Quick Hits

EPISODE 6 — Construction Specs: Armor, Conductors, Grounding & Marking — Article 320 FINALE (320.100–320.120)

Slide 1 — Hook "Final episode of Article 320! How Type AC cable is actually built — and why that internal bonding strip matters more than people realize."

Slide 2 — 320.100 & 320.104

• 320.100 Construction: Type AC has a flexible metal tape armor, PLUS an internal bonding strip (copper or aluminum) in intimate contact with the armor along its ENTIRE length. That bonding strip's job is to reduce the spiral armor's inductive reactance and make the armor more effective as an equipment ground — it's NOT required to connect to an EGC terminal, and can simply be cut off or bent back at termination.

• 320.104 Conductors: insulated conductors must be a type listed in Table 310.4(1) (or otherwise identified for use in this cable), PLUS have an overall moisture-resistant, fire-retardant fibrous covering. Type ACT specifically only needs that moisture-resistant fibrous covering on the INDIVIDUAL conductors, not overall.

Slide 3 — 320.108 & 320.120

• 320.108 Equipment grounding conductor: Type AC's armor itself has to provide an adequate fault-current path per 250.4(A)(5)/(B)(4) — meaning the armor (helped by that bonding strip) functions as the cable's EGC.

• 320.120 Marking: follows 310.8's general marking rules, PLUS Type AC specifically needs the manufacturer readily identifiable via distinctive external markings on the cable armor itself, running its ENTIRE length.

Slide 4 — Quiz + CTA Q: "Does Type AC cable's internal bonding strip need to be connected to an equipment grounding terminal at termination?" A) Yes, always required B) No — it can be cut off or bent back at termination C) Only in wet locations D) Only for conductors 6 AWG and larger

✅ Answer: B — 320.100: the bonding strip's purpose is to help the armor function as an EGC path; it isn't itself required to connect to a grounding terminal.

CTA: 🎉 That's a wrap on ALL of Article 320 — Armored Cable, Type AC! Follow for more daily quick-hit study notes as we move into Article 322 (Flat Cable Assemblies: Type FC) next.

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