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📱 EPISODE 2 — Article 330 (Part 2 of 3)

Installation Details — Bending, Securing & Supporting

SLIDE 1 — Exposed Work & Framing Members (330.15, 330.17, 330.23)
📍 INSTALLATION LOCATION RULES

Exposed runs (330.15): must closely follow the building finish surface or running boards. Can be run on the underside of joists IF supported at each joist and protected from physical damage.

Through/parallel to framing members (330.17): protect per 300.6(A), (C), and (D).

Accessible attics (330.23): follow 320.23 — guard strips required where cable crosses joists or is within 7 ft of the floor across rafters/studs (or within 6 ft of a scuttle hole if the attic isn't permanently accessible).

SLIDE 2 — Bending Radius (330.24)
📐 THREE DIFFERENT RULES DEPENDING ON SHEATH TYPE

Smooth sheath:
🔹 ≤¾ in. diameter → 10x the sheath diameter
🔹 >¾ in. to 1½ in. → 12x the sheath diameter
🔹 >1½ in. → 15x the sheath diameter

Interlocked-type armor or corrugated sheath: 7x the sheath diameter

Shielded conductors: 12x the individual conductor diameter, OR 7x the overall multiconductor cable diameter — whichever is GREATER

📌 Different sheath = different bend math. This is a classic multi-part exam trap.

SLIDE 3 — Securing & Supporting (330.30)
🛠️ SECURING vs. SUPPORTING — THEY'RE DIFFERENT THINGS

Permitted securing/support methods: listed cable ties, staples, cable cleats, straps, hangers, or other approved means that won't damage the cable. MC fittings/connectors can also serve as support.

📏 General intervals: secure AND support at intervals not exceeding 6 ft (1.8m)
📏 Near terminations: cables with 4 or fewer conductors ≤10 AWG must be secured within 12 in. (300mm) of every box/cabinet/fitting
📏 Vertical runs: listed cables with ungrounded conductors 250 kcmil+ can be secured at intervals up to 10 ft (3m)

SLIDE 4 — Unsupported/Unsecured Exceptions + Exam Question
🔓 WHEN MC CABLE DOESN'T NEED SUPPORT (330.30(D))

Three exceptions:
1️⃣ Fished through concealed spaces in finished buildings where supporting is impractical
2️⃣ ≤6 ft from last support point to a luminaire/equipment connection, within an accessible ceiling
3️⃣ Interlocked-armor MC, ≤3 ft (900mm) from last secure point, connecting equipment needing flexibility (vibration isolation or movement)

🧠 TEST YOURSELF

Q: Per 330.24(B), what is the minimum bending radius for interlocked-type armor or corrugated sheath MC cable?

A) 7 times the external diameter
B) 10 times the external diameter
C) 12 times the external diameter
D) 15 times the external diameter

(Comment your answer 👇)

FOLLOW — Part 3 wraps up ampacity and construction specs ⚡ #JoshTheSparky #NEC2026 #ElectricianLife

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