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    Bonding Devices to Junction Boxes

    I am installing a raceway system that uses EMT and metal junction boxes. My question is when installing devices in particular 15A 120V receptacles and switches are these required to be bonded to the junction box if the EGC in this installation is the EMT raceway? Does the NEC accept the 6-32 device mounting screws as an effective means for bonding these devices to the EMT raceway system?

    #2
    250.118 accepts EMT as a EGC, grounding type receptacles need no bonding jumper with a properly bonded metal box

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      #3
      See 250.146. If the boxes are in a wall, the screws on the receptacle are not acceptable as the required bonding. If you don't want to install a physical jumper, you can use "self-grounding" receptacles. Self grounding receptacles have a spring clip on one end of the yoke that improves the bonding connection and permits you to omit a wire type bonding jumper.
      Don, Illinois
      (All code citations are 2017 unless otherwise noted)

      Comment


        #4
        Originally posted by don_resqcapt19 View Post
        See 250.146. If the boxes are in a wall, the screws on the receptacle are not acceptable as the required bonding. If you don't want to install a physical jumper, you can use "self-grounding" receptacles. Self grounding receptacles have a spring clip on one end of the yoke that improves the bonding connection and permits you to omit a wire type bonding jumper.

        Forgot "self" a normal receptacle isn't the same as stated above.

        Comment


          #5
          Originally posted by mjc1060 View Post
          I am installing a raceway system that uses EMT and metal junction boxes.
          It sounds like you are installing a flush mounted system where the pipe and boxes are recessed in the walls. However, if the system is surface mounted, there are more Code passages.

          Break is down into the parts.

          The EMT is the EGC and is bonded to the metal junction box by the EMT connector.

          In a surface mounted the box, many times the next piece is a raised cover or a plaster ring, which needs to be bonded to the box. A plaster ring is bonded by the two box 8/32 screws holding the flats of the plaster ring tight to the box.

          A raised cover, if it has flats for the box 8/32 screws like a plaster ring, also is bonded by those 8/32s. However, legacy raised covers that require a approx. 3/4" long cover screw are not bonded by the 8/32 screws.

          Next, the device mounts to the cover or plaster ring. When held with two screws, the device is generally bonded to the cover or plaster ring. An interesting note: be sure to remove one of the 6/32 screw retaining fiber (or plastic) washers from between the yoke and the surface mounted box or plaster ring to effectively bond the device yoke to the metal box or ring. (Removal of the retaining washer does NOT help with flush mounted boxes and plaster rings.)
          Another Al in Minnesota

          Comment


            #6
            10 boxes, or 1,000 boxes ??

            http://www.homedepot.com/p/Ideal-12-...392R/202894316

            or if the box used has no egc screw hole(s) then use a egc bonding type of locknut/washer on the conduit, pigtail from there.

            a few extra $$ for the added safety (not relying on mounting screws) imho is well worth it.
            Last edited by FionaZuppa; 07-20-16, 11:45 AM.

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              #7
              Bonding devices to EMT raceways with separate EGC conductors

              The installation I am referring to is one in which the EMT raceway is concealed behind drywall. Thank you for the interpretation. I prefer to use a separate EGC conductor. This brings another question. Does the NEC require the EGC to be bonded to the junction box with a 10-32 grounding screw that is listed for this application? If this is not done and the EGC is terminated on only the devices and the panel board am I creating a parallel grounding path for potential fault current?

              Comment


                #8
                Originally posted by mjc1060 View Post
                The installation I am referring to is one in which the EMT raceway is concealed behind drywall. Thank you for the interpretation. I prefer to use a separate EGC conductor. This brings another question. Does the NEC require the EGC to be bonded to the junction box with a 10-32 grounding screw that is listed for this application? If this is not done and the EGC is terminated on only the devices and the panel board am I creating a parallel grounding path for potential fault current?
                If you run a wire type EGC or use the raceway is up to you. It is worth pointing out that the impedance of the raceway will be lower than the impedance of any wire EGC you will put inside it.

                If you choose to run a wire type EGC 250.148 requires you connect it to the box.

                The screw does not have to be listed or even green, it does have to comply with 250.8

                As far as parallel paths for fault current that is a good thing.

                Comment


                  #9
                  Originally posted by FionaZuppa View Post
                  I was expecting that link to take us to grounding rods.

                  Comment


                    #10
                    Originally posted by iwire View Post
                    I was expecting that link to take us to grounding rods.
                    I thought it would be earth rods.
                    The more they overthink the plumbing, the easier it is to stop up the drain

                    Comment


                      #11
                      Originally posted by dkidd View Post
                      I thought it would be earth rods.
                      I refuse to call them that until the NEC does.

                      Comment


                        #12
                        Originally posted by iwire View Post
                        The screw does not have to be listed or even green, it does have to comply with 250.8
                        This is one of the more interesting anomalies in the materials we use in this trade. 250.8(5) does not call for "listed" machine screws, nor does it specify 10/32. However, the machine screw must engage at least two threads, or be secured with a nut.

                        If you go to the manufacturer's published literature for a "ground screw", it is extremely rare to find one that is actually tested and listed by a nationally recognized testing laboratory. Try it.

                        Originally posted by mjc1060 View Post
                        . . . am I creating a parallel grounding path for potential fault current?
                        As Iwire states, EGCs are required to be connected together, again and again. The effect, when there are multiple circuits in multiple raceways, when applying 250.144, 250.148, and especially 250.148(C), is to create a mesh, or "net", of EGC paths back to the "source" resulting in an effective fault clearing path that is harder to disrupt.
                        Another Al in Minnesota

                        Comment


                          #13
                          Originally posted by iwire View Post
                          I was expecting that link to take us to grounding rods.
                          not a bad idea
                          put one every 10ft along the horizontal length of the run, then bond up to the box

                          Comment


                            #14
                            Originally posted by FionaZuppa View Post
                            not a bad idea
                            put one every 10ft along the horizontal length of the run, then bond up to the box






                            I am happy you received that in the spirit it was given. Just joking around.

                            Comment

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