Quick Hits

Episode 2: Supply Conductor Ampacity & Disconnecting Means (665.10 – 665.12)

SLIDE 1 (HOOK / COVER) ⚡ NEC Quick Hit: Sizing Induction Supply Conductors & Disconnects (Part 2) ⚡ 

How do you size conductors for machines with complex standby currents? Where must the heating equipment disconnect be located? Let's check out Sections 665.10 and 665.12! 👇

SLIDE 2 (SUPPLY CONDUCTOR AMPACITY) Factoring Standby Currents:

• Nameplate Calculation: Conductor ampacity must be not less than the sum of nameplate ratings for the largest group of machines capable of simultaneous operation, plus 100 percent of the standby currents of the remaining machines.

• Motor-Generator Units: Supply conductors for motor-generator equipment must follow Article 430 Part II rules.

SLIDE 3 (DISCONNECTING MEANS) Readily Accessible Cutoffs:

• Within Sight or Lockable: A readily accessible disconnecting means must be provided to disconnect each piece of heating equipment, located within sight from the controller or lockable open per Section 110.25.

• Rating: Must be rated at least equal to the full nameplate rating of the heating equipment.

SLIDE 4 (WRAP-UP) 💡 Apprentice Pro-Tip: 

When calculating feeder sizes for multiple induction heaters, don't forget to add the full standby current for idle machines that remain energized on the line. Overlooking standby load leads to overheated supply conductors!

💬 Save this post for your next industrial manufacturing facility design! 🔗 

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