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Monday, June 26, 2017
Question:
Charlie,
Until the NEC is written in English, I have another question for you.
I have three scenarios: 1) New construction with copper water service, concrete footing re-rod ground; 2) New construction with plastic water service, concrete footing re-rod ground; 3) Old construction with copper water service and no concrete footing re-rod ground.
For 1), 2), 3), are ground rods required and, if 25 ohm resistance is not confirmed, is a second ground rod required?
I would contribute to a fund to pay a good technical writer to re-write the NEC so any two readers can come to the same conclusion. Of course, you would be out of a job.
Dave
A
Answer:
Hey Dave thanks for your questions. All grounding electrodes - that meet the conditions described in 250.52 A)(1) through (A)(7) must be bonded together to create a grounding electrode system as stated in 250.50.
Scenario 1. The metal underground water pipe must be bonded to the concrete encased electrode and be used as the grounding electrode system. No additional electrodes are required.
Scenario 2. The concrete encased electrode is sufficient as the grounding electrode system. No additional electrodes are required.
Scenario 3. The metal underground water pipe must be supplemented by one or more electrodes described in 250.52(A)(2) through (A)(8) as stated in 250.53(D)(2). If a ground rod is used to supplement the water pipe it must meet 250.53(A) - either two ground rods or determine that a single ground rod has a resistance to earth of not more than 25 ohms.
I'm OK with being out of a job; I'm hoping to become a "pool boy" for a rich single woman. You can be one of the technical writers by submitting clear wording for the 2020 NEC by September 7 of this year.