Electrical contractors need to choose the right wire type for each project. In commercial and industrial applications, both XHHW-2 (cross-linked polyethylene High Heat-resistant Water-resistant) and THHN (Thermoplastic High Heat-resistant Nylon-coated) are a popular choice of building wire. Most THHN building wire comes with the dual rating THHN/THWN, meaning it is usable in both wet and dry conditions, as well as both indoor and outdoor use. XHHW-2 can also be used in wet or dry indoor and outdoor applications. Both wires are also available with copper or aluminum conductors in stranded or solid and have a voltage rating of 600V. Because of the similar functional properties, it can be difficult to choose between the two.
The following are distinctions between THHN and XHHW-2:
A major difference between XHHW-2 and THHN is the materials that each wire is made up of. THHN wire is designed with a PVC (polyvinyl chloride) insulated nylon sheath. The hygroscopic nylon jacket absorbs moisture and is more susceptible to damage in wet environments. The UL rating for THHN is 90 degrees Celsius in dry environments and 75 degrees Celsius in wet environments.
XHHW-2, is made up of XLPE (cross-linked polyethylene) which provides a dielectric constant (k) value usually ranging from 2.2 to 3.0 megohms @ 20° C, allowing XHHW-2 to resist leakage at higher temperatures. The UL rating for XHHW-2 is 90 degrees Celsius in both wet and dry locations. This makes XHHW-2 a safer choice for applications in wet environments.
XHHW-2 and THHN also contain differences in jackets. The jacket of THHN is thin, which makes it easier to maneuver through underground conduit. THHN has relatively thin PVC insulation which improves conductivity but reduces the flexibility of the wire. However, flexibility and safety can be improved using cable bundles.
XHHW-2’s thermoset material gives it great flexibility, making it suitable for applications that may involve bends or sharp corners. Additionally, because the jacket of XHHW-2 is much thicker, it is more protected from chemical damage such as abrasions or leakage.
THHN is a popular choice for electrical contractors because of its ability to meet the requirements of electrical applications at a low price point. Its affordability often makes it a better alternative to XHHW-2. XHHW-2’s thermoset insulation and high temperature resistance make it a more expensive option. Despite XHHW’s performance benefits such as increased protection and higher flexibility, THHN is still very well suited for commercial and industrial applications Choosing between the two will depend on the specificities of the installation.
Which wire is best for a construction project will depend on the type of application and its budget. Both THHN and XHHW-2 are commodity building wires. While they carry some distinct differences in material composition and cost, both are up to the NEC® (National Electric Code®) standard for the safe installation of electrical wiring and equipment in the United States. Kris-tech can also customize both XHHW-2 and THHN by color for the specificities of the project.
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