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Episode 2: Arc Welder Conductors, OCPD & Secondary Grounding (630.11 – 630.15)
Episode 2: Arc Welder Conductors, OCPD & Secondary Grounding (630.11 – 630.15)
SLIDE 1 (HOOK / COVER)
⚡ NEC Quick Hit: Arc Welder Sizing & Secondary Grounding (Part 2) ⚡
How do you size supply conductors for intermittent arc welder duty cycles? Why is the secondary circuit not grounded like building wire? Let's break down Part II of Article 630! 👇
SLIDE 2 (CONDUCTOR AMPACITY & DUTY CYCLES)
Sizing Supply Conductors:
Effective Current ($I_{1\text{eff}}$): Supply conductor ampacity must be based on the $I_{1\text{eff}}$ value on the rating plate (or calculated using Table 630.11(A) duty-cycle multipliers).
Group Calculations: For multiple arc welders, minimum ampacity equals 100% of the two largest welders plus reduced percentages of the remaining units.
SLIDE 3 (OVERCURRENT PROTECTION & SECONDARY GROUNDING)
Protecting Circuits & Preventing Parallel Paths:
OCPD Cap: Arc welder OCPD is generally capped at not more than 200 percent of $I_{1\text{max}}$ or rated primary current.
Secondary Grounding Rule: Section 630.15 clarifies that welder secondary circuits (electrode and work cables) are not treated as premises wiring, meaning they are not required to be grounded as separately derived systems—preventing stray parallel current on equipment grounding conductors!
SLIDE 4 (WRAP-UP)
💡 Apprentice Pro-Duty: Grounding a welder's secondary circuit to building steel or nearby metal creates destructive parallel fault currents on your EGCs. Keep secondary welding circuits isolated from premises grounding!
💬 Save this post for your next industrial welding station hookup!
🔗 More code breakdowns at www.JoshTheSparky.com
⚠️ Educational NoticeQuick Hits are educational explanations based on my understanding of the NEC. Always verify requirements in the current adopted NEC, applicable local amendments, manufacturer instructions, and with the AHJ.
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