Ground Rods
How Many Ground Rods Do You Need? NEC 250.53 Two-Rod Rule, the 25 Ohm Test, Soil Resistivity and Rod Spacing, Length and Diameter
When one rod is enough, when the NEC requires two, why almost every inspector now requires two without a test, how soil resistivity sets electrode resistance, and how rod length, diameter and spacing change the result, with the formula and a table.
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