Quick Hits

Article 378 (Part 1 of 2)
Nonmetallic Wireways — Full Article Breakdown!

SLIDE 1 — Scope, Listing & Reconditioned Equipment (378.1, 378.2, 378.3)
🏗️ WHAT IS A NONMETALLIC WIREWAY?
Covers use, installation, and construction specs for nonmetallic wireways and their associated fittings.
✅ Must be LISTED — both the wireway AND its associated fittings (378.2).
🚫 Reconditioned nonmetallic wireways AND reconditioned fittings are NOT permitted to be installed (378.3(B)).

SLIDE 2 — Uses Permitted (378.10)
✅ WHERE YOU CAN USE THEM
1️⃣ ONLY exposed work (except as permitted in #4 below)
2️⃣ Corrosive environments — if identified for the use
3️⃣ Wet locations — if listed for the purpose
⚠️ Extreme cold can make nonmetallic wireway brittle and more prone to physical damage.
4️⃣ As extensions passing transversely through walls — if the in-wall section is unbroken and conductors stay accessible on BOTH sides

SLIDE 3 — Uses Not Permitted (378.12)
⛔ WHERE YOU CAN'T USE THEM
1️⃣ Subject to physical damage
2️⃣ Hazardous (classified) locations — unless another article permits it
3️⃣ Exposed to sunlight — unless listed and marked suitable for that purpose
4️⃣ Ambient temperatures outside the wireway's listing
5️⃣ Conductors whose insulation temperature rating exceeds what the wireway is listed for

SLIDE 4 — Conductors: Parallel, Size & Fill (378.20, 378.21, 378.22) + Final Exam
🔗 PARALLEL CONDUCTORS (378.20)
Single conductor cables run in parallel per 310.10(G) → grouped with no more than ONE conductor per phase/neutral/grounded conductor (prevents current imbalance from inductive reactance).
📏 SIZE LIMIT (378.21)
No conductor larger than the wireway is designed for.
📊 FILL & ADJUSTMENT FACTORS (378.22)
Combined cross-sectional area of conductors/cables ≤ 20% of the interior cross-sectional area — 310.15(C)(1) adjustment factors apply up to that 20% fill (signaling/starting-duty motor control conductors don't count as current-carrying).

🧠 FINAL EXAM QUESTION FOR ARTICLE 378 (Part 1)
Q: Per 378.10(1), nonmetallic wireways are permitted ONLY for what type of work, except as permitted elsewhere in that section?
A) Concealed work
B) Exposed work
C) Underground work
D) Direct burial work
(Drop your final answer 👇)

Article 378 Part 1 = DONE ✅ Part 2 drops next — insulated conductors, support, expansion, splices & marking! ⚡ #JoshTheSparky #NEC2026 #ElectricianLife

← View Chapter 3 Home

← Back To Article 378 Home

← Back To Quick Hits Home