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I have an 8 foot ground that hits solid rock at 4 feet. How can I meet the safety requirements for the 8 foot into the ground rule? Can it be cut in half and have two 4 foot rods driven into the ground?

  • 1
    Talk to your local authority. 8' is a national rule, local jurisdictions are meant to tune it for local conditions, they've seen the problem before and will have an answer. – Harper Jun 24 '17 at 14:15
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    Have you considered another type of electrode? – ThreePhaseEel Jun 24 '17 at 14:24
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You can drive at an angle. If I remember correctly, you can dig a trench and lay the 8 foot rod(s) flat in the bottom of it (Personally, I'd never go with one rod anyway.) If you wanted a really good ground, you simply excavate your foundation to bedrock and use an UFER ground in the foundation concrete (it's a concrete encased ground electrode formed by electrically connecting the reinforcing steel in your concrete foundation - or a section of copper cable, but the steel is there and serves multiple purposes.) 20 foot minimum, but common sense is to tie all the steel together for the best possible result.

Note on re-reading - A CCE/Ufer ground does not require excavating to bedrock, but if bedrock is 4 feet down, you might was well put your foundation on the bedrock...

Responding to erroneous comment below:

Exception 1 to 250.68 indicates that buried electrode connections and concrete-­encased connections to electrodes shall not be required to be accessible. Exception 2 indicates that exothermic welded connections and irreversible connections to grounding electrodes that are encapsulated in fireproofing material are not required to be accessible. The exception applies not only to the connection but also the mechanical fastening means, such as a nut or bolt, that establishes the connection to the metal framing member.

From EC Mag article. But you can also look it up in the code, that was just faster to find.

  • FYI - The first 2 feet of a ground rod are considered to be ineffective due to the variation of moisture in topsoil. That's why the code requires a minimum of a 6' rod. The deeper the rod the better the ground. Also the code requires all mechanical connections to the grounding electrode to be accessible for maintenance. Also in this state if a ground rod is used as the only means of grounding in a dwelling unit. It requires a least two be used, driven a minimum of 6' apart. – Retired Master Electrician Jun 24 '17 at 15:45
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I'm having the same problem. My plan is to rent a roto-hammer (big one) with a grounded rod driver attachment, apparently this is a common problem. If what I've seen on Youtube is real, this tool will pound it through anything with ease. Alternatively, you get a well driller to sink you two 10-12 foot holes, and then grout your rods in. I'd leave the laying them horizontal as the last resort, some AHJ's might ask "So what's the phone # of the guy you asked to drill this for you".

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    Drilling a rod into bedrock may not get you the results you want, even with two widely spaced rods. I'd be much more hip to a concrete-encased electrode, myself. – ThreePhaseEel Jun 25 '17 at 22:01
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Try calling your local electrical supply and see if they have advanced driven rods. These are grounding rods with carbide tips to be driven in with a hammer drill, just like drilling for oil☺. Or you could use grounding plates that are buried 2x2 plates of copper. Oh and personally I have a ground rod at each corner of the house all tied into the electrical supply.

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