What is the minimum length of bare copper conductor (or rebar) required for a concrete-encased electrode ("Ufer ground") to qualify as a grounding electrode?
Not quite. The answer is D: 20 feet
250.52(A)(3) requires at least 20 feet of either 1/2-inch (or larger) rebar or bare copper conductor not smaller than 4 AWG, encased in at least 2 inches of concrete near the bottom of a foundation or footing in direct contact with the earth. Confusing this 20-foot minimum with the 8-foot ground-rod length is a common mix-up.
Reference: NEC 2023 250.52(A)(3) (Concrete-Encased Electrode)
Checked against multiple published sources
Two independent secondary sources agree on the requirement; neither is the code text. The ECM source is an older article that names no edition; the 20 ft, 1/2 in. rebar and 2 in. cover figures agree across both.
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