8 AWG XHHW-2 Stranded Copper Building Wire

XHHW-2 is single-conductor building wire with cross-linked polyethylene (XLPE) insulation, which is where the "X" in its name comes from. "HHW" stands for high heat and water resistance, and "-2" means it's rated 90°C in wet locations as well as dry. 8 AWG copper XHHW-2 is installed in conduit or other NEC-recognized raceways at up to 600V and is rated 50A at 75°C. It's used for 40A and 50A circuits for ranges and wall ovens, 50A circuits for 40A EV chargers, heat pumps, and residential PV inverter output.

Both use cross-linked polyethylene (XLPE) insulation and are rated 600V. The difference is the wet rating. XHHW is rated 90°C in dry locations but only 75°C in wet locations. XHHW-2 is rated 90°C in both, and it passes stricter UL 44 moisture testing. XHHW-2 can be used anywhere XHHW is allowed.

Both THHN/THWN-2 and XHHW-2 are 600V building wires rated 90°C in wet and dry locations, so the real difference is the insulation. THHN/THWN-2 has thin PVC insulation with a nylon jacket. XHHW-2 has a single, thicker layer of cross-linked polyethylene (XLPE), a thermoset material that doesn't melt. XHHW-2 holds up better to abrasion, moisture, and cold. THHN/THWN-2 has a smaller diameter, so more conductors fit in the same conduit, and it usually costs less.

Not directly. XHHW-2 is not rated for direct burial, so it can't go in a trench without conduit. It can be installed underground inside conduit, because underground raceways are wet locations and XHHW-2 is rated 90°C wet. For burial without conduit, use a direct burial cable such as USE-2 or URD.

Yes, in standard building installations. XHHW-2 is a single-conductor building wire meant for conduit or other recognized raceways. It can't be run exposed outdoors or fished through walls like NM cable, so inside a wall it has to be in conduit, such as EMT or flexible metal conduit. The NEC allows a few exceptions, such as cable tray for 1/0 AWG and larger conductors with a CT marking, or open wiring on insulators, but these are uncommon.

Yes. NNC's XHHW-2 is marked sunlight resistant, so it holds up in conduit runs exposed to the sun and where the wire leaves the conduit, such as at a weatherhead. Sunlight resistance doesn't replace the conduit requirement.

Yes. XLPE insulation stays flexible in the cold much better than PVC-insulated THHN, which makes XHHW-2 easier to pull in winter. It's commonly rated for installation down to -40°C (-40°F). Check the spec sheet for the exact minimum.

Yes, for the parts of a solar system that run in conduit. XHHW-2 is widely used in PV installations for DC home runs from the array to the inverter and for AC circuits from the inverter to the panel, as long as the system voltage stays within its 600V rating. It doesn't replace PV wire in exposed array wiring between modules, where NEC 690.31 calls for PV wire or USE-2.