Quick Hits

Episode 2: Primary Protection & Lightning Exposure (742.10(A))

SLIDE 1 (HOOK / COVER) ⚡ NEC Quick Hit: Primary Protection & Lightning Rules (Part 2) ⚡ 

When does a communication circuit require a primary protector? From aerial drops to interbuilding cables, Section 742.10 spells out mandatory trigger conditions. Let's break down the rules! 👇

SLIDE 2 (PRIMARY PROTECTOR MANDATES)

When is Primary Protection Required?

• Aerial Runs: Any circuit run partly or entirely in aerial wire/cable not confined within a single block.

• High-Voltage Proximity: Any aerial or underground circuit exposed to accidental contact with power conductors operating at over 300 volts to ground.

• Interbuilding Runs: Each end of an interbuilding circuit on a premises where lightning exposure exists.

SLIDE 3 (WHAT COUNTS AS "LIGHTNING EXPOSURE"?)

Exceptions to Lightning Risk:

• Circuits in dense metropolitan areas with high-rise buildings that intercept lightning.

• Interbuilding underground cable runs of 140 ft (42 m) or less housed in continuous grounded metal conduit or metallic shields connected to electrode systems.

• Regions with 5 or fewer thunderstorm days per year (like the Pacific Coast).

SLIDE 4 (WRAP-UP)

💡 Apprentice Pro-Tip: Interbuilding communications runs without a continuous grounded metallic shield must have primary protectors installed at both ends of the cable to protect equipment in both structures!

💬 Save this post for your next campus or commercial interbuilding cable run! 🔗 

More code breakdowns at www.JoshTheSparky.com

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