Quick Hits

EPISODE 7 — Corrosion and Deterioration Protection over 1kva (305.16)

Slide 1 — Hook "Same corrosion-protection logic you learned in Article 300 — now applied to medium/high-voltage equipment."

Slide 2 — 305.16(A) Ferrous metal equipment

• Needs corrosion-resistant coating inside and out (stainless steel exempt); field-threaded conduit needs a conductive corrosion-resistant compound on the threads.

• Enamel-only protection can't go outdoors or in wet locations.

• Organic-coated boxes/cabinets marked "Raintight"/"Rainproof"/"Outdoor Type" ARE allowed outdoors.

• In concrete, direct earth contact, or severe corrosion areas: material or protection approved for that specific condition.

Slide 3 — 305.16(B), (C), (D)

• (B) Aluminum equipment embedded/encased in concrete or in direct earth contact needs SUPPLEMENTARY corrosion protection.

• (C) Nonmetallic equipment: needs approval for the condition — sunlight-exposed materials listed/identified as sunlight resistant; chemically exposed materials inherently resistant or identified for that specific chemical.

• (D) Indoor wet locations (dairy, laundry, cannery, frequently washed walls, damp absorbent surfaces): exposed wiring systems need at least ¼" airspace from the wall — except nonmetallic raceways/boxes/fittings on concrete/masonry/tile.

Slide 4 — Quiz + CTA Q: "Aluminum equipment embedded in concrete or in direct contact with earth needs what kind of protection?" A) No protection needed — aluminum doesn't corrode B) Supplementary corrosion protection C) Only a factory enamel coating D) Stainless steel cladding

✅ Answer: B — 305.16(B): supplementary corrosion protection is required in those conditions.

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