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MC cable & grounding. Tail to the box & receptacles?

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    MC cable & grounding. Tail to the box & receptacles?

    12/2 MC cable in a 5" box.
    You take the green wire & secure it to the box with a green ground screw. Thus grounding the box.

    Do you also need to bring a tail to the ground screw of a duplex receptacle?

    If yes, why? If the box is grounded, then so is the receptacle through the 6/32 screws. Or alternately, if the receptacle is grounded, then the box is grounded through the 6/32's.

    I'm feeding a 5" box for quad receptacles plus 2 12/2 jumpers to other boxes. I end up with 6 grounds under a wire nut.

    #2
    The 6-32 screws alone are not permitted to ground the receptacle. The device would need a bonding jumper or must be a self grounding receptacle. Also you cannot connect the EGC to the device and ground the metallic box through the device.
    Rob

    Moderator

    All responses based on the 2017 NEC unless otherwise noted

    Comment


      #3
      Originally posted by infinity View Post
      The 6-32 screws alone are not permitted to ground the receptacle. The device would need a bonding jumper or must be a self grounding receptacle. Also you cannot connect the EGC to the device and ground the metallic box through the device.
      If this is a metal box that has the EGC bonded to it, wouldn't a regular receptacle with the plastic washers removed and metal to metal ( yoke to box) be okay?
      "Electricity is really just organized lightning." George Carlin


      Derek

      Comment


        #4
        I meant self-grounding receptacles.

        That's always been good enough with Bx. The jacket of the Bx bonding the box & the 6/32's grounding the receptacle.
        So why not with MC cable?

        I know I'm conflating 'bonding' & 'grounding' but that's a whole other issue with it's own section of the forum.

        Comment


          #5
          Originally posted by jumper View Post
          If this is a metal box that has the EGC bonded to it, wouldn't a regular receptacle with the plastic washers removed and metal to metal ( yoke to box) be okay?

          Not for the box he's using.


          Originally posted by Sir String View Post
          I meant self-grounding receptacles.

          That's always been good enough with Bx. The jacket of the Bx bonding the box & the 6/32's grounding the receptacle.
          So why not with MC cable?

          I know I'm conflating 'bonding' & 'grounding' but that's a whole other issue with it's own section of the forum.

          If the receptacle is self grounding you can use it without a bonding jumper for either AC or MC to a grounded metal box. If it's not self grounding you need a bonding jumper for either of those wiring methods.
          Rob

          Moderator

          All responses based on the 2017 NEC unless otherwise noted

          Comment


            #6
            If you switched to MCap and self grounding receps, you wouldn't have to splice any grounds.

            Comment


              #7
              Originally posted by Cow View Post
              If you switched to MCap and self grounding receps, you wouldn't have to splice any grounds.
              Better get more wire...

              Third sentence in 250.64, + ...shall apply at each end... between cabinet or equipment... continually
              If you are even thirsty, you are two quarts low.

              Comment


                #8
                Originally posted by Sir String View Post
                12/2 MC cable in a 5" box.
                You take the green wire & secure it to the box with a green ground screw. Thus grounding the box.

                Do you also need to bring a tail to the ground screw of a duplex receptacle?

                If yes, why? If the box is grounded, then so is the receptacle through the 6/32 screws. Or alternately, if the receptacle is grounded, then the box is grounded through the 6/32's.

                I'm feeding a 5" box for quad receptacles plus 2 12/2 jumpers to other boxes. I end up with 6 grounds under a wire nut.
                I'd go with406.3(C)
                The EGC contacts of a recept... shall be grounded by connection to the EGC of the circuit supplying the recept.

                The branch circuit wiring method shall include or provide an EGC to which the EGC contact(s) of the recept. are connected

                406.3 D,1 points to that too. But I don't know what you mean by 5" box. Is that a 4 and 11/16" ?
                Fixing shorts for money

                Comment


                  #9
                  Originally posted by jumper View Post
                  If this is a metal box that has the EGC bonded to it, wouldn't a regular receptacle with the plastic washers removed and metal to metal ( yoke to box) be okay?
                  Why is that the way you have been doing it. You need to use those receps with the brass clip and are considered self grounding. for this purpose.

                  Comment


                    #10
                    Originally posted by Finite10 View Post
                    ...But I don't know what you mean by 5" box. Is that a 4 and 11/16" ?
                    Yes, of course.

                    Comment


                      #11
                      Originally posted by Finite10 View Post
                      I'd go with406.3(C)
                      But I don't know what you mean by 5" box. Is that a 4 and 11/16" ?
                      5" box is slang for a 4 11/16" boxes.


                      Also take a look at 250.146, 250.146(B) and 250.148(B).
                      Rob

                      Moderator

                      All responses based on the 2017 NEC unless otherwise noted

                      Comment


                        #12
                        Originally posted by Sierrasparky View Post
                        Why is that the way you have been doing it. You need to use those receps with the brass clip and are considered self grounding. for this purpose.


                        No, I am a "bondaholic", I use self grounding receptacles and attach a pigtail.
                        "Electricity is really just organized lightning." George Carlin


                        Derek

                        Comment


                          #13
                          Originally posted by infinity View Post
                          5" box is slang for a 4 11/16" boxes.


                          Also take a look at 250.146, 250.146(B) and 250.148(B).
                          250.146 is what I was referring to

                          Say I used MC in the following picture and bonded the box with the EGC, Do I still need self grounding receptacles?

                          "Electricity is really just organized lightning." George Carlin


                          Derek

                          Comment


                            #14
                            If the device yoke is in contact with the box, then that's right.

                            Comment


                              #15
                              Originally posted by George Stolz View Post
                              If the device yoke is in contact with the box, then that's right.
                              I alwas thought you needed those self grounders!

                              Comment

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