Question: To comply with NEC requirements, a driven ground rod must have a resistance of ____ ohms or less.
- 10
- 20
- 25
- None of the above
See the answer below.
Answer: D
Explanation: Section 250.53 of the NEC requires that any made electrode that has a resistance greater that 25 ohms be supplemented by another electrode. The NEC does not require that an electrode have a resistance of 25 ohms or less, even after the addition of the supplemental electrode. It is worth noting though that many project specifications may have more restrictive requirements.
Lupacchino is a senior design engineer with Gaylor Electric, Inc. in Noblesville, Ind. and serves as an alternate on NEC Code-Making Panel No. 3. He is currently licensed in more than 80 jurisdictions. He can be reached at [email protected].