Quick Hits

PART III — UNDERGROUND SERVICE CONDUCTORS

EPISODE 5 — Underground Service Conductor Installation, Sizing, Damage Protection & Splicing (268.30–268.33)

Slide 1 — Hook "New Part! Everything about running service conductors underground at medium/high voltage."

Slide 2 — 268.30 Installation

• Underground service conductors must be insulated for the applied voltage — EXCEPT specific bare-copper/bare-aluminum allowances for raceway use, approved soil conditions for direct burial, or as part of a listed underground cable assembly.

• Approved wiring methods: RMC, IMC, nonmetallic underground conduit with conductors (NUCC), HDPE conduit, PVC, RTRC, direct-burial-rated Type MV/MC cable, or Type TC-ER cable rated and identified for both the voltage and service/direct-burial use.

Slide 3 — 268.31, 268.32, 268.33

• 268.31 Sizing: same three-path logic as overhead (transformer-only load / transformer+utilization load / supervised installation) — PLUS a hard minimum of 8 AWG copper or 6 AWG aluminum/copper-clad aluminum, and the grounded conductor can't be smaller than what 250.24(D) and Article 270 require.

• 268.32 Damage protection: underground conductors protected per 305.15; where they enter a building, they follow 268.62 or a raceway method from the 268.43 service-entrance list.

• 268.33 Splices: service conductors CAN be spliced/tapped, following 110.40, 268.46, and the applicable 305.15/305.23/305.25 rules.

Slide 4 — Quiz + CTA Q: "What's the minimum size for underground service conductors (copper)?" A) 10 AWG B) 8 AWG C) 6 AWG D) 4 AWG

✅ Answer: B — 268.31(D): not smaller than 8 AWG copper (6 AWG aluminum/copper-clad aluminum).

CTA: Follow for more daily quick-hit study notes 📚⚡ — Part III complete! Part IV (Service-Entrance Conductors) is next — a bigger one.

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