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Tuesday, May 17, 2022
Question:
Hello and thanks for this great work. I read this every day. The question today is related to grounding electrodes. If there is a vapor barrier between the bottom of a concrete slab/footing, is a concrete-encased electrode still required?
Henry Hicks
A
Answer:
Hi Henry, and thanks for the kind remarks.
The answer to this question is found in Section 250.52(A)(3) and the definition of grounding electrode in Article 100. First, the definition indicates that a grounding electrode has to be in direct contact with the earth. A vapor barrier would prevent that. The informational note to 250.53(A)(3) indicates that concrete installed with insulation, vapor barriers, films, or similar items separating the concrete from the earth is not considered to be in “direct contact” with the earth. The installation described in your question would not qualify as a grounding electrode. The Code does not require that one be installed in this case but Section 250.50 indicates that all grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used. Hope this is useful.