Services, Grounding & BondingQuestion 47 of 120
A single ground rod does not have to be supplemented by a second electrode if its resistance to earth does not exceed what value?
a.5 ohms
b.25 ohms
c.100 ohms
d.1 ohm
Explanation
A single rod, pipe or plate electrode must be supplemented unless it is shown to have a resistance to earth of 25 ohms or less. Values such as 5 ohms or 1 ohm come from specialized standards for communications and lightning systems, not from this general requirement, and 100 ohms is far too high.
Law Reference: 2023 NEC §250.53(A)(2)Practice all 120 questions free — no signup required.
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