Quick Hits

📱 EPISODE 4 — Article 372 (1 of 1)
Cellular Concrete Floor Raceways — Full Article Breakdown!

SLIDE 1 — Scope & What It Is (372.1, 372.3)
🏗️ WHAT IS A CELLULAR CONCRETE FLOOR RACEWAY?
The hollow spaces in floors built from precast cellular concrete slabs, fitted with metal fittings that give access to the floor cells — common in high-rise office buildings.
🔌 Made up of floor cells (part of the structural floor), header ducts run at right angles to the cells (carrying conductors from cabinets into the cells), and junction boxes.
📌 Very similar in design/application to cellular METAL floor raceways (Article 374) — just built into precast concrete instead of sheet metal.
🚫 Reconditioned raceways AND reconditioned fittings are NOT permitted to be installed (372.3(B)).

SLIDE 2 — Uses Not Permitted + Header/Connection Rules (372.12, 372.18(A)–(B))
⛔ WHERE YOU CAN'T USE THEM (372.12)
1️⃣ Subject to corrosive vapor
2️⃣ Any hazardous (classified) location, unless another article allows it
3️⃣ Commercial garages — except supplying ceiling outlets or extensions below the floor (never above)
🔧 HEADER REQUIREMENTS (372.18(A))
🔹 Installed in a straight line at right angles to the cells
🔹 Mechanically secured to the top of the precast slab
🔹 End joints closed with a metal closure fitting, sealed against concrete entry
🔹 Electrically continuous throughout + bonded to the distribution center enclosure
🔌 CABINET CONNECTIONS (372.18(B))
Made using listed metal raceways and listed fittings only.

SLIDE 3 — Junction Boxes, Inserts & Markers (372.18(C)–(E))
📦 JUNCTION BOXES
Leveled to floor grade, sealed against water/concrete, metal, mechanically AND electrically continuous with the header.
🔩 INSERTS
Leveled, sealed, metal, fitted with grounded-type receptacles — an EGC or bonding jumper must connect the insert receptacles to a positive ground connection on the header. No chips/debris left in the raceway when cutting cell walls or access openings.
📍 MARKERS
Required for locating cells in the future.

SLIDE 4 — Conductors, Splices, Discontinued Outlets & Final Exam
📏 SIZE LIMIT (372.20)
No conductor larger than 1/0 AWG — unless special permission is granted.
📊 FILL LIMIT (372.22)
Combined cross-sectional area of conductors/cables ≤ 40% of the cell or header's cross-sectional area.
🌡️ AMPACITY (372.23)
Adjustment factors from 310.15(C) apply.
🔗 SPLICES & TAPS (372.56)
Only in header access units or junction boxes. Loop wiring (continuous unbroken conductor) does NOT count as a splice or tap.
🧹 DISCONTINUED OUTLETS (372.58)
Conductors feeding an abandoned/removed outlet must be pulled OUT of the raceway — no splices or re-insulated conductors left behind.

🎉 That's a wrap on Article 372 — Cellular Concrete Floor Raceways!

🧠 FINAL EXAM QUESTION FOR ARTICLE 372
Q: Per 372.18(D), what must connect the insert receptacles to a positive ground connection on the header?
A) A bare copper jumper only
B) An equipment grounding conductor or bonding jumper
C) The cell wall itself
D) A separate metal raceway
(Drop your final answer 👇)

Article 372 = DONE ✅ FOLLOW for more daily quick-hit NEC study notes ⚡ #JoshTheSparky #NEC2026 #ElectricianLife

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