Services & DistributionQuestion 83 of 521
A single made rod electrode is measured at 40 ohms resistance to earth. The code requires that it be:
a.Left as is because 40 ohms is acceptable
b.Replaced with a copper water pipe
c.Bonded to the neutral only
d.Augmented with one additional electrode (or otherwise meet 25 ohms)
Explanation
Per 250.53(A)(2), a single rod, pipe, or plate electrode that does not have a resistance to earth of 25 ohms or less must be supplemented by one additional electrode. Because 40 ohms exceeds 25 ohms, a second electrode is required; leaving it or bonding only to the neutral does not comply.
Law Reference: 2023 NEC §250.53Practice all 521 questions free — no signup required.
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