Code Change Summary: Revised and relocated language clarifies the permitted conductor materials for wiring device terminations and eliminates previous confusion about CO/ALR marking requirements.

SME commentary: In the 2026 NEC^®, the former Section 406.3(D) covering Receptacle Terminations has been reworded, clarified, and relocated to new Section 406.10 titled Wiring Device Terminations. The previous text created confusion due to its reverse phrasing which led to misinterpretation about the compatibility of aluminum, copper, and copper-clad aluminum conductors with device terminals. The revised section now uses clearer, positive language and broadens applicability to all wiring devices, not just receptacles.

The 2023 NEC^® language stated that receptacles not marked “CO/ALR” could only be used with copper and copper-clad aluminum conductors, while devices marked “CO/ALR” could be used with aluminum, copper, and copper-clad aluminum. That structure caused misapplication in the field, where some installers incorrectly assumed copper and copper-clad aluminum conductors were interchangeable and that the rule’s intent was to treat copper and copper-clad aluminum conductors as equal. The true purpose of the section has always been to restrict the use of aluminum conductors unless the device is specifically listed and marked “CO/ALR.”

The 2026 revision corrects this by re-organizing the requirements under two simple provisions. First, wiring devices marked CO/ALR are permitted to directly terminate aluminum, copper, or copper-clad aluminum conductors when used in accordance with the branch-circuit conductor size and type identified by the manufacturer’s instructions. Second, wiring devices not marked CO/ALR are prohibited from directly terminating aluminum conductors but may terminate copper or copper-clad aluminum conductors if permitted by the manufacturer. This structure presents the requirements in logical order, beginning with the allowances for devices bearing the CO/ALR marking, followed by the limitations for those without it.

These revisions also acknowledge current industry practice. Most device manufacturers clearly identify acceptable conductor materials on the device body or packaging. Some devices are marked for copper only and cannot be used with aluminum or copper-clad aluminum, while others are listed for copper and copper-clad aluminum.

The Committee Statement for the change emphasized that the revisions were not intended to alter performance or listing requirements but to prevent misunderstanding in the field and to ensure safe use of aluminum conductors. The updated language ensures that any termination must follow the device’s listing, manufacturer markings, and installation instructions, which are key elements in maintaining Code compliance and product integrity.

By expanding the rule to cover all wiring devices, including receptacles and switches, and by employing precise, positive wording, Section 406.10 intends to provide the installer and inspector with a straightforward reference for determining allowable terminations. The relocation also positions these requirements logically within the reorganized Article 406, which now governs all wiring devices under a unified structure. The result is clearer Code language, improved usability, and stronger alignment between NEC^® requirements and the proper use of manufactured products.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2026 NEC^® edition of NFPA 70.

2023 Code Language:

406.3(D) Receptacle Terminations. Receptacle terminations shall be in accordance with the following:

(1) Terminals of 15- and 20-ampere receptacles not marked CO/ALR shall be used with copper and copper-clad aluminum conductors only.

(2) Terminals marked CO/ALR shall be permitted to be used with aluminum, copper, and copper-clad aluminum conductors.

2026 Code Language:

406.10 Wiring Device Terminations. Wiring device terminations shall comply with all of the following:

(1) Wiring devices marked CO/ALR shall be permitted to directly terminate aluminum, copper, or copper-clad aluminum conductors in accordance with the branch-circuit conductor size (AWG) identified by the manufacturer’s instructions.

(2) For wiring devices not marked CO/ALR, both of the following shall apply:

a. They shall not be permitted to directly terminate aluminum conductors.

b. They shall be permitted to directly terminate copper conductors, copper-clad aluminum conductors, or both in accordance with the branch-circuit conductor size (AWG) and type of conductors identified by the manufacturer’s instructions.