Quick Hits

EPISODE 8 — Temperature Extremes, Mixing with Other Systems & Wet Raceways Above Grade (300.9, 300.10, 300.11)

Slide 1 — Hook "Today: condensation in raceways, why electrical raceways can't double as plumbing, and wet-location raceways above grade."

Slide 2 — 300.9 Raceways exposed to different temperatures

• Where parts of a raceway/sleeve see different temperatures (cold storage areas, interior-to-exterior transitions) and condensation is a known problem: seal the raceway to stop warm air circulating into the colder section (using sealants identified for the components involved — no explosionproof seal needed), OR use a listed fitting/approved means designed to prevent condensation (like a thermal break coupling).

• Expansion/deflection fittings are also required wherever needed to handle thermal expansion, deflection, and contraction in raceways.

Slide 3 — 300.10 & 300.11

• 300.10: raceways/cable trays containing electrical conductors CANNOT also contain any pipe/tube for steam, water, air, gas, drainage, or any non-electrical service. Keep electrical and mechanical systems separate.

• 300.11: raceways installed in wet locations ABOVE grade have their interior automatically classified as a wet location too — conductors/cables need to comply with 310.10(C), and the raceway must be arranged to drain.

Slide 4 — Quiz + CTA Q: "Can an electrical raceway also contain a water pipe running through it?" A) Yes, if properly sealed B) No — raceways can't contain non-electrical service pipes/tubes C) Only for raceways over 4 in. trade size D) Only outdoors

✅ Answer: B — 300.10 flatly prohibits mixing electrical raceways with pipes for other services.

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