What type of cable should be used for outdoor electrical installations?

UF (Underground Feeder) cable or weatherproof conduit is the appropriate choice for outdoor electrical installations due to its design and materials, which are specifically intended to withstand outdoor conditions. UF cable is constructed with a moisture-resistant insulation, allowing it to be buried directly in the ground, making it well-suited for outdoor use where exposure to the elements can occur. Additionally, weatherproof conduit offers an extra layer of protection for conductors against moisture, physical damage, and other environmental factors.

In contrast, standard NM (Non-Metallic) cable is not rated for outdoor use and can deteriorate when exposed to moisture and UV light. THHN cable is typically used for dry locations and generally requires protection from the elements, often needing to be run within conduit when used outdoors. While AC (Armored Cable) does provide some physical protection, it is not specifically designed for direct exposure to outdoor environmental conditions without additional protective measures, making it less ideal for outdoor installations compared to UF cable or weatherproof conduit.