Quick Hits

PART II — OVERHEAD SERVICE CONDUCTORS

EPISODE 4 — Sizing, Attachment, Roof Supports and Surge Arresters over 1kva (268.23–268.29)

Slide 1 — Hook "New Part! Overhead service conductors — how they're sized, attached, supported over roofs, and protected from surges."

Slide 2 — 268.23 Sizing

• Services supplying ONLY transformers: ampacity ≥ the sum of the transformers' nameplate ratings.

• Services supplying transformers PLUS utilization equipment: ampacity ≥ transformer nameplate sum + 100% of the utilization equipment's simultaneous designed load.

• Supervised installations: qualified persons under engineering supervision can determine sizing themselves (same "supervised installation" concept you've seen elsewhere in medium-voltage articles).

Slide 3 — 268.26–268.29

• 268.26 Point of attachment: must meet the clearance rules of 267.19, and can never be lower than 10 ft above finished grade.

• 268.27 Means of attachment: conductors attach to noncombustible, nonabsorbent insulators securely fastened to the structure.

• 268.28 Roof supports: conductors crossing a roof need substantial, independent support (where practicable); if the substantial structure is metal on a grounded system, it must be bonded to the grounded overhead service conductor with a jumper and listed connector.

• 268.29 Surge arresters: permitted on each ungrounded overhead service conductor per Article 242 Parts II & III (surge arresters used to be called "lightning arresters" in older references).

Slide 4 — Quiz + CTA Q: "What's the minimum height above finished grade for the point of attachment of overhead service conductors?" A) 8 ft B) 10 ft C) 12 ft D) 15 ft

✅ Answer: B — 268.26: never less than 10 ft (3.0 m) above finished grade.

CTA: Follow for more daily quick-hit study notes 📚⚡ — Part II done! Part III (Underground) is next.

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