Quick Hits

EPISODE 4 — Outdoor Overhead Conductors & Engineered Support Requirements (267.20, 267.21)

Slide 1 — Hook "Today: a wiring method that's outdoor-only, and the heavy engineering documentation this article demands for support structures."

Slide 2 — 267.20 Outdoor overhead conductors

• Single conductors (insulated, covered, or bare) can be installed OUTDOORS as open wiring on support structures — but ONLY for systems over 1000V AC / 1500V DC. This method is NEVER permitted indoors.

Slide 3 — 267.21 Support — a licensed PE has to sign off

• Conductor spacing: needs documented engineering design by a licensed professional engineer, available to the AHJ on request, considering: applied voltage, conductor size, distance between structures, structure type, wind/ice loading, and surge protection.

• Structures: same PE documentation requirement, considering soil conditions, foundations, total supported weight, weather loading (ice/wind/temp/lightning), direction-change angles, span distances, dead-end effects, guy wire/anchor strength, structure size/material, and hardware.

• Insulators: must be rated for applied phase-to-phase voltage, required mechanical strength, and impulse withstand (BIL) per Table 495.24.

Slide 4 — Quiz + CTA Q: "Who must document the engineered design for conductor spacing and support structures under 267.21?" A) Any qualified electrician B) A licensed professional engineer engaged primarily in designing such systems C) The local AHJ D) Documentation isn't required

✅ Answer: B — 267.21(A) & (B) both require a licensed PE's documented design.

CTA: Follow for more daily quick-hit study notes 📚⚡

← View Chapter 2 Home

← Back To Article 266 Home

← Back To Quick Hits Home