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Friday, February 18, 2022
Question:
Hello NEC Friends,
I always enjoy and learn reading this forum.... I have a follow on my question dated November 18, 2019. What is the rationale behind one conductor shall be "grounded" per 250.20(B)(1) and 250.26(1) if the whole idea is to trip the overcurrent protection device wherein the 2 conductors touch each other that would result into fault condition. The overcurrent protection device will still trip even 2 conductors are both ungrounded.
Jesus Santos
A
Answer:
Hello Jesus,
In addition to the overcurrent protective device clearing in a short-circuit condition (described in your question), having one conductor of a system that is grounded not only grounds the system but it establishes a ground-fault current path for the two ungrounded conductors should either one of them individually develop fault to ground or the grounded conductor. Section 250.20 indicates the systems that require grounding, 250.26 just established which conductor of the system is to be grounded.
Hope this is useful.