Services, Grounding & Bonding第 50 / 120 题
When a metal underground water pipe is used as a grounding electrode, what else is required?
a.It must be bonded to the gas piping system as the supplement
b.No supplement is required if the pipe is longer than 20 feet
c.It must be supplemented by an additional electrode of a type identified in 250.52
d.It may be used only if the resistance to earth is 25 ohms or less
解析
A water pipe electrode is never allowed to stand alone because plastic repairs or dielectric fittings can silently disconnect it from earth, so it must always be supplemented by another qualifying electrode such as a rod or a concrete-encased electrode. Pipe length does not remove the requirement, gas piping is bonded but is not permitted as an electrode, and the 25-ohm test applies to rod, pipe and plate electrodes.
法律依据: 2023 NEC §250.53(D)(2)免费刷完整 120 道题库 — 无需注册。
同考点相关题目
- A single ground rod does not have to be supplemented by a second electrode if its resistance to earth does not exceed what value?
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