has been lazily wrapped around the one leading to the receptacle’s grounding terminal. This particular installation is lazy twice over, since the wrap is haphazard to the extent the two conductors could conceivably lose contact with one another, regardless of oxidation. Secondly, these EDC’s should have been bonded together using a wire nut, which would compress them to one another and cut fresh, un-oxidized points of contact for chemical bonding of the metal conductors (including the metal in the wire nut) when they are compressed together. The installer could have used a third copper conductor in a standard wire nut, or a ‘greenie’ type wire nut that permits the receptacle’s wire end to pass through the wire nut, or by wrapping one EGC on the receptacle terminal with a ‘tail’ left over to bond to the remaining EGC.
Each of the possible proper methods requires only slightly more time and material. View the following video for an example of proper grounding and conductor connections in a receptacle enclosure.
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