Quick Hits

📱 EPISODE 1 — Article 332 (Part 1 of 2)

Type MI Cable — Scope, Uses & Bending Rules

SLIDE 1 — What Is Type MI Cable?
🔥 THE FIRE-RESISTANT HEAVYWEIGHT

Type MI cable = one or more solid conductors, insulated with highly compressed magnesium oxide, enclosed in a continuous copper or alloy steel (like stainless steel) sheath — with or without a nonmetallic jacket.

Rated 300V or 600V, available 16 AWG and larger with 1–7 conductors per cable (18 AWG+ for two-conductor cables). This is about as tough and heat-resistant as cable gets — commonly used where fire rating and durability really matter.

📋 Listing (332.2): the cable itself, plus staples/hangers, AND fittings for connecting to boxes/cabinets — ALL must be listed and identified.

SLIDE 2 — Uses Permitted (332.10)
✅ MI CABLE GOES ALMOST ANYWHERE

✅ Services, feeders, branch circuits
✅ Power, lighting, control, signal circuits
✅ Dry, wet, OR continuously moist locations
✅ Indoors or outdoors
✅ Exposed or concealed
✅ Embedded in plaster, concrete, fill, or masonry (above or below grade)
✅ Hazardous locations (where other articles specifically permit)
✅ Exposed to oil and gasoline
✅ Exposed to corrosive conditions that don't deteriorate the sheath
✅ Underground (with proper protection from physical damage/corrosion)
✅ In or attached to cable tray

This is one of the most rugged, versatile cables in the Code — moisture, oil, corrosion, extreme locations — MI handles it.

SLIDE 3 — Uses NOT Permitted & Framing Protection
🚫 USES NOT PERMITTED (332.12)

❌ Underground runs UNLESS protected from physical damage where necessary
❌ Conditions destructive/corrosive to the metallic sheath UNLESS additional protection is provided

📍 THROUGH/PARALLEL TO FRAMING MEMBERS (332.17)
Must be protected per 300.6 — same general framing protection rule you'll see across multiple cable articles.

SLIDE 4 — Bending Radius + Exam Question
📐 BENDING RADIUS (332.24)

Simpler than MC cable — just two tiers based on sheath diameter:
🔹 ≤¾ in. (19mm) diameter → 5x the sheath diameter
🔹 >¾ in. to 1 in. (25mm) diameter → 10x the sheath diameter

The point: prevent cracking of the conductor insulation or sheath, which could create a hot spot or moisture entry point.

🧠 TEST YOURSELF

Q: Per 332.24(1), what is the minimum bending radius for Type MI cable not more than ¾ in. (19mm) in external diameter?

A) 5 times the external diameter
B) 7 times the external diameter
C) 10 times the external diameter
D) 12 times the external diameter

(Drop your answer 👇)

FOLLOW — Part 2 wraps up securing, fittings, ampacity, and construction specs ⚡ #JoshTheSparky #NEC2026 #ElectricianLife

← View Chapter 3 Home

← Back To Article 330 Home

← Back To Quick Hits Home