Q. What is the requirement for attaching the equipment grounding conductor to metal boxes?
A. If circuit conductors are spliced or terminated on equipment within a metal box, the equipment grounding conductor associated with those circuits must be connected to the box in accordance with the following [250.148]: (see Figure)
Exception: The circuit equipment grounding conductor for an isolated ground receptacle installed in accordance with 250.146(D) isn't required to terminate to a metal box.
· Equipment grounding conductors must be spliced together with a device listed for the purpose [110.14(B) and 250.148(A)]. Note: Wire connectors of any color can be used with equipment grounding conductor splices, but green wire connectors can only be used with equipment grounding conductors.
· Equipment grounding conductors must terminate in a manner such that the disconnection or the removal of a receptacle, luminaire, or other device won't interrupt the grounding continuity [250.148(B)].
· Equipment grounding conductors within metal boxes must be connected to the metal box with a grounding screw that's not used for any other purpose, an equipment fitting listed for grounding, or a listed grounding device such as a ground clip [250.148(C)].
· Equipment grounding conductors aren't permitted to terminate to a screw that secures a plaster ring.