What specifications of wire should be used for outdoor distribution boxes

For outdoor distribution boxes, use UF-B cable for direct burial or THWN-2/XHHW-2 wires in conduit, all rated for wet and UV-exposed environments.Direct Burial WiringUF-B (Underground Feeder, Type B) is ideal for outdoor distribution boxes when the wire will be buried directly in the ground without conduit. It features a solid, heavy-duty thermoplastic jacket that protects against moisture, corrosion, UV exposure, and physical damage from soil or pests. UF-B is commonly used for powering exterior fixtures, pumps, and outbuildings, and must be buried at a minimum depth of 24 inches for high-voltage applications .Conduit WiringFor installations where wires are routed through protective conduit, single-conductor wires such as THWN-2 (Thermoplastic Heat and Water-Resistant Nylon-Coated) or XHHW-2 (Cross-Linked High Heat-Resistant Water-Resistant) are recommended. These wires are:Water-resistant, suitable for wet locationsUV-resistant, safe for exposure to sunlightTemperature-resistant, rated up to 90°C in wet and dry conditionsDurable, able to withstand mechanical stress and chemical exposure THWN-2 is commonly used in residential and commercial outdoor conduit systems, while XHHW-2 offers enhanced durability for high-temperature or chemically challenging environments.Insulation ConsiderationsOutdoor wires must have insulation that resists moisture, UV radiation, and temperature extremes. Common materials include:PVC (Polyvinyl Chloride): Flexible and moderately resistant to sunlight and moisturePE (Polyethylene): Excellent moisture resistance and flexibility in cold climatesXLPE (Cross-Linked Polyethylene): Superior thermal stability, chemical resistance, and long-term durability in harsh outdoor conditions SummaryDirect burial without conduit: UF-B cableConduit installation: THWN-2 or XHHW-2 single-conductor wiresInsulation: Choose PVC, PE, or XLPE depending on environmental conditionsEnsure compliance with local electrical codes and NEC requirements for outdoor and wet locations Using these wire types ensures safety, longevity, and reliable performance for outdoor distribution boxes under varying environmental conditions.