Also a primary concern regarding enhanced grounding concretes is the use of carbon in the mix. However, some disadvantages are still evident.Īgain, these products do not increase the zone-of-influence and as such, the resistance-to-ground of the concrete encased electrode, is only slightly better than what a bare copper wire or driven rod would be in the ground. The most significant improvement of these new products is in reducing heat buildup in the concrete during fault conditions, which can lower the chances that steam will destroy the concrete encased electrode. The advantage of these products is that they are fairly effective in reducing the resistivity of the concrete, thus lowering the resistance-to-ground of the electrode encased. The most common are modified concrete products that incorporate conductive materials into the cement mix, usually carbon. There are many new products available on the market designed to improve concrete encased electrodes. Once the concrete cracks apart and falls away from the conductor, the concrete pieces act as a shield preventing the copper wire from contacting the surrounding soil, resulting in a dramatic increase in the resistance-to-ground of the electrode.
Many concrete encased electrodes have been destroyed, after receiving relatively small electrical faults. If the concrete encased electrode is not sufficient to handle the total current, the boiling point of the water may be reached, resulting in an explosive conversion of water into steam.
Concrete, by nature retains a lot of water, which rises in temperature as the electricity flows through the concrete. When an electrical fault occurs, the electric current must flow out of the conductor and through the concrete to get to the earth. However, the zone of influence is not increased therefore the resistance to ground is typically only slightly lower, than the wire would be without the concrete.Ĭoncrete encased electrodes also have some significant disadvantages. The advantages of concrete encased electrodes are that they dramatically increase the surface area and degree of contact with the surrounding soil. 4 AWG copper wire at least 20 feet in length and encased in at least 2 inches of concrete.
#Concrete encased electrode code
The National Electrical Code requires that Concrete Encased Electrodes use a minimum No. In today’s terminology, Ufer grounds consist of any concrete-encased electrode, such as the rebar in a building foundation, when used for grounding, or a wire or wire mesh encased in concrete. Originally, Ufer grounds were copper electrodes encased in the concrete surrounding ammunition bunkers. Similar environmental conditions, which lead to the failure of the driven rod, also plague the grounding plate, such as corrosion, aging, temperature, and moisture. This ultra-small zone of influence typically causes grounding plates to have a higher resistance reading than other electrodes of the same mass. The zone of influence of a grounding plate can be as small as 17 inches. While the surface area of grounding plates is greatly increased over that of a driven rod, the zone of influence is relatively small as shown in “B”. Grounding plates should be buried at least 30 inches below grade level. Grounding plates are typically placed under poles or supplementing buried ground rings. Ferrous materials must be at least 0.20 inches thick, while non-ferrous materials (copper) need only be 0.060 inches thick. The National Electrical Code requires that ground plates have at least 2 ft 2 of surface area exposed to the surrounding soil. Grounding plates are typically thin copper plates buried in direct contact with the earth.
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