What are driven rods and advanced driven rods?
The standard driven rod or copper-clad rod consists of an 8 to 10 foot length of steel with a 5 to 10-mil coating of copper. This is by far the most common grounding device used in the field today.
The Driven Rod
The standard driven rod or copper-clad rod consists of an 8 to 10 foot length of steel with a 5 to 10-mil coating of copper. This is by far the most common grounding device used in the field today. The driven rod has been in use since the earliest days of electricity, with a history dating as far back as Benjamin Franklin.
Driven rods are relatively inexpensive to purchase, however, ease of instal can be extremely labor-intensive, when rocky terrain creates problems as the tips of the rods will continue to mushroom. Often, these rods will hit a rock and actually turn back around on themselves and pop back up a few feet away from the installation point.
The National Electrical Code requires that the grounding electrodes be tested to ensure that they are under 25 ohms resistance-to-ground (earth). It is important to know that aluminum electrodes are not allowed for use in grounding (earthing) as aluminum will rapidly corrode when buried.
Because driven rods range in length from 8 to 10 feet, a ladder is often required to reach the top of the rod, which can become a safety issue. Many falls have resulted from personnel trying to literally ‘whack’ these rods into the earth, while hanging from a ladder many feet in the air.
The National Electrical Code requires that driven rods be a minimum of 8 feet in length and that 8 feet of length must be in direct contact with the soil. To comply with this requirement the installer will typically use a shovel to dig down into the ground 18 inches before a driven rod is installed, although the most common rods used by commercial and industrial contractors today are rods 10 ft in length, which negates the need for the extra installation process. This can save time as well as meet with the many industrial specifications that also require this length as a minimum.
A common misconception is that the copper coating on a standard driven rod has been applied for electrical reasons. While copper is certainly a conductive material, its primary purpose on the rod is to provide corrosion protection for the steel underneath. Corrosion problems can occur because copper is not always the best choice for corrosion protection. It should be noted that galvanized driven rods have been developed to address the corrosion concerns that copper presents, and in many cases are a better choice in prolonging the life of the grounding rod and grounding systems. Generally, galvanized rods are a better choice in all but high salt environments.