Thu, 2011-10-20 11:44
Q. When a metal water pipe is used as a grounding electrode, is the concrete encased electrode satisfactory as the supplemental electrode, or is a ground rod still required?
A. When an underground metal water pipe grounding electrode is present [250.52(A)(1)], it must be supplemented by one of the following electrodes [250.53(D)(2)]:
- Metal frame of the building/structure electrode [250.52(A)(2)]
- Concrete-encased electrode [250.52(A)(3)]
- Ground ring electrode [250.52(A)(4)]
- Ground rod electrode meeting the requirements of 250.52(A)(5)
- Other listed electrodes [250.52(A)(6)]
- Metal underground systems, piping systems, or underground tanks [250.52(A)(8)]
The termination of the supplemental grounding electrode conductor must be to one of the following locations (see Figure):
- Grounding electrode conductor
- Service neutral conductor
- Metal service raceway
- Service equipment enclosure
: The supplemental electrode is permitted to be bonded to interior metal water piping located not more than 5 ft from the point of entrance to the building/structure [250.68(C)(1)].