Comparing cable types
THHN vs XHHW-2: which cable do you have?
Both are 600-volt building wire with copper or aluminum conductors, and both are common on Tennessee jobs. The difference is the insulation compound, and it changes where the cable can be installed.
THHN uses thermoplastic insulation with a nylon jacket. XHHW-2 uses cross-linked polyethylene. That single difference drives the wet-location rating, the physical toughness, and how a buyer values the reel.
What the letters mean
THHN is thermoplastic, high heat-resistant, nylon-coated. THWN adds a wet-location rating, and THWN-2 raises the wet rating to 90°C. Most modern THHN is dual-marked THHN/THWN-2, which is why the print often reads both.
XHHW is cross-linked polyethylene, high heat-resistant, water-resistant. The -2 suffix means it is rated 90°C in both dry and wet conditions. XHHW-2 is the version most often specified today for wet, buried and industrial work.
Where each is used
THHN fills conduit in commercial buildings: branch circuits, feeders, panel work. It pulls easily, terminates neatly and comes in the full range of colors. XHHW-2 is specified where moisture, cold or physical abuse is a concern — underground feeders, exterior runs, industrial plants and anything direct-buried where permitted.
| THHN / THWN-2 | XHHW-2 | |
|---|---|---|
| Insulation | PVC thermoplastic with nylon jacket | Cross-linked polyethylene (XLPE) |
| Temperature | 90°C dry, 75°C or 90°C wet depending on marking | 90°C dry and wet |
| Wet locations | Rated when dual-marked THWN-2 | Rated |
| Typical use | Conduit branch circuits and feeders | Wet, buried, exterior and industrial runs |
| Identification | Print reads THHN or THHN/THWN-2 | Print reads XHHW or XHHW-2 |
Questions about this
Is THHN the same as THWN?
No. THWN carries a wet-location rating that plain THHN does not. Most current stock is dual-marked, which is why the print usually shows both.
Which is worth more as surplus?
Value follows the metal, size and condition more than the insulation type, but XHHW-2 in large sizes is often specified for higher-value work.
Can I mix them in one lot?
Yes. List them as separate lines so each is identified correctly.