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Ground rod installation for shed building required or not?

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    Ground rod installation for shed building required or not?

    Sunday funday. So to my understanding in a residential setting it is required to install a ground rod for a new sub panel install at the shed building where the panel will be installed. Am I correct?

    Here's what I would do.
    1) PVC underground dig trench dig it deep enough by referencing burial depth chart.

    2) pull in 4 wires to match 50 amp load of new sub panel...(2 hots,neutral, and ecg)from main panel of home to subpanel at shed.

    3)drive ground rod in ground 8 feet down til just above grade.

    4) don't bond mbj at subpanel. It's already bonded at main panel.

    5) run and connect ground from sub panel to ground rod at shed.

    6) terminate 4 conductors from main panel to subpanel.(2hot,neutral and egc.)

    7) distance is roughly 100 feet away from house to shed.

    Let me know what you think. Happy Sunday to all.






    Sent from my Moto Z (2) using Tapatalk

    #2
    Sounds fine but you'll need two ground rods or prove that one is 25 Ω or less and the rod(s) need to at or below grade to the top.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

    Comment


      #3
      Originally posted by Danny89 View Post
      So to my understanding in a residential setting it is required to install a ground rod for a new sub panel install at the shed building where the panel will be installed. Am I correct?
      That's pretty much true for any structure that's fed by more than a branch circuit (residential or not, see 250.32). Otherwise, that all looks OK.

      Comment


        #4
        Originally posted by infinity View Post
        Sounds fine but you'll need two ground rods or prove that one is 25 Ω or less and the rod(s) need to at or below grade to the top.
        Interestingly, I've never been required to provide more than a single rod for a detached building.
        Master Electrician
        Electrical Contractor
        Richmond, VA

        Comment


          #5
          Originally posted by LarryFine View Post
          Interestingly, I've never been required to provide more than a single rod for a detached building.
          You're not required to install any rods but you are required to connect to a GES or a single electrode is none are present. A single rod needs to be 25 Ω or less to qualify as an electrode or two rods.
          Rob

          Moderator

          All responses based on the 2014 NEC unless otherwise noted

          Comment


            #6
            Awesome thanks guys!

            Sent from my Moto Z (2) using Tapatalk

            Comment


              #7
              Common grounding electrode

              Originally posted by infinity View Post
              You're not required to install any rods but you are required to connect to a GES or a single electrode is none are present. A single rod needs to be 25 Ω or less to qualify as an electrode or two rods.
              So, would it be permissible to run the GEC back to the house and tap the existing Grounding Electrode System?

              Comment


                #8
                Originally posted by Greg1707 View Post
                So, would it be permissible to run the GEC back to the house and tap the existing Grounding Electrode System?
                Essentially, you do, but it's an ECG from the house to the shed.

                Possibly oversimplifying the whole thing (and some exceptions apply)--

                every structure must have it's own GES, which is composed of grounding electrodes (rod or rods, ufer, plate, etc) and a GEC connecting them (house is a structure, shed is another structure, etc).

                if the structure is fed by a feeder (not a service), that feeder must contain a ECG (more exceptions, not relevant to most new installations).

                the structure's GES must connect to the ECG in the feeder.

                In the end, run a 4-wire feeder from the house, pound two rods at the shed, connect the rods to the grounding conductor from the house and to the ground bar in the subpanel. Profit .

                I'm sure there's a Mike Holt graphic of all this.

                Comment


                  #9
                  shared GES

                  Can both structures share the same GES? For example, if the ground rods for the house are close by is there a need to install additional rods or can the nearby house rods be used?

                  Comment


                    #10
                    They can be shared and, if close enough, should be.
                    Master Electrician
                    Electrical Contractor
                    Richmond, VA

                    Comment


                      #11
                      Originally posted by LarryFine View Post
                      They can be shared and, if close enough, should be.
                      Well I am inclined to agree but I don't know that the code actually says that.
                      Bob

                      Comment


                        #12
                        Originally posted by petersonra View Post
                        Well I am inclined to agree but I don't know that the code actually says that.
                        I agree the wording is a bit ambiguous because it does not say that a separate GES or electrode is required for each structure.

                        250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).
                        (A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with Part III of Article 250. The grounding electrode conductor(s) shall be connected in accordance with 250.32(B) or (C). Where there is no existing grounding electrode, the grounding electrode(s) required in 250.50 shall be installed.
                        Rob

                        Moderator

                        All responses based on the 2014 NEC unless otherwise noted

                        Comment


                          #13
                          Originally posted by petersonra View Post
                          Well I am inclined to agree but I don't know that the code actually says that.
                          I based my statement on the "if available must be connected" and "all electrodes bonded together" rules.
                          Master Electrician
                          Electrical Contractor
                          Richmond, VA

                          Comment


                            #14
                            Originally posted by infinity View Post
                            Sounds fine but you'll need two ground rods or prove that one is 25 Ω or less and the rod(s) need to at or below grade to the top.
                            All the way to the top? Or would a 9' ground rod with a couple of inches showing meet the requirements (ie with a clamped on ground wire back to the box)?

                            Comment


                              #15
                              Originally posted by LarryFine
                              Interestingly, I've never been required to provide more than a single rod for a detached building.

                              Originally posted by infinity
                              You're not required to install any rods but you are required to connect to a GES or a single electrode is none are present. A single rod needs to be 25 Ω or less to qualify as an electrode or two rods.
                              I agree with Larry. Does anybody know what year the Code was changed to allow two ground rods if a single is more than 25Ω ?

                              -Hal

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