![]() ![]() Ufer on twenty-four buildings located in Arizona, beginning in 1942. These concepts came about primarily as a result of the work of Mr. ![]() The steel reinforcing bar concrete-encased electrode was first introduced in the 1975 NEC. Since most foundations and footing are constructed in the horizontal position, this would imply that only a horizontally installed concrete-encased electrode would comply with the previous requirements of Section 250.52(A)(3).Ĭoncrete-encased electrodes were first introduced into the NEC in the 1968 edition with the 4 AWG copper conductor concept. In the past, this section of the NECaddressed only that section of a concrete-encased electrode that was located within and near the bottom of a concrete foundation or footing that was in direct contact with the earth. A close-up look at a vertical concrete-encased electrode Some History about Concrete-Encased Electrodes With this story as our backdrop, let’s take a look at some of the changes to the 2008 NECpertaining to concrete-encased electrodes and, in particular, Section 250.52(A)(3). The rules of the 2005 NECare satisfied, and everyone lives happily ever after…yeah, right! ![]() This lightning-generated current, having full knowledge of the rules of the National Electrical Code, knowing that it can only take horizontal paths of concrete-encased electrodes and that vertical paths are not recognized, abruptly reverses its path to avoid this vertical pier. Something strange and unusually unexpected happens at this point. Traveling horizontally along the footings that are now performing double-duty as a structural component and concrete-encased electrode, this menacing surge of current suddenly encounters a vertical path in the form of a pier doing the same job it’s done since the day it was poured, helping to support the foundation. Traveling past the service equipment, finding solace with the grounded conductor and the main bonding jumper, this current finds its way onto the grounding electrode conductor leading directly to the concrete-encased electrode. With this entire scenario taking place quicker than the blink of an eye, the largest amount of this current finds little resistance traveling along the path of the reliable concrete-encased electrode. Some of this unwanted current takes the path of the metal water piping system to reach its ultimate destination, while other amounts of current find a hardy route to ground in the form of that ground rod driven below the service that the homeowner silently cursed every time he ran over it with his lawnmower. This overcurrent, perhaps as much as one million volts, is looking to go to ground and will take all paths available, with the paths of least resistance sustaining the most current. Our grounding electrode system immediately jumps into action. The overhead service mast, sticking straight up in the air as if to defy the surrounding atmosphere, abruptly takes a direct hit by lighting. Vertically positioned concrete-encased electrodes, such as this pier, are now recognized by NEC-2008 if all of the conditions of 250.52(A)(3) are met. Now the lights are out, along with the rest of the electricity that we too often take for granted until times like this. Will they stay on or go out? On again, off again. The lights inside this comfort-giving dwelling unit start to flicker. That distant thunder is suddenly not so distant and is now all around with almost deafening crackling from the skies to the ground (or is it ground to sky)? Suddenly, without warning, the rain intensifies and the skies turn darker and darker. The skies were a cloudy gun-barrel gray as the light rain fell and the thunder rolled in the distant background. It was a typical spring afternoon in this typical Midwest town of Anywhere, USA.
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