Quick Hits

📱 EPISODE — Article 360

Flexible Metallic Tubing (FMT)

SLIDE 1 — What Is FMT?
🔧 THE DUCT-AND-PLENUM SPECIALIST

FMT is a specialized flexible raceway, particularly suited for wiring in ducts and air-handling spaces (per 300.25(B) and (C)) — it acts as an effective barrier to gases and combustion products. Very flexible, rarely affected by vibration or movement.

📋 Listing (360.2): FMT AND its fittings — both listed.

♻️ Reconditioned equipment (360.3): FMT and fittings are NOT permitted to be reconditioned and installed.

SLIDE 2 — Uses Permitted & NOT Permitted
✅ USES PERMITTED (360.10) — For branch circuits:
✅ Dry locations
✅ Concealed
✅ Accessible locations
✅ Max system voltage: 1000V AC / 1500V DC nominal

📌 The 1000V cap means FMT is OFF LIMITS for secondary circuits of sign ballasts/transformers, electronic sign power supplies, or oil burner ignition transformers — unless those circuits run under 1000V.

🚫 USES NOT PERMITTED (360.12)
❌ Hoistways
❌ Storage battery rooms
❌ Hazardous (classified) locations (unless another article permits)
❌ Underground direct burial, or embedded in poured concrete/aggregate
❌ Subject to physical damage
❌ Lengths OVER 6 ft (1.8m)

SLIDE 3 — Sizing & Bending Radii
📏 SIZE LIMITS (360.20)

Minimum: trade size ½ — Exceptions: trade size ⅜ for 300.25(B)/(C) duct applications, OR lengths ≤6 ft as part of a listed assembly/luminaire connection (410.117(C))
Maximum: trade size ¾ — MUCH smaller max than most raceways, reflecting FMT's specialized use case

🔄 BENDING RADII — TWO DIFFERENT TABLES depending on use:

Table 360.24(A) — Infrequent flexing (in service):
🔹 ⅜ in. → 10 in.
🔹 ½ in. → 12½ in.
🔹 ¾ in. → 17½ in.

Table 360.24(B) — Fixed bends (install only, no post-install flexing):
🔹 ⅜ in. → 3½ in.
🔹 ½ in. → 4 in.
🔹 ¾ in. → 5 in.

Notice how much bigger the radius needs to be for cable that will FLEX repeatedly in service vs. a one-time fixed installation bend.

SLIDE 4 — Grounding + Exam Question
🌎 GROUNDING (360.60)

FMT IS permitted as an equipment grounding conductor — but ONLY when installed per 250.118(A)(7).

🏷️ MARKING (360.120): per 110.21.

🎉 That wraps up Article 360 — Flexible Metallic Tubing!

🧠 TEST YOURSELF

Q: Per 360.12(6), what is the maximum length permitted for FMT?

A) 3 ft
B) 6 ft
C) 10 ft
D) There is no length limitation

(Drop your answer 👇)

Article 360 = DONE ✅ FOLLOW for more daily quick-hit NEC study notes ⚡ #JoshTheSparky #NEC2026 #ElectricianLife

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