THHN uses thermoplastic PVC insulation with a nylon covering; XHHW-2 typically uses thermoset cross-linked polyethylene (XLPE). THHN alone has a 90°C dry-location rating. A verified THHN/THWN-2 product and XHHW-2 can both carry a 90°C wet-and-dry rating. For buyers comparing THHN vs XHHW, the practical decision involves the complete marking, insulation system, installation route and approved product data.
This guide compares single-conductor building wire. XHHW-2 appears here as a comparison option. KingForYou’s inquiry route on this page is for THHN/THWN-2 specification review, subject to confirmation of the offered construction and certification.
THHN vs XHHW-2 specification differences
The table separates THHN-only wire from dual-rated THHN/THWN-2. Combining them into one column would hide the wet-location distinction.
| Specification | THHN designation alone | Verified THHN/THWN-2 | XHHW-2 |
|---|---|---|---|
| Typical insulation system | PVC insulation with nylon covering | PVC insulation with nylon covering | XLPE thermoset insulation |
| Product standard family | UL 83, thermoplastic-insulated wires and cables | UL 83 | UL 44, thermoset-insulated wires and cables |
| Dry-location conductor temperature | 90°C | 90°C | 90°C |
| Wet-location conductor temperature | No wet rating from THHN alone | 90°C under the THWN-2 designation | 90°C |
| Voltage | Verify the marked product rating | Southwire SPEC 10000 example: 600V | Southwire SPEC 10005 example: 600V or 1000V; verify the ordered product |
| Outer diameter and insulation thickness | Depend on size and construction | Use the selected size’s dimensional data | Use the selected size’s dimensional data |
| Bending and pulling | Product-specific limits | Product-specific limits | Product-specific limits |
| Additional environmental approvals | Check the listing and markings | Check the listing and markings | Check the listing and markings |
Sources: UL Solutions’ Wire and Cable Application Guide, Southwire THHN/THWN-2 SPEC 10000, and Southwire XHHW-2 SPEC 10005. Manufacturer examples are reference products, not KingForYou specifications.
A specification calling for XHHW should be clarified before ordering XHHW-2 or another type. Keep the full designation on the purchase order.
PVC vs XLPE building wire: what the material changes
THHN/THWN-2 combines PVC electrical insulation with a nylon outer covering. XHHW-2 uses a cross-linked insulation system, commonly XLPE. The nylon layer forms part of the THHN construction and should not be treated as optional.
PVC is thermoplastic. XLPE is thermoset: cross-linking changes how the material responds to heat, so it does not remelt like a thermoplastic. This material distinction does not authorize operation above the finished wire’s rated temperature.
Service Wire’s technical comparison discusses these insulation differences and the potential handling advantages of thermoset products. Buyers should still compare the exact constructions. A material-family description cannot establish every finished wire’s chemical resistance, bend behavior or service life.
For compound selection and the distinction between material data and finished-wire approval, see our PVC cable compound guide.
Wet locations and temperature: compare the complete marking
An underground conduit route requires wet-location conductors under the applicable installation rules. Enclosing wire in conduit does not by itself turn that route into a dry location. The ICC wiring-method provisions describe this boundary; the project must follow its locally adopted code.
For this comparison, the useful distinction is:
- A THHN-only designation does not establish wet-location suitability.
- A verified THHN/THWN-2 conductor carries its wet rating through THWN-2.
- XHHW-2 carries a wet-and-dry temperature designation.
If a seller calls a reel “THHN,” request the complete print legend and matching documentation. The shorthand name does not establish a dual rating.
Our THHN vs THWN-2 guide explains those designation differences in detail.
Insulation temperature is not the circuit’s allowable current
A 90°C insulation rating does not automatically permit sizing a circuit from the 90°C ampacity column. Termination limits, ambient conditions, conductor grouping, installation method and applicable circuit rules still govern the calculation.
Do not assume that replacing THHN/THWN-2 with XHHW-2 increases allowable current. Ask the designer to compare both candidates using the same conductor material, size, route and termination conditions. The Southwire installation guide provides engineering references for these checks.
Voltage ratings belong to the specified product
Southwire’s cited THHN/THWN-2 data sheet states 600V. Its cited XHHW-2 data sheet states 600V or 1000V. These examples show why a comparison should identify a manufacturer and product specification alongside a voltage value.
A purchaser should record the voltage required by the design and obtain the corresponding product marking and certification. Do not extend a higher rating from one XHHW-2 product to every product carrying that type name.
If the project specification instead uses an IEC cable designation, review the construction and approval separately. Our low-voltage power cable guide helps distinguish those product families.
THHN or XHHW for conduit: bending and pulling
Conduit selection needs more than a statement that one insulation is “more flexible.”
For the proposed products, ask the installer to check actual outside diameter, conductor construction, bend limits, pulling tension and sidewall pressure. Conduit fill and pull feasibility are separate checks: fitting within the permitted fill does not establish that the planned pull is acceptable.
Keep copper-to-copper comparisons separate from copper-to-aluminium substitutions. Also identify whether the conductor is solid, conventionally stranded or compacted. Changing those variables can affect handling and dimensions alongside the insulation choice.
Southwire’s cable installation references cover pulling tension and sidewall pressure. Use the limits applicable to the selected wire and pulling method.
Lubricant instructions are product-specific too. Southwire identifies its cited SIMpull THHN/THWN-2 product as designed for installation without pulling lubricant. That feature should not be transferred to an unrelated THHN product.
For difficult routes, request an installation review before approving a substitution. A supplier’s sample can help assess stripping and handling, but it cannot replace the pull calculation.
Scenario selection table
The following is a procurement decision aid. Final acceptance depends on the project specification, product listing and approved installation.
| Project situation | Candidate to evaluate | What must be checked |
|---|---|---|
| Indoor dry conduit with a specification allowing thermoplastic building wire | THHN/THWN-2 | Required conductor construction, dimensions, voltage and approval |
| Wet or underground conduit | Verified THHN/THWN-2 or XHHW-2 | Wet rating, approved raceway system and project acceptance |
| Specification explicitly requires XLPE or UL 44 XHHW-2 | XHHW-2 | Match the specified construction; obtain approval before proposing THHN/THWN-2 |
| Existing conduit with limited space | Compare actual offered products | Outside diameter, fill and pull feasibility |
| Long pulls or several bends | Compare actual offered products | Tension, sidewall pressure, bend limits and manufacturer instructions |
| Cold installation conditions | Product with documented installation limits | Minimum installation temperature and relevant handling instructions |
| Oil, chemicals or sunlight exposure | Product with documented suitability for the exposure | Exact substance or exposure, listing and applicable test evidence |
| Direct soil contact | Specifically approved direct-burial construction | Neither type name alone establishes the required approval |
| Purchase focused on KingForYou’s thermoplastic building wire | THHN/THWN-2 inquiry | Written confirmation of the exact offered designation and documents |
Environmental claims need separate evidence
Wet-location suitability, sunlight resistance, oil resistance and direct-burial suitability are different checks in the UL application guide. Do not combine them into a general “outdoor suitable” claim.
For chemical exposure, identify the chemical and service conditions in the RFQ. For a smoke or halogen requirement, name the required test and acceptance criteria rather than using “XLPE” as proof of compliance. If the project includes a drive-fed motor circuit, submit the drive manufacturer’s cable requirements for review as well.
This approach lets the supplier respond to an actual requirement instead of a broad request for “better insulation.”
How buyers should compare quotations
Ask suppliers to quote against the same schedule. Otherwise, a price difference may reflect conductor material, stranding, packaging or certification scope rather than the PVC-versus-XLPE choice.
Include:
- Destination market, applicable installation code and project specification.
- Exact type designation and required product standard.
- Conductor material, size and stranding.
- Required voltage and wet/dry temperature rating.
- Installation route and environmental exposures.
- Colors, quantity by size, reel lengths and delivery requirements.
- Required print legend, identification and traceability.
- Product data sheet, certification details and agreed inspection records.
Review documentation in sequence. First match the data sheet to the quotation. Then verify that the certification covers the offered manufacturer and construction. Finally, compare the sample marking and shipment records with the approved order.
A batch test report and a certificate of conformity have different purposes from a product listing. Request the documents your project requires and keep them tied to the offered wire. Our UL 83 THHN/THWN-2 buyer guide covers certification and inspection checks.
Request a THHN/THWN-2 specification review from KingForYou
For this page, KingForYou’s inquiry focus is THHN/THWN-2. XHHW-2 is included for comparison and is not presented as a KingForYou supply offering.
You can review the current THHN/THWN building-wire product page. Its published designation is THHN/THWN; buyers requiring THWN-2 should request written confirmation of that specific rating and the supporting documents.
Send the following request through the KingForYou contact page:
Please review our THHN/THWN-2 building-wire requirement for [destination market/project].
Required conductor: [material, size and stranding].
Required voltage and temperature rating: [project requirement].
Installation: [route and environment].
Colors and quantities: [schedule].
Packaging: [reel lengths and labels].
Please confirm the exact offered designation, applicable certification, data sheet, sample marking, inspection documents and delivery terms. Identify any deviations before quoting.
