How to Drive and Connect a Pair of Ground Rods

Why this matters

Ground rods are the cheapest part of a service and the part most often redone after an inspection. The rods themselves rarely fail; the details do: a second rod set 4 ft from the first, an acorn clamp with two conductors under a one-conductor listing, a rod that hit rock and got cut off at grade with 5 ft in the ground, a grounding electrode conductor spliced with a split bolt behind the shrubs. Each of those is a red tag, and the last two are invisible once the dirt is back. This card is the install, from the locate call to the clamp, including what to do when the rod will not go down.

How to confirm what electrodes the building already has, and test the system, belongs to the SOP Grounding Electrode System Verification. Sizing the conductor in general is the Grounding Electrode Conductor Sizing Card; this card uses the one row of it that rods need. Citations are NEC 2023 (2020 where the section moved), as adopted, local amendments checked; inspections per the AHJ.

Why two rods instead of a test

250.53(A)(2) requires a single rod electrode to be supplemented by an additional electrode unless the single rod's resistance to earth is 25 ohms or less. You can try to prove the 25 ohms. Doing it honestly takes a fall-of-potential test with probes driven well out from the rod, in soil whose moisture moves the reading from season to season, and a reading taken in a wet April does not describe the same rod in a dry August. Most shops and most inspectors treat the second rod as the default: it takes less time than a valid test and it ends the question.

The second rod is also often required anyway. A metal underground water pipe used as an electrode must itself be supplemented by another electrode under 250.53(D)(2), in substance, and a pair of rods is the common way to meet that and the single-rod rule at once. How to Bond the Water Pipe at the Service covers the pipe side.

What you are installing

          SERVICE EQUIPMENT
                |
                | 6 AWG Cu GEC, one continuous
                | length, stapled to the wall,
                | sleeved where exposed to damage
 grade =========+==================================
                |
      [CLAMP A]-+---- 6 AWG Cu, no splice ----[CLAMP B]
      DB, listed for                          DB, listed
      2 conductors                            for 1
          |                                       |
        ROD 1                                   ROD 2
        8 ft                                    8 ft
          |                                       |
          |<---- at least 6 ft apart, ----------->|
                 here 10 ft

• The rods. Rod electrodes are at least 8 ft long under 250.52(A)(5). Copper-clad steel 5/8 in is the common rod; a rod of smaller diameter must be listed for the purpose and not less than 1/2 in, in substance, per the same section.
• The spacing. 250.53(A)(3) requires rods used together to be not less than 6 ft apart. Six feet is the minimum, not the target: each rod influences the soil around it, and when the two zones overlap, the second rod adds less. Spacing them at least a rod length apart, 8 ft or more, gets more out of the second rod.
• The conductor. 250.66(A): the portion of the grounding electrode conductor that is the sole connection to rod electrodes is not required to be larger than 6 AWG copper. The jumper between the two rods is sized the same way under 250.53(C).
• Continuity. 250.64(C) requires the GEC in one continuous length, without a splice, except by listed irreversible compression connectors or exothermic welding. A split bolt in the run fails.
• The clamps. 250.70: listed for the electrode and conductor materials, for direct burial where they will be buried (marked "DB"), and not more than one conductor under a clamp unless the clamp is listed for more. Running the GEC unbroken down to rod 1 and on to rod 2 puts the conductor under clamp A twice, which many inspectors read as two conductors, so clamp A is listed for two, or rod 1 gets a second clamp.

Steps

1. Call the one-call center before you drive. An 8 ft rod is excavation for practical purposes, and the rod is driven by a tool that will not tell you it just hit a gas service. Your state's one-call law sets the notice period and who must call. The locate marks utility-owned lines only: ask the owner about private lines (a gas line to a grill or pool heater, landscape lighting, irrigation, a feeder to a shed) and mark them yourself. If a rod stops dead at shallow depth where nothing should be, stop and find out what it hit. A gas odor means everyone away and upwind, no engines started, no switches, and the call to 911 and the gas utility made from a distance. A rod that may have struck an electric line is not touched, nor the tool on it; keep everyone clear and call the utility.

2. Lay out the rods. Rod 1 near the service, where the GEC run is short and the conductor will not be in a lawn mower's path. Rod 2 at least 6 ft from rod 1, measured between the rods at every point along their length, away from foundation footings, under no downspout splash block or walkway. Stake both.

3. Drive the rods. A rotary hammer with a ground-rod driver bit sets an 8 ft rod in minutes and keeps you off a ladder; a sledge on a rod taller than you means swinging overhead from a stepladder, which is how this job puts people in the emergency room. Eye and hearing protection, gloves, and steel-toed boots. Drive until the top is flush with or below grade. 250.53(A)(4) in the 2020 and 2023 editions (250.53(G) in 2017) requires at least 8 ft of rod in contact with soil and the upper end flush with or below ground level unless the above-ground end and the clamp are protected.

4. If the rod will not go down. The same section gives two moves when rock stops the rod: drive it at an angle not more than 45 degrees from vertical, or lay it in a trench at least 30 in deep. A rod that stopped short is pulled with a rod puller or a jack and chain, never cut off: a cut rod with 5 ft in the ground and a clamp on top looks identical to a full rod.

5. Run the GEC. 6 AWG solid copper from the service equipment's grounding terminal down the wall to rod 1, then on to rod 2, one length, no splice. 250.64(B) lets 6 AWG copper run along the building surface without a raceway where it is not exposed to physical damage, stapled to the structure. Where it drops past a walkway or a driveway edge, sleeve it; a ferrous metal raceway around a GEC must be bonded at both ends under 250.64(E), so PVC is the simpler sleeve.

6. Clamp. Clean the rod top, set the clamps, and tighten to the torque the clamp's instructions give with a calibrated tool. Clamp A is listed for both conductor passes or there are two clamps on rod 1. Clamp B is direct-burial listed for one.

7. Show it before you bury it. Photograph both rods, both clamps with their markings legible, the tape measure between the rods, and the continuous GEC. Many AHJs want to see the electrode connections before backfill; schedule it that way rather than digging up a clamp for an inspector. Then backfill.

Worked example: two rods, and one of them hits rock

A 200 A service upgrade on a 1950s house in clay over limestone. The house has a metal water service bonded within 5 ft of entry and one old rod with a corroded clamp. The plan: two new rods, the old one abandoned in place.

Layout. Rod 1 at 3 ft from the meter, under the eave. Rod 2 at 10 ft from rod 1, along the foundation and 2 ft out from it. Ten feet is more than the 6 ft minimum and more than the 8 ft rod length.

Rod 1 drove its full 8 ft with the rotary hammer in about four minutes. Top 1 in below grade.

Rod 2 stopped hard at about 5 ft with 3 ft standing above grade. The probe bar a foot to each side stopped at the same depth: flat bedrock, not a single stone. Rod pulled with a jack and chain.

Try the angle? At the maximum 45 degrees from vertical, 8 ft of rod reaches a depth of 8 times 0.707, about 5.7 ft. The rock is at 5 ft, so an angled rod hits it after about 5 divided by 0.707, or 7.1 ft of travel, short of the 8 ft the section requires in soil. Both directions agree: angling cannot work over flat rock at 5 ft.

So the trench. An 8 ft trench, 30 in deep, running away from rod 1 so that its nearest end is 10 ft from rod 1 and its far end 18 ft. The rod is laid flat in the bottom, all 8 ft in soil, clamp B on its near end. Every point of rod 2 is at least 10 ft from rod 1, which clears the 6 ft rule along the whole length.

GEC. 9 ft down the wall from the service to grade, 3 ft over to rod 1, unbroken through clamp A (listed for two), then 10 ft across to the trench and 30 in down it to clamp B. About 24-1/2 ft of 6 AWG copper, no splice. A PVC sleeve where it crosses the edge of the patio.

Before backfill, photos of both clamps (DB marking visible on each, clamp A's two-conductor listing on its tag), the tape across rod 1 to rod 2's near end reading 10 ft, and the trench depth reading 30 in. The inspector looked at the open trench the same afternoon.

How you know it is right

The finish test is physical, done before anything is covered: both clamps tight to their instructions' torque and marked for direct burial, clamp A listed for the conductors under it, the GEC continuous from the service to rod 2 with no splice except a listed irreversible one, stapled and sleeved where exposed, both rod tops flush with or below grade or the trenched rod at its full depth, and the spacing at least 6 ft at every point. Testing the electrode system, if the job or the AHJ calls for it, follows Grounding Electrode System Verification.

What changes the answer

• A concrete-encased electrode exists. If the footing has rebar or a bare conductor meeting 250.52(A)(3), it is part of the system and must be used if present (an existing building's footing that cannot be reached without disturbing the concrete is exempt), and rods supplement rather than lead. The verification SOP covers how to find out.
• Rock everywhere on the lot. Both rods may end up trenched; the 30 in depth and the 6 ft spacing still apply to each.
• A local amendment requiring a test, a specific spacing, or rods in a particular location; check before you lay out.

References

• NFPA 70, National Electrical Code, 2023 edition (2020 where noted), as adopted: 250.52(A)(3) and (A)(5), 250.53(A)(2) through (A)(4) (250.53(G) in 2017), 250.53(C), 250.53(D)(2), 250.64(B), (C) and (E), 250.66(A), 250.70
• State one-call (call-before-you-dig) law for your state
• See related: Grounding Electrode System Verification
• See related: Grounding Electrode Conductor Sizing Card
• See related: How to Bond the Water Pipe at the Service