Spot the Violation

ElectricalTerminations, splices & conductorsLevel 22023 NEC

Replaced receptacle in a 1972 split-level

Wood-paneled bedroom wall near the floor with orange shag carpet. A new white tamper-resistant duplex receptacle is pulled out of a gray metal device box. A gray NM cable printed 12-2 AL enters the top of the box; its black and white conductors have silver-colored stripped ends looped under the receptacle's side screws, and a bare silver grounding conductor wraps the box ground screw and continues to the receptacle's green screw. The receptacle's mounting strap is stamped 15A 125V and CU / CU-CLAD ONLY. A brown plastic cover plate and a screwdriver lie on the carpet. 12-2 AL 15A 125V CU / CU-CLAD ONLY TR
Bedroom receptacle swapped by the homeowner, 1972 split-level

What's wrong here?

  1. Aluminum conductors are landed on a receptacle not marked CO/ALR
  2. Aluminum branch-circuit wiring is no longer permitted and must be rewired
  3. Any receptacle on an aluminum circuit must be GFCI protected
  4. Nothing. This installation is compliant
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Show the answer and the code reference

The answer

Solid aluminum branch-circuit conductors are wrapped directly under the screws of a receptacle marked for copper and copper-clad wire only, not CO/ALR.

Correct choice: 1. Aluminum conductors are landed on a receptacle not marked CO/ALR

Aluminum creeps and grows a high-resistance oxide, so a screw terminal made for copper can loosen and overheat on aluminum wire. Under 406.3(D)(1), the terminals on a 15 A or 20 A receptacle not marked CO/ALR are for copper and copper-clad aluminum only, and a receptacle meant for direct aluminum connection must be marked CO/ALR (406.3(C)). That is the receptacle version of the general rule in 110.14 that terminals be identified for the conductor material, and landing aluminum on a strap stamped CU / CU-CLAD ONLY also breaks the listing (110.3(B)). Homes built from about 1965 to 1973 may have solid aluminum branch circuits, and device swaps like this one are where overheated connections start.

How to fix it

Replace it with a receptacle marked CO/ALR (tamper-resistant, as 406.4(D)(5) and 406.12 require here), or splice short copper pigtails onto the aluminum conductors with connectors listed for aluminum-to-copper connections and land the copper on a standard device. Because this is a replacement in a bedroom, also provide the AFCI protection that 406.4(D)(4) requires.

Code references

  • NEC 2023 406.3(D)(1) — Receptacle Terminations

    Terminals of 15 A and 20 A receptacles that are not marked CO/ALR may be used only with copper and copper-clad aluminum conductors. Terminals marked CO/ALR may be used with aluminum, copper, or copper-clad aluminum.

    Drills citing 406.3(D)(1)

  • NEC 2023 110.14 — Electrical Connections

    Because dissimilar metals behave differently, pressure terminals, pressure splicing connectors, and soldering lugs must be identified for the material of the conductor and properly installed and used. Dissimilar metals may not be intermixed in a terminal or splicing connector where they contact each other unless the device is identified for that purpose.

    Drills citing 110.14

  • NEC 2023 406.3(C) — CO/ALR Receptacles

    Receptacles rated 20 A or less that are designed for direct connection of aluminum conductors must be marked CO/ALR.

    Drills citing 406.3(C)

  • NEC 2023 110.3(B) — Installation and Use

    Listed or labeled equipment must be installed and used according to any instructions included in the listing or labeling.

    Drills citing 110.3(B)

2026 NEC:renumbered to 406.10. The 2026 NEC moved the receptacle-termination rule from 406.3(D) into new 406.10 Wiring Device Terminations (Article 406 now also covers device-type switches) and reworded it: devices not marked CO/ALR may not directly terminate aluminum. The answer is unchanged; the exact 406.10 subdivision was not confirmed. Confidence: medium

Minnesota

MN adopts the NEC rule as writtenConfidence: high

Minnesota adopted the 2023 NEC without amendment as the Minnesota Electrical Code (Minn. Rules 1315.0200; Minn. Stat. 326B.35), effective July 1, 2023, so 406.3, 406.4, and 110.14 apply as published. That edition governs permits filed through Aug. 16, 2026; permits filed on or after Aug. 17, 2026 fall under the 2026 NEC; see the 2026 NEC note on this drill for how the cited section fares there. Whether a device replacement needs a permit is a separate Minnesota licensing and inspection question, not answered by this drill.

How Minnesota adopts the NEC

Why the other choices are wrong

  • Aluminum branch-circuit wiring is no longer permitted and must be rewired. Existing aluminum branch-circuit wiring may stay. The Code issue is the termination: it needs a CO/ALR device or listed Al/Cu connectors and copper pigtails (406.3(D), 110.14).
  • Any receptacle on an aluminum circuit must be GFCI protected. GFCI requirements in 210.8 are based on location, not conductor material. The fix for aluminum is a terminal identified for aluminum.
  • Nothing. This installation is compliant. The silver conductors are aluminum (the sheath reads 12-2 AL), and this device is stamped for copper and copper-clad wire only. 406.3(D)(1) limits terminals not marked CO/ALR to copper and copper-clad aluminum.
Safety hazardLevel 2 · Journeyman#aluminum#receptacle#co-alr#termination#older-home

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