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Ground rod installation for shed building required or not?

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    #16
    Originally posted by hbiss View Post
    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 ?
    Before 1984 (that book was handy, it requires the second). I'd wildly guess in the '50s or '60s, but that's before my time.

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      #17
      Originally posted by PaulMmn View Post
      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)?
      Sure even a 10' rod could be used if you only wanted to pound in 8' and leave the rest sticking out of the ground. Good luck convincing the inspector that it's a 10 rod.
      Rob

      Moderator

      All responses based on the 2014 NEC unless otherwise noted

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        #18
        Something tells me that it was written that the ground rod should be driven to below grade if not to a point below frost line (if you have that). Reason I say this is because I have noticed some rods above grade tend to be pulled up every season due to the freeze, albeit in small amounts but after 10 years all of a sudden you find 2’ sticking out of the ground.

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          #19
          Originally posted by mopowr steve View Post
          Something tells me that it was written that the ground rod should be driven to below grade if not to a point below frost line (if you have that). Reason I say this is because I have noticed some rods above grade tend to be pulled up every season due to the freeze, albeit in small amounts but after 10 years all of a sudden you find 2’ sticking out of the ground.
          If an 8 foot rod doesn't get you below frost line - it's too darn cold.
          I live for today, I'm just a day behind.

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            #20
            Originally posted by hbiss View Post
            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
            Mentioning of 25 ohms and additional electrodes if over 25 ohms goes back a long way AFAIK. Oldest code book I have is 1987 and that is mentioned in there.

            What did change somewhat more recently is in 2011 they rewrote things.
            Before 2011 it always said something to the effect that if it didn't have a resistance of 25 ohms or less you needed to provide an additional electrode. 2011 and after it says you must have an additional electrode, but then they added an exception that says if a single electrode has resistance of 25 ohms or less the additional electrode is not required.

            This ultimately eliminated having someone say "I'm not certain if my rod is 25 ohms or less" and not driving a second rod. Now with the wording like it is, you must use a second electrode unless you prove the first is 25 ohms or less.

            I know most everyone around these parts only drove one rod never measured the resistance and moved on until that change in 2011. Now it is simpler and even less expensive to just drive two rods than to mess with proving the first one is low enough resistance.
            I live for today, I'm just a day behind.

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              #21
              Originally posted by kwired View Post
              Now it is simpler and even less expensive to just drive two rods than to mess with proving the first one is low enough resistance.
              And the trench is the perfect place to drive them.
              Master Electrician
              Electrical Contractor
              Richmond, VA

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                #22
                Originally posted by kwired View Post
                I know most everyone around these parts only drove one rod never measured the resistance and moved on until that change in 2011. Now it is simpler and even less expensive to just drive two rods than to mess with proving the first one is low enough resistance.
                I think that's what happened here also. I don't think we (in NY) even adopted the 2011, went straight from 2008 to 2014 but I know I started using 2 rods before the 2008 but I don't know when.

                The house I'm in now was built in 1955 and didn't even have a ground rod for it's original 100A service. Only bonded to the water line. So somewhere after 1955 (and whatever code we were on then, probably from the 40's) a ground rod became required.

                Before my time.

                -Hal

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                  #23
                  Originally posted by kwired View Post
                  If an 8 foot rod doesn't get you below frost line - it's too darn cold.
                  No, what I’m saying is that when the top few inches to a foot of soil freezes it heaves and pulls up on the rod. As the rest of the rod is still in damp soil and slowly gets pulled out.

                  Just something I have noticed after many years after even myself driving rods that I originally had maybe a couple inches above grade and now are a foot out of the ground.

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                    #24
                    The reason that all separate buildings require a grounding electrode system is to prevent damage/fires from a lighting strike. Lighting does not care if its a 30 amp feeder or 3000 amp feeder. For a branch or multwire branch circuit, no GES is required as there is less electrical and equipment.
                    The GES takes care of the grounding but still need bonding, IE a 4th wire back to the source. Many in my classes and myself thought is you ran a 4 wire feeder you didn't need a GES. Nope. Still need the GES.
                    Orginally we would run a 3 wire feeder, GES and use the white wire for both neutral and a EGC. That hasn't been allowed since 2002
                    Moderator-Washington State
                    Ancora Imparo

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                      #25
                      Originally posted by tom baker View Post
                      The reason that all separate buildings require a grounding electrode system is to prevent damage/fires from a lighting strike.
                      I don't fully agree with that. It gives a reference to ground that can give lightning a more preferred path, there is still no assurance it will prevent damage.
                      I live for today, I'm just a day behind.

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                        #26
                        Originally posted by kwired View Post
                        I don't fully agree with that. It gives a reference to ground that can give lightning a more preferred path, there is still no assurance it will prevent damage.
                        My reply should of been reduce damage from fires and overvoltage, same reasons as in 250.4
                        Moderator-Washington State
                        Ancora Imparo

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