UL Type Use-2 Rhh Rhw-2 Cable Wire

UL Type Use-2/RHH/RHW-2 Rated 600V Cable Wire
Let's explain what USE-2, RHH/RHW-2 means:
RHH
While RHH wires do not play well with moisture, they can sustain higher temperatures than RHW-2 wires. They hold a 600 voltage rating.This doesn't mean one cable is better than the other or vice-versa; it simply means that each cable is specifically designed to work in different locations.

If a cable is rated as USE or USE-2, that means it is approved as a direct burial cable or an underground service entrance cable. RHW-2 and RHH wires are commonly USE-2 rated because of their properties and benefits. RHW-2 wires are suitable for direct burial in both wet and dry locations. Along with RHH cables, they hold a 600 voltage rating.

Photovoltaic Industry:  USE-2 wires are often used in the photovoltaic industry because of their direct burial benefits, as well as their resistance to flame, heat, moisture, and sunlight. The ability to be used both above and below ground is extremely important, especially when dealing with photovoltaic applications that present high temperatures, UV radiation, and sunlight exposure. The introduction of USE-2 wires will continue to grow as renewable green energy grows in importance.

RHW-2 wire is useful in environments where it is susceptible to moisture, dampness, and other possible water encounters. 

The "W" label even suggests that the cables can be submerged in water if needed. Even if the wire has "R," which means it is acceptable to use in damp locations, it is wise to keep these wires away from water if the "W" isn't present. Wires without this "W" label are susceptible to failure and erosion when exposed to water and other liquids.