NEC 2023 Section 406.3 Receptacle Terminations

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1. Receptacles with Standard Terminals (15 and 20 Ampere):
   • This clause specifies that standard terminals on 15-ampere and 20-ampere receptacles, not marked CO/ALR, should be used only with copper or copper-clad aluminum conductors. It implies that these receptacles are not suitable for pure aluminum conductors, likely due to concerns about the physical and electrical properties of aluminum compared to copper.
2. CO/ALR Marked Terminals:
   • Terminals that are marked CO/ALR are more versatile. They can be used with aluminum, copper, and copper-clad aluminum conductors. CO/ALR stands for Copper/Aluminum Revised, indicating these terminals are designed to accommodate the different properties of these conductors, especially important due to the historical issues with aluminum wiring in the past.
3. Screwless Terminals (Push-in Type) for 15-Ampere Circuits:
   • Receptacles that use screwless, push-in terminals (also known as push-in-terminals) are restricted to 15-ampere branch circuits. They must be connected with 14 AWG solid copper wire only unless they are specifically listed and marked for use with other conductor types. This restriction is likely due to the limitations in the securement and conductivity properties of these types of terminals.

The informational note directs to UL 498, a standard for Attachment Plugs and Receptacles, for more details about screwless terminals. It clarifies that different types of screwless terminals, like the separable-terminal assembly, spring-action clamp, and insulation-displacement types, are not classified under the same category as push-in terminals in UL 498.

These guidelines reflect careful consideration of safety and compatibility in electrical installations, ensuring that receptacles are used in a manner consistent with their design and the properties of the conductors they connect to.