Quick Hits

Episode 2: Disconnecting Means & Conductor Sizing Math (660.6 – 660.9)

SLIDE 1 (HOOK / COVER) ⚡ NEC Quick Hit: X-Ray Disconnects & Feeder Math (Part 2 - Article 660) ⚡ 

How do you size supply conductors and disconnects for X-ray machines that fire in rapid, high-energy bursts? Section 660.6 and 660.7 give us the exact math formula. Let's break it down! 👇

SLIDE 2 (DISCONNECTING MEANS RATING)

Within Sight & Readily Accessible:

• Rating Formula: Disconnects must be rated for at least 50 percent of the momentary rating OR 100 percent of the long-time rating of the X-ray unit, whichever is greater!

• Location: Must be located readily accessible and within sight from the X-ray control panel.

SLIDE 3 (BRANCH-CIRCUIT & FEEDER CONDUCTOR MATH)

Sizing Conductors for Bursts:

• Branch-Circuit Conductors & OCPDs: Sized at not less than 50% of the momentary rating or 100% of the long-time rating (whichever is greater).

• Feeder Conductors (Multiple Units): Sized at 100% of the momentary demand rating of the two largest X-ray units plus 20% of the momentary ratings of all additional units!

SLIDE 4 (WRAP-UP)

💡 Apprentice Pro-Tip: Under Section 660.9, control and operating wires as small as 18 AWG or 16 AWG fixture wires are permitted for X-ray auxiliary circuits when protected by overcurrent protective devices rated not larger than 20 amperes!

💬 Save this post for your next industrial load calculation! 🔗 

More code breakdowns at www.JoshTheSparky.com

← View Chapter 6 Home

← Back To Article 626 Home

← Back To Quick Hits Home