![]() ![]() Actual contact between the marbles and the driven rod will be very small. This is especially true in rocky soils, in which the rod will only make contact on the edges of the surrounding rock.Ī good example of this is to imagine a driven rod surrounded by large marbles. Driven rods also have a very small surface area, which is not always conducive to good contact with the soil. Environment, aging, temperature and moisture also easily affect driven rods, giving them a typical life expectancy of five to 15 years in good soil conditions. Additionally, the act of driving the rod into the soil can damage the copper cladding, allowing corrosive elements in the soil to attack the bared steel and further decrease the life expectancy of the rod. When an electrical current is imposed, electrolysis will occur. ![]() Generally speaking, galvanized rods are a better choice in all but high salt environments.Īn additional drawback of the copper-clad driven rod is that copper and steel are two dissimilar metals. 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 for prolonging the life of the grounding rod and grounding systems. Many corrosion problems can occur because copper is not always the best choice in corrosion protection. While copper is certainly a conductive material, its real purpose on the rod is to provide corrosion protection for the steel underneath. ![]() Many industrial specifications require this length as a minimum.Ī common misconception is that the copper coating on a standard driven rod has been applied for electrical reasons. The most common rods used by commercial and industrial contractors are 10 ft in length. Typically, a shovel is used to dig down into the ground 18 inches before a driven rod is installed. The National Electric Code (NEC) 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. 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. 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.īecause 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. Driving these rods can be extremely labor-intensive when rocky terrain creates problems as the tips of the rods continue to mushroom. Mushrooming can occur on both the tip of the rod, as it encounters rocks on its way down, and the end where force is being applied to drive the rod through the earth. The steel used in the manufacture of a standard driven rod tends to be relatively soft. The driven rod has been in use since the earliest days of electricity with a history dating as far back as Benjamin Franklin.ĭriven rods are relatively inexpensive to purchase, however ease of installation is dependent upon the type of soil and terrain where the rod is to be installed. This is by far the most common grounding device used in the field today. 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. It is important to know that aluminum electrodes are not allowed for use in grounding. The National Electric Code requires that the grounding electrodes be tested to ensure that they are under 25-ohms resistance-to-ground (Earth). Grounding is the process of electrically connecting any metallic object to the earth by the way of an earth electrode system. ![]()
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