?
Tuesday, December 8, 2020
Question:
Hello,
I'm a long time fan of the Code Question of the Day. Here's one that I need clarification on. What is the minimum-sized bonding jumper required for a metal water piping system (not a grounding electrode) if the largest ungrounded service entrance conductor is (10) 600 kcmil copper XHHW per phase?
Tommy Su
A
Answer:
Hello Tommy,
Thanks for the comments. The minimum-sized copper water bonding jumper required would be 3/0 copper or 250 kcmil aluminum or copper-clad aluminum. See NEC Section 250.104(A). This is based on the information provided in the question. The 2017 NEC would have required the 12.5% rule application, but in the 2020 NEC, the requirements were restored to the same as they were in 2014. The maximum size is not required to be larger than 3/0 copper or 250 aluminum or copper-clad aluminum.