Armored vs Non-Armored Cables Guide

Posted on Friday Jan 03, 2025 at 06:32PM in Educational Resources

When to Use Armored Cables vs Non-Armored Cables

Updated: August 18, 2025

TL;DR: Use armored cable (AC or MC) when conductors are exposed or likely to take abuse, in commercial and industrial spaces, above ceilings, in plenums or risers if listed, and in many healthcare or assembly areas. Use non-armored cable like NM-B only in dry, protected interiors where the code allows it, or use individual conductors in raceway. Underground or wet locations call for wiring methods actually listed for wet conditions, such as PVC-jacketed MC or UF-B. Start with the environment and the code article, then pick the wiring method and fittings. Keep one Revco category handy early in the takeoff, like the Wire, Cord & Cable assortment, so you can match cable families and fittings as you plan.

Why this matters on the job

Cable choice decides how fast you rough-in, how clean the inspection goes, and how well the installation holds up when facilities staff start banging carts down the corridor. Armored cable gives you mechanical protection out of the box and often satisfies grounding paths with the right construction and connectors. Non-armored cable can be faster in wood framing and lower-risk interiors, but only where the code allows. The wrong call leads to red tags or, worse, damage later. Stocking from a reliable local source like Revco’s Non-Metallic Sheathed Cables and Armored Wires & Cables families keeps projects moving in Suffolk County and nearby.

Fundamentals

There are two big buckets here:

Armored cable
- Type AC (Article 320) uses interlocked metal armor and a bonding strip. It can serve as the equipment grounding path when installed with listed fittings in accordance with 250.118(10) and Article 320. Electrical License RenewalAmerican Legal Publishing
- Type MC (Article 330) encloses conductors in an interlocked or smooth/corrugated metal sheath. Many MC constructions are available, and some are listed for wet locations. Electrical License Renewal
- Use listed fittings, size and support correctly, and follow manufacturer instructions. Anti-short bushings are required at AC terminations unless the fitting provides equivalent protection; they are not an NEC requirement for MC when listed fittings are used. mikeholt.comNEMA
Non-armored cable
- Type NM-B (Article 334) is for dry interior locations. It is common in one- and two-family dwellings and permitted in certain other building types with limitations. It is not permitted in wet or damp locations. Electrical License Renewal+1
- UF-B (Article 340) is for direct burial and wet locations. Use UF-B where you need underground branch circuits without raceway. Confirm cover per Table 300.5. Electrical License Renewal

For quick category sourcing while you plan, use Revco’s Wire, Cord & Cable hub and drill into Steel armor copper conductors or Aluminum armor copper conductors.

Code and compliance

Physical damage risk
Where subject to physical damage, protect conductors, raceways, and cables. This drives armored selections in exposed areas and informs nail-plate protection rules when you do use NM. See 300.4 and the AC/MC framing rules in 320.17/330.17. ICC Digital Codesmikeholt.com
Location type
- Dry only: AC cable and NM-B are dry-location products. AC cannot go in damp or wet locations, including underground raceways that are defined as wet. Default
- Wet or corrosive: Use MC specifically listed for wet locations, often with a PVC jacket and wet-rated insulation (for example, THWN-2), or use a raceway method with wet-rated conductors. UF-B is an option for direct burial. Verify listing marks. Electrical License Renewal
Underground
Underground wiring methods must meet Table 300.5(A) minimum cover. The inside of underground raceways is a wet location, which rules out NM-B in those raceways. Electrical License RenewalEC&M Magazine
Support, securement, fittings
AC and MC need listed connectors and correct securing/spacing. AC requires an insulating bushing at terminations unless the fitting provides equivalent protection (320.40). MC requires listed fittings; anti-shorts are optional unless the fitting or manufacturer says otherwise. mikeholt.com

For fittings and transitions, keep compatible hardware on hand from Revco’s Conduit & Conduit Fittings aisle, and select listed conduit connectors or liquid-tight connectors that match the cable armor and jacket.

Selection steps

Step 1: Identify the environment.
Is the run exposed and likely to be bumped or abraded? If yes, lean armored. If the area is dry, protected, and residential framing, NM-B may be fine. In wet, corrosive, or underground settings, pivot to wet-listed MC with PVC jacket or UF-B. Check Article 300 general rules and the product listing. NFPA

Step 2: Match the code article to the environment.

Dry, exposed commercial ceiling: AC or MC.
Healthcare or assembly areas: MC constructions as allowed by Articles 330 and 517, as specified.
Residential stud bays: NM-B per 334, protected at 1-1/4 inch from nailing surfaces or with plates. mikeholt.com

Step 3: Verify listing and markings.
Look for “Type AC” per UL 4 or “Type MC” per UL 1569 on the jacket or reel. Wet locations require the wet-location identification and often a PVC jacket. Shop UL Standards+1

Step 4: Size conductors and overcurrent per 310.16, 110.14(C), and 240.4(D).
Use conductor ampacity from Table 310.16 and stay within device termination ratings. The small conductor rules limit 14 AWG copper to 15 A, 12 AWG to 20 A, and 10 AWG to 30 A. Verify conditions of use if you bundle or derate. cabletechsupport.southwire.com

Step 5: Choose fittings for the armor and jacket.
Use listed MC/AC connectors sized to cable OD. Where you transition to raceway, pick compatible conduit connectors. For wet locations, use listed liquid-tight connectors. NEMA guidance: match fitting clamp range to the actual cable diameter, not just the AWG count. NEMA

Step 6: Plan support and protection.
Respect the article-specified distances and add protection where you cross surfaces within reach. Guard strips or plates protect where cables cross framing surfaces within 7 feet of the floor or similar locations. Electrical License Renewal

While building your takeoff, tag likely picks in Revco’s steel armor copper MC or PVC-jacketed MC shelves so procurement can release material on schedule.

Sizing or configuration examples

Example A: Dry, exposed corridor, 120 V, 20 A branch circuit

Environment: Exposed routing above accessible ceiling in a commercial corridor.
Wiring method: Type MC with copper THHN/THWN-2.
Conductor size: 12 AWG copper at 20 A per 240.4(D).
Fittings: Listed MC connectors sized to OD.
Why armored: Physical damage risk and easier support above ceiling.
Check Revco’s steel armor copper MC family for 12/2 or 12/3.

Example B: Residential bedroom circuit, wood framing

Environment: Dry, concealed in studs.
Wiring method: NM-B.
Conductor size: 14 AWG copper at 15 A or 12 AWG at 20 A.
Protection: Maintain 1-1/4 inch clearance or add steel nail plates.
Shop Revco’s NM-B selection.

Example C: Outdoor shed feeder with trench

Environment: Underground run to outbuilding.
Wiring method: UF-B direct burial at required cover per Table 300.5, or PVC conduit with wet-rated conductors or wet-listed MC.
Note: Underground raceway interiors are wet locations. NM-B is not permitted there. Electrical License RenewalEC&M Magazine
Select fittings from Revco’s Conduit & Fittings.

Installation and wiring notes

Cut and prep correctly. Use the right rotary armor tool, maintain jacket integrity, and follow manufacturer strip lengths. AFC and Southwire publish step-by-step instructions for MC terminations; AC terminations require the insulating bushing or equivalent protection per 320.40. dam.atkore.compimmedia.winsupplyinc.com
Grounding and bonding. AC’s bonding strip with listed fittings completes the fault path when installed per listing. MC may carry a full-size equipment grounding conductor or use the sheath where permitted by 250.118(10), depending on construction and listing. American Legal Publishing+1
Support and secure. Follow article-specific support intervals and add protection where cables cross surfaces within reach. mikeholt.com
Transitions and terminations. For raceway transitions, use combination couplings and bushings where required.
Wet locations. Look for THWN-2 insulation and “wet location” on the MC print legend, often with a PVC outer jacket per the listing. Use liquid-tight connectors with gaskets from Revco’s liquid-tight connector section. Electrical License Renewal

Job-site Lessons:

Do not fish NM-B through exterior conduits to “protect” it; that raceway is a wet location. It will get flagged. EC&M Magazine
Inspectors will look for the anti-short bushing on AC. On MC, they will look for listed connectors, not red heads. Keep the NEMA bulletin handy. NEMA

Testing, commissioning, and documentation

Continuity and insulation checks. Before energizing, meter the equipment grounding path and megger insulation where required by spec.
Labeling. Mark panel schedules and cable types. Note where special MC constructions are used (for example, MC-PCS or PVC-jacketed). NEMA publishes guidance on MC-PCS selection and installation that is useful for documentation packages. NEMA
As-builts. Photograph concealed transitions or areas with added protection plates and include in turnover.

If you need last-minute fittings, Revco carries armored/MC angle connectors and standard conduit connectors.

Troubleshooting

Tripped breaker on a new MC run: Check for jacket damage at connector, missing anti-short on AC, or improper fitting that allows armor to cut insulation. Use listed connectors and proper strip length. dam.atkore.com
Nuisance AFCI trips on NM-B: Inspect staples and bends. Replace crushed sections and re-secure per 334.30 requirements. Electrical License Renewal
Failed insulation resistance in a damp area: Verify the cable is actually listed for wet locations or re-pull with a proper method.

FAQ

Can I run AC cable outdoors if I sleeve it in PVC?
No. AC is not permitted in damp or wet locations. Sleeving it in underground PVC does not change that, and the inside of that raceway is a wet location. Use wet-listed MC with PVC jacket, a raceway with wet-rated conductors, or UF-B as applicable. DefaultElectrical License Renewal

Do I always need anti-short bushings with MC?
No. The NEC does not require anti-short bushings for MC when listed fittings are used; AC terminations require them unless the fitting provides equivalent protection. Some manufacturers include red heads for MC as optional added protection. mikeholt.comNEMA

Where is NM-B allowed in commercial buildings?
Only in specific construction types and conditions, generally concealed in dry locations, and as allowed by 334.10 with the prohibitions in 334.12. Electrical License Renewal+1

Is MC allowed in plenums?
Yes, where the specific MC construction is listed for use in environmental air spaces and installed per 300.22. Verify the cable’s marking. Electrician U

Common mistakes to avoid

Pulling NM-B in outdoor or underground raceways. Not permitted; it is a wet location. EC&M Magazine
Using unlisted fittings on AC/MC or mismatching fitting clamp range to cable OD. Use listed hardware sized to the actual cable diameter. NEMA
Skipping protection plates where cable is within 1-1/4 inch of nailing surfaces. mikeholt.com
Assuming all MC is automatically okay in wet locations. Only listed constructions are. Electrical License Renewal

Parts to stock and related products

Armored cable families: Steel armor copper MC, Aluminum armor copper MC, PVC-jacketed MC.
NM-B for interiors: Non-Metallic Sheathed Cables.
Fittings: Conduit connectors, liquid-tight connectors, combination couplings.
Conduit & raceway: Conduit & Conduit Fittings.

When to call the AHJ or engineer of record

You are mixing power and control conductors in a single MC or planning to use MC-PCS. Confirm the listing, segregation, and terminations with the design team and inspector. NEMA
You are in a damp garage, on a rooftop, or a food prep area and need to confirm “wet location” status and acceptable wiring methods.
You plan to use NM in a building type or space where allowances are tight.

Disclaimer

Always verify requirements with your Authority Having Jurisdiction and the current manufacturer instructions before you order or install.

Credits

Author: Revco Editorial Team — Electrical Content Editor — 15+ years producing contractor-focused guides and product specs.
Technical review: Pending — add approved name/credential — Master Electrician or PE reviewer to be assigned.
Contact: (631) 283-3600

About Revco Lighting & Electrical Supply

Since 1978, Revco Lighting & Electrical Supply has been helping professionals bring their projects to light—literally. As a go-to source for lighting and electrical products across Long Island, NY and nearby areas, we specialize in supporting contractors, builders, and industry experts with practical solutions and dependable service. Whether it’s a complex commercial build or a simple residential upgrade, we’re here to make sure you have what you need, when you need it.

Sources

Armored vs unarmored cables and wires

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