Ground / Earthing rods (electrodes) are typically comprised of steel with a thin coating of copper or zinc (galvanized) to protect the steel from excessive corrosion. Copper-bonded ground rods are coated with copper with a thickness that ranges between 1.5 to 10 mils (0. to 0.010 inches). Galvanized ground rods are typically coated with zinc to a thickness of around 3.9 mils or 0. inches.

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When standard copper-clad carbon steel ground rods are installed, they are generally driven into the earth with a hammer or some other form of mechanical pounding device. The tensile strength of standard ground rods range from 58,000 psi to 90,000+ psi, which is important to prevent “mushrooming” of the head of the rod when hammering it into the earth. Some people call this the “drivability” of the ground rod. Stainless steel ground rods can have tensile strengths as high as 85,000 psi and typically can be driven into the earth similarly to a standard ground rod. Solid copper rods are often structurally too weak to be driven into the earth with a hammer system, thereby requiring pre-drilling. The hammering action scrapes the very thin copper coating off, exposing the steel to the corrosive soil. As such, the typical thin-coated copper-clad and galvanized ground rod can be expected to last between 10 to 13 years, depending upon the soil conditions. A copper-clad steel ground rod with a 10 mil (0.010 inches) copper coating is claimed to last as long as 30 years. Stainless steel and solid copper rods require no such coatings and as such have longer-life spans, easily exceeding 50+ years of service life.

Note: Galvanized ground rods tend to have shorter life spans in soil conditions where salt is present (copper-clad lasts longer when salt is in the soil).

Ground Rod Diameters

The diameter of the ground rod not only makes the “drivability” of the ground rod better, it also is the primary factor in determining the current-handling capacity of the ground rod, or “ampacity” of the electrode. If we look at IEEE Std.-142- Chapter 4.1.6 we see that the current-loading of a ground rod can be calculated with the following formula:

This can then be equated to show the ampacity of various electrodes in a given soil as shown in the chart below:

Electrode Ampacities in Various Soils.

A good “Rule of Thumb” is to say that a single ground rod can handle between 100 to 200 amps of current.

Ground Rod Spacing:
Ground rods should not be installed to close to each other. The Nature of Grounding Resistance of “sphere-of-influence theory” (IEEE Std.-142- Chapter 4.1.2), tells us that a given electrode will utilize a volume of soil around the electrode that is roughly equal to the length of the rod.

Nature of Grounding Resistance

This means that ground rods should be spaced outside of each other’s sphere-of-influence in order to maximize the benefits of the electrodes. In other words, you should not space electrodes so close that the sphere-of-influence of the first electrode falls within the sphere-of-influence of the adjacent rod.

For a 10-ft long ground rod, the closest the next ground rod should be spaced is 20-ft away.

The National Electrical Code (NEC) tells us that ground rods should be ideally spaced at a minimum distance of 2x their length. See NEC Article 250.53(A)(3) Informational Note.

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A Full Guide To Ground Rods

A ground rod, also known by the names earth rod and grounding electrode, is an electrode that is installed into the ground to create the path for grounding. It serves as the link between the ground neutral in the electrical system and Earth, intending to reduce the resistance between the two. 

A ground rod is an essential component of a proper grounding system. In the event of a fault, an adequate grounding system ensures that there's enough current flow to trip circuit breakers or blow fuses, disconnecting the faulty circuit.

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Ground rod is a long, slender metal rod made from a conductive material copper-bonded steel, solid copper, or galvanized steel. In this guide, we will look into the different types of ground rods on the market.

Types of Ground Rods

1. Copper-bonded steel ground rods: These are the most commonly used ground rods in many installations. They are made from steel cores coated with copper, which provides a good balance of strength (from the steel) and conductivity (from the copper).
2. Galvanized steel ground rods: Made of steel and coated with zinc for corrosion resistance. They are less conductive than copper rods but are more affordable. Use a galvanized steel ground rod in case you have budget constraints.
3. Solid copper ground rods: These rods are made entirely of copper. They offer excellent conductivity but are generally softer and more expensive than copper-bonded steel rods. Great for areas with high-corrosion potential and low-resistivity soils.
4. Stainless steel ground rods: These are used in special applications where extreme corrosion resistance is needed. Good for coastal areas and industrial settings.
5. Graphite ground rods: These are used in specific applications, especially in high-resistivity soils. They are more brittle than metal rods.
6. Tungsten ground rods: Used in rare and specific applications due to their cost, these rods offer a unique combination of properties. The applications include high-temperature environments, scientific facilities, nuclear facilities, telecommunications, aerospace, and military.
7. Chemical electrodes: These are not traditional 'rods,' but they are tube-shaped devices filled with salts that, when moistened, help improve the soil's conductivity around the electrode. They are used in areas with high soil resistivity.
8. Ufer grounds (concrete-encased grounding): Named after its inventor, Herbert G. Ufer, this isn't a rod but a grounding method involving embedding a grounding conductor in concrete. It's particularly effective in arid regions (drylands) with low natural soil conductivity.
9. Plate electrodes: Instead of rods, large conductive plates (often made of copper) can be buried in the ground to serve as grounding electrodes. They are used when soil conditions are not conducive to driving long rods.

Copper vs. Galvanized Steel Ground Rod

Now, let's compare the most popular ground rods: copper and galvanized steel. They are often compared because of how popular they are compared to other types. Here are the main points you should consider when choosing between copper and galvanized steel:

• Copper ground rod is more conductive compared to a galvanized steel rod.
• Both are resistant to corrosion, but copper ground rod is more resistant. The zinc coating of a galvanized ground rod can corrode in acidic soils.
• Galvanized steel ground rods have more strength, so they perform better in challenging installation conditions.
• The main advantage of a galvanized ground rod is the cheap cost.
• Copper ground rods have a longer lifespan.
• Copper ground rods are great for critical installations or where longevity is a priority. Galvanized ground rods are best for applications with budget constraints.

How To Install a Ground Rod?

Installing a ground rod properly is crucial for effective grounding. Here's a step-by-step guide to installing a ground rod:

Safety First: Always make sure to wear appropriate personal protective equipment (PPE) such as safety glasses, gloves, and sturdy footwear. Also, ensure you're not working near live electrical equipment or lines.

1. Choose the Location:

• Select a spot away from the building foundation, buried utilities, and other potential obstructions.
• Ensure the location complies with local electrical codes and regulations.

        2. Prepare the Ground Rod:

• If you're using sectional rods that need to be joined together, assemble them as per the manufacturer's instructions.
• Sharpen or taper the end of the rod if it isn't already. This makes it easier to drive into the ground.

        3. Drive the Rod:

• Hold the rod upright at your chosen location.
• Using a sledgehammer or a specialized ground rod driver, start driving the rod vertically into the ground. For greater ease and efficiency, especially for deep installations or hard soils, consider using power tools like an electric or pneumatic hammer drill with a ground rod driving attachment.
• Keep the rod as vertical as possible while driving. If the rod starts to bend, you can use a tool called a 'ground rod straightener' or withdraw the rod, straighten it, and restart.
• Drive the rod until it's flush with or just above the ground surface. Typically, ground rods are 6 to 10 feet long and should be driven almost entirely into the ground, leaving just a few inches exposed.

           4. Connect the Ground Wire:

• Use a grounding clamp or connector appropriate for the rod diameter and wire size.
• Attach one end of a thick copper grounding wire (often #6 or larger, but consult local codes) to the rod using the clamp. Make sure the connection is tight and secure.
• The other end of this wire will typically connect to the electrical service panel or the device/equipment you're grounding.

            5. Inspect and Test:

• Once installed, visually inspect your work to ensure the rod is secure and the wire connection is tight.
• For critical applications or as required by local codes, you should also measure the ground rod's resistance to Earth using a ground resistance tester. This ensures that the grounding system will function effectively.

             6. Backfill and Finish:

• If you had to dig up a significant amount of soil or if the ground around the rod was disturbed, backfill the area and compact the soil around the rod.

              7. Labeling (if required):

• Some jurisdictions or standards require that the grounding point be visibly marked or labeled. If so, place a label or marker indicating a ground rod below.

Important: Always check with local building codes and regulations before installing a ground rod. Some regions may have specific requirements or need permits for such installations. Also, consider using a utility locating service before you dig or drive anything into the ground to avoid damaging buried utilities.

Rules For Ground Rods

• Ground rods typically need to be at least 8 feet in length and have a minimum diameter of 5/8 inch, though 1/2 inch rods are acceptable if they are made of steel and copper-coated.

• Ground rods should be driven vertically into the ground to a depth of at least 8 feet. If obstructions, like rocks, prevent the rod from being driven vertically to the full depth, it can be driven at a 45-degree angle or buried horizontally in a trench at least 30 inches deep. A 4-foot ground rod is generally not considered sufficient for primary grounding purposes.

• The resistance to ground for a single ground rod should ideally be 25 ohms or less. If it's not, a second ground rod is typically required, spaced at least 6 feet apart from the first rod. The two rods are then bonded together with a grounding wire. If you are contemplating using one or two rods, follow this rule.

• Ground rods should be placed away from potential damage sources and should not be installed where they might puncture underground utilities.

• After installation and before backfilling any trenches, the grounding system should be inspected to ensure compliance with local codes.

NNC offers various types of ground rods.

Author Bio

Vita Chernikhovska

is a dedicated content creator at Nassau National Cable, where she simplifies complex electrical concepts for a broad audience. With over a decade of experience in educational content and five years specializing in wire and cable, her work has been cited by authoritative sources, including the New York Times. Vita's popular series, such as 'What is the amp rating for a cable size' and 'How to wire different switches and appliances,' make technical information accessible. She also interviews industry professionals and contributes regularly to the wire and cable podcast.

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