8/3 UF-B x 20′ Southwire Underground Feeder Cable 8/3 UF-B x 20' Southwire Underground Feeder Electrical Wire. Conductor Insulation is 90 °c Rated Polyvinyl Chloride (PVC). 1 x #10 AWG Non-Insulated (Bare) Solid Copper Ground Wire. National Electrical Code (NEC), NFPA 70. byJuly 5, 2026