Quick Hits

📱 EPISODE 1 — Article 334 (Part 1 of 3)

Type NM/NMC Cable ("Romex") — Scope & Where It's Permitted

SLIDE 1 — What Is NM/NMC Cable?
🏠 THE MOST FAMILIAR CABLE IN THE TRADE

Type NM (and NMC) cable — commonly called "Romex" — has been around since 1928, originally created as a replacement for knob-and-tube wiring and open wiring on insulators. Why it won out: continuous outer sheath protection, easy to fish through finished walls, no insulating supports needed, and only ONE hole needed per framing member.

📋 Listing (334.2): the cable itself, PLUS cable ties/staples/straps/hangers, AND connecting fittings — all must be listed and identified.

SLIDE 2 — Building Types Where It's Allowed (334.10)
🏗️ CONSTRUCTION TYPE MATTERS

NM/NMC is permitted in:
1️⃣ One- and two-family dwellings + attached/detached garages/storage buildings
2️⃣ Multi-family dwellings + detached garages (Types III, IV, V construction)
3️⃣ Other Types III/IV/V structures — IF installed within walls/floors/ceilings with a thermal barrier rated at least 15 minutes
4️⃣ Cable trays in Types III/IV/V structures (if identified for the use)
5️⃣ Types I/II construction — ONLY within permitted raceways

📌 Quick refresher: Type I/II = noncombustible construction; Types III/IV/V allow some or all combustible (wood) structural elements.

Exception to #3: nonhabitable grade-level storage garages/buildings under 1500 sq ft (Type V) don't need the 15-min thermal barrier.

SLIDE 3 — Type NM vs. Type NMC — What's the Difference?
🔀 TWO VARIANTS, DIFFERENT ENVIRONMENTS

Type NM (334.10(A)):
✅ Exposed AND concealed work — but ONLY in normally DRY locations
✅ Can be fished into air voids in masonry block/tile walls

Type NMC (334.10(B)):
✅ Exposed AND concealed work in dry, WET, damp, OR corrosive locations
✅ In outside/inside masonry block or tile walls
✅ In shallow chases in masonry/concrete/adobe — protected by a steel plate (min. 1/16 in. thick) and covered with plaster/adobe finish

💡 Think dairy barns or agricultural buildings — those need NMC because of ammonia fumes and corrosive conditions that would eat through regular NM.

SLIDE 4 — Where It's NOT Permitted + Exam Question
🚫 USES NOT PERMITTED (334.12) — BIG LIST

❌ Any structure not covered in 334.10(1),(2),(3),(5)
❌ Exposed in dropped/suspended ceilings (other than dwellings)
❌ AS service-entrance cable
❌ Commercial garages w/ hazardous classified locations
❌ Theaters (except 518.6(C))
❌ Motion picture studios, storage battery rooms
❌ Hoistways, elevators, escalators
❌ Embedded in poured cement/concrete/aggregate
❌ Hazardous classified locations (unless another article permits)
❌ Direct buried in earth
❌ Subject to physical damage

Plus NM-specific bans: corrosive fumes/vapors, embedded in masonry/concrete/adobe/plaster, shallow chases covered with finish, wet/damp locations (that's what NMC is for).

🧠 TEST YOURSELF

Q: Per 334.10(3), cables installed in Types III, IV, or V structures (other than dwellings) must be installed within walls/floors/ceilings providing a thermal barrier rated at least how long?

A) 10 minutes
B) 15 minutes
C) 30 minutes
D) 60 minutes

(Drop your answer 👇)

FOLLOW — Part 2 covers exposed work, bending radius, and support rules ⚡ #JoshTheSparky #NEC2026 #ElectricianLife

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