NO, someone is reading the Code backwards.
NO, someone is reading the Code backwards.
I'm doing a "grounding and bonding" continuing education online class and this is one of the questions. It is claiming that a ground screw is not needed in a metal box if you remove one or more of the fiber retention washers and the metal yoke of the receptacle is in direct contact of the metal box. Is this true or am I interpreting this wrong?
and skipping explicit text.
250.146 Connecting Receptacle Grounding Terminal to Box.
....
(A) Surface-Mounted Box. Where the box is mounted on the surface, direct metal-to-metal contact between the device yoke and the box or a contact yoke or device that complies with 250.146(B) shall be permitted to ground the
receptacle to the box. At least one of the insulating washers shall be removed from receptacles that do not have a contact yoke or device that complies with 250.146(B) to ensure direct metal-to-metal contact. This provision shall not apply to cover-mounted receptacles unless the box and cover combination are listed as providing satisfactory ground continuity between the box and the receptacle. A listed exposed work cover shall be permitted to be the grounding and bonding means when (1) the device is attached to the cover with at least two fasteners that are permanent (such as a rivet) or have a thread locking or screw or nut locking means and (2) when the cover mounting holes are located on a flat non-raised portion of the cover.
>>>bonding receptacle TO the box, not the box to the receptacle.
(B) Contact Devices or Yokes. Contact devices or yokes designed and listed as self-grounding shall be permitted in conjunction with the supporting screws to establish equipment bonding between the device yoke and flush-type boxes.
>>>This may be leading people astray.
250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes.
....
(B) Grounding Continuity. The arrangement of grounding connections shall be such that the disconnection or the
removal of a receptacle, luminaire, or other device fed from the box does not interfere with or
interrupt the grounding continuity.
>>> you remove the grounded receptacle and you remove the grounding of the box!
(C) Metal Boxes. A connection shall be made between the one or more
equipment grounding conductors and a metal box by means of a grounding screw that shall be used for no other purpose, equipment listed for grounding, or a listed grounding device.
>>> the EGC must be connected to the box