How far from the outer surface of a nonmetallic enclosure should a metallic plug or plate be recessed?

The guideline regarding the recessing of metallic plugs or plates is tied to the safety of electrical installations, especially in nonmetallic enclosures. A metallic plug or plate set to be recessed by 1/16 inch from the outer surface of the nonmetallic enclosure minimizes the risk of accidental contact while maintaining a secure fitting. This small distance ensures that the metallic components do not protrude and potentially compromise the seal of the enclosure or lead to unintended exposure that could pose a safety hazard.

Recessing the plug or plate appropriately also helps manage potential issues related to environmental factors, such as moisture and dust, which could affect the performance and safety of the electrical installation. In contrast, greater recessing distances, such as 1/8 inch or beyond, could be excessive and unnecessary for safety and functionality, while smaller values like 1/32 inch may not provide sufficient physical separation. Therefore, the 1/16 inch standard strikes a balance between safety, functionality, and performance in electrical installations.