Quick Hits

📱 EPISODE 1 — Article 344 (Part 1 of 2)

Rigid Metal Conduit (RMC) — Scope & Uses Permitted

SLIDE 1 — What Is RMC?
🔧 THE HEAVY-DUTY STANDARD

Rigid Metal Conduit (RMC) is thicker-walled than IMC — the classic "heavy pipe" conduit. Available in multiple materials: galvanized steel, PVC-coated steel, aluminum, red brass, and stainless steel.

📋 Listing (344.2): RMC, factory elbows/couplings, and fittings — all listed.

♻️ Reconditioned equipment (344.3): RMC, its factory elbows/couplings, and fittings are NOT permitted to be reconditioned and installed — same rule as IMC.

SLIDE 2 — Uses Permitted by Material Type (344.10(A))
✅ MATERIAL MATTERS HERE

🔹 Galvanized steel, PVC-coated steel, stainless steel, red brass → permitted under ALL atmospheric conditions and occupancies
🔹 Aluminum RMC → permitted where APPROVED for the environment (not automatic like the others)
🔹 Ferrous raceways/fittings protected ONLY by enamel → indoors only, NOT in severely corrosive occupancies

This is a bigger deal than with IMC — RMC's material options mean different rules apply to different types.

SLIDE 3 — Corrosive Environments & Cinder Fill (344.10(B)–(C))
🧪 CORROSION PROTECTION RULES

Galvanized steel/PVC-coated steel/stainless steel/red brass: permitted in concrete, direct earth contact, direct burial, or severe corrosive areas WHEN protected by approved corrosion protection.

Aluminum RMC: needs SUPPLEMENTARY corrosion protection when encased in concrete, in direct earth contact, or direct buried (must be identified for that application) — aluminum needs extra help that the other materials don't.

Cinder fill: galvanized steel, stainless steel, and red brass RMC (subject to permanent moisture) permitted IF protected by 2 in. noncinder concrete on all sides, buried 18+ in. under the fill, or protected by approved corrosion protection.

SLIDE 4 — Dissimilar Metals & Sizing + Exam Question
⚠️ GALVANIC ACTION RULES (344.14)

Avoid dissimilar metal contact where practicable. Notably: stainless steel/aluminum fittings CAN pair with galvanized steel RMC, AND galvanized steel fittings CAN pair with aluminum RMC (when not severely corrosive) — steel/aluminum interfaces show minor galvanic corrosion compared to same-metal-to-same-metal combos.

Stainless steel RMC has the SAME restrictive pairing list as stainless steel IMC (stainless fittings/boxes, steel boxes if not severely corrosive, approved accessories, bimetallic couplings).

📏 SIZE LIMITS (344.20)
🔹 Minimum: trade size ½ (Exception: trade size ⅜ permitted for motor lead enclosures per 430.245(B))
🔹 Maximum: trade size 6

🧠 TEST YOURSELF

Q: Per 344.10(B)(2), what is required for Aluminum RMC when encased in concrete or in direct contact with the earth?

A) Nothing additional — it's automatically approved
B) Approved supplementary corrosion protection
C) It cannot be used under these conditions at all
D) A PVC coating is mandatory in every case

(Drop your answer 👇)

FOLLOW — Part 2 wraps up bends, securing/supporting, couplings, and construction specs ⚡ #JoshTheSparky #NEC2026 #ElectricianLife

← View Chapter 3 Home

← Back To Article 344 Home

← Back To Quick Hits Home