What is used to signify that a receptacle is rated for use with aluminum conductors?

The designation used to signify that a receptacle is rated for use with aluminum conductors is indicated by the marking ALR. This representation informs the installer or user that the receptacle has been specifically designed to safely accommodate aluminum wiring, which can have different characteristics compared to copper wiring.

Using aluminum conductors requires specific considerations due to their distinct properties, such as a higher tendency to oxidize and a different thermal expansion rate compared to copper. The ALR marking ensures that users comply with safety standards and manufacturer guidelines; using a receptacle not rated for aluminum conductors could lead to overheating, poor connections, or potentially hazardous conditions.

Other markings, like AL/CU, denote compatibility with both aluminum and copper conductors but might not always specify that the receptacle is rated for use specifically with aluminum. Similarly, CU-AL would typically not indicate that it is rated specifically for aluminum, but rather suggests compatibility between the materials without guaranteeing safety for the particular usage context.