What type of wire is suitable for underground installations?

UF (Underground Feeder) cable is specifically designed for direct burial in the ground, making it suitable for underground installations. This type of cable is rated for wet locations and is constructed with a robust, moisture-resistant insulation, allowing it to withstand the environmental conditions typically found underground. UF cable can also be used for various applications, including feeding power to outdoor equipment and installations that require protection from water and soil.

In contrast, Romex cable, while commonly used in residential installations above ground, is not rated for direct burial as it lacks the necessary moisture-resistant features. MC cable, though durable and often used for indoor and outdoor applications, must not be directly buried without additional conduit protection. SJ cable is primarily designed for flexible appliance wiring and is also unsuitable for underground use due to its lack of adequate moisture protection and direct burial rating. Thus, UF cable stands out as the most appropriate choice for underground installations.