This is an important consideration in view of some of the modern building methods in use. In such a case, the concrete-encased electrode is not present, and another suitable electrode must be used. This note explains that when such materials are encountered that insulate the concrete from the earth, the "direct contact" with the earth required for the use of a concrete encased electrode has been lost. 2).Ī new informational note has been added to 250.52(A)(3) to clarify how a concrete-encased electrode is impacted by the use of insulation, vapor barriers, films, or similar items that separate the concrete from the earth. of concrete and located inside the concrete footing or foundation that is in direct contact with the earth ( Fig. These rebar or this conductor must be encased by at least 2 in. This is an electrode developed by using electrically conductive reinforcing bars or bare copper conductors not smaller than 4 AWG at least 20 ft in length. The requirements for a concrete-encased electrode, commonly called a "Ufer Ground" are included in 250.52(A)(3). The 2011 NEC no longer allows the structural metal to serve as a grounding electrode when supplemented by a ground rod. The concrete-encased electrode must comply with the requirements of 250.52(A)(3), and the hold-down bolts must be connected to the concrete-encased electrode by means of welding, exothermic welding, the usual tie wires used to secure the rebar in a footing, or other approved means ( Fig. The hold-down bolts securing the structural steel column that are connected to a concrete-encased electrode are considered to provide a satisfactory earth connection. When the structural metal is in direct earth contact for 10 ft or more, with or without concrete encasement, it is considered to be connected to the earth and is acceptable for use as a grounding electrode. The 2011 NEC has once again revisited the rule explaining when a structural metal building frame can serve as a grounding electrode.
Concrete encased electrode code#
Quinn, M.J.: Parallel Programming in C with MPI and OpenMP.The use of structural metal as a grounding electrode is an issue that has been revised during several recent Code cycles. In: Proceedings of the International Conference on Grounding and Earthing, GROUND 2004, Belo Horizonte, Brazil, pp. The MIT Press, London (1996)īirchal, M.A.S., Vale, M.H.M., Visacro, S.F.: Analysis of Risk Conditions on Interconnected Grounding Systems: Concrete Encased Electrodes and Grid. Snir, M., Otto, S., Lederman, S.H., Walker, D., Dongarra, J.: MPI: The Complete Reference. In: Proceedings of the International Conference on Grounding and Earthing - GROUND 2000, Belo Horizonte, Brazil, pp. Visacro, S.F., Ribeiro, H.A., Palmeira, P.F.M.: Evaluation of Potential Distribution at Vicinities of Grounding Configurations Comprising Both Concrete Encased Electrodes and Conventional Meshes. Kostic, M.B., Popovic, B.D., Jovanonic, M.S.: Numerical Analysis of a Class of Foundation Grounding Systems. M.SC Thesis, UFMG, Belo Horizonte, Brazil (2000) (in Portuguese) Ribeiro, H.A.: Development of a Computational Tool for the Performance Evaluation of the Concrete Encased Grounding Systems Over Low Frequency Phenomena. In: Proceedings of the International Conference on Grounding and Earthing, GROUND 1998, Belo Horizonte, Brazil, pp. Visacro, S.F., Ribeiro, H.A.: Some Evaluations Concerning the Performance of Concrete-Encased Electrodes: an Approach by the Boundary Elements. Ufer, H.G.: Investigation and Testing of Footing-Type Grounding Electrodes for Electrical Installations.
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