Quick Hits

Episode 4: Overcurrent Protection, Control & Bonding (610.41 – 610.61)

SLIDE 1 (HOOK / COVER) ⚡ NEC Quick Hit: Overcurrent Protection & Bonding (Part 4) ⚡ 

Do crane trolley wheels count as equipment grounding conductors? How are motor branch circuits protected? Let's finish Article 610! 👇

SLIDE 2 (BRANCH-CIRCUIT & OVERLOAD PROTECTION)

Protecting Motors and Taps:

• Short-Circuit Protection: Crane motor branch circuits are protected by fuses or inverse-time circuit breakers sized per Section 430.52.

• Motor Overload: Individual motor overload protection is required (though small hoists under 7.5 hp under manual control have specific exceptions).

SLIDE 3 (BONDING THE BRIDGE & TROLLEY FRAME)

The Separate EGC Mandate:

• No Wheel Grounding: The bridge frame and trolley frame shall not be considered electrically bonded through bridge and trolley wheels resting on their metal tracks! (Dirt and grease impede reliable contact).

• Separate Bonding Conductor: A separate equipment grounding conductor (per Section 250.118) must be run with the circuit conductors to bond all non-current-carrying metal parts together into an effective ground-fault current path.

SLIDE 4 (WRAP-UP)

💡 Apprentice Pro-Tip: Metal-to-metal bearing surfaces of moving parts are considered naturally bonded, but never rely on wheel-to-rail contact for grounding safety. Always pull a dedicated bonding conductor!

💬 Save this post for your final code review on cranes and hoists! 🔗 

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