250.146 Connecting Receptacle Grounding Terminal to Box
Receptacles must have their grounding contacts connected to an effective ground-fault current path by bonding the receptacle’s grounding terminal to a metal box, unless the receptacle’s grounding terminal is grounded (bonded) to an effective ground-fault current path by one of the methods provided in (A) through (D). See 406.3 for additional details. Figure 250–186
Figure 250–187 The NEC does not restrict the position of the receptacle grounding terminal; it can be up, down, or sideways. All Code proposals to specify the mounting position of receptacles have been rejected.(A) Surface-Mounted Box. Where the box is mounted on the surface, direct metal-to-metal contact between the device yoke and the box can serve as the effective ground-fault current path. To ensure an effective ground-fault current path between the receptacle and metal box, at least one of the insulating retaining washers on the yoke screw must be removed. Figure 250–188
Receptacles secured to a metal cover [406.4(C)] must have the receptacle’s grounding terminal bonded to the box, unless the box and cover are listed as providing continuity between the box and the receptacle. Figure 250–189
(B) Self-Grounding Receptacles. Receptacle yokes designed and listed as self-grounding can be used to establish the effective ground-fault current path between the device yoke and a metal outlet box. Figure 250–190
Outlet boxes cannot be set back more than 1⁄4 in. from the finished mounting surface [314.20].
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