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Grounding Rod Connections

December 7, 2005

Q: Am I permitted to connect two ground rods spaced eight feet apart to the service without running the grounding electrode conductor from one rod to the other? What parts of the NEC would allow or not permit such an installation?

A: Yes, you are permitted to run individual grounding electrode conductors from each ground rod to the service grounded conductor terminal in the service disconnecting means. The size of the grounding electrode conductor from each ground rod cannot be smaller than 6 AWG copper.

A single 6 AWG copper conductor is also permitted. It can be run from one rod to the other and then to the service or metal cold water pipe within 5 feet of where the pipe enters the building. The exception to this rule allows the connection to be made beyond 5 feet in commercial and industrial buildings under limited conditions [See 250.52(A)(1)].

If the ground rods are the only grounding electrodes for the service because there is no buried metal water pipe and the building structural steel is not effectively grounded, a single grounding electrode conductor is permitted to run from one rod to the other and then to the grounded service conductor, or two separate grounding electrode conductors (one from each rod) are permitted to be connected to the grounded (neutral) service conductor in the service disconnecting means. The part that allows this is 250.64(F).

Methods that are suitable for connecting grounding electrode conductors to grounding electrodes and grounded circuit conductors are outlined in 250.70.

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Comments

3 Responses to “Grounding Rod Connections”

  1. Scooter on December 11th, 2008 7:45 pm

    Is a ground rod required at the main panel for residential construction?

  2. David Huff on June 27th, 2011 7:22 pm

    I suspect that when lightening hit one of our tallest trees in the yard, the strike went to ground. many years ago I ran 2/0 triplex AL wire underground to an out building. The trench is almost 4 feet deep but i think at least one of the feeder wires took the charge as during the winter months i found out I had low voltage on one wire or leg of the 100 amp 120/240 single phase service to my outbuilding. The one wire has some resistance and does not read to ground, but yet still will only pass low voltage. I suspect it is burned, but not 100 % sure.

    Is there a way to attempt to find the bad spot, perhaps by ringing with a service finder and power applied to the wire?

  3. brian k on October 23rd, 2011 6:22 pm

    I have a two family house with 2 100 amp panels in the basement. I have one grounding rod connected by #4 wire to one of the panels and a #4 wire going from one panel to the other panel. Is this ok or do I have to have 2 seperate wires going to the single rod?

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