Insulation Matters: THHN vs XHHW-2, What's Best for Your Project?

THHN/THWN-2 and XHHW-2 are two popular types of cable insulation used for single conductors. THHN/THWN-2 is a thermoplastic product, and XHHW-2 is a thermoset product. Thermosets will harden when exposed to heat and, once they are set and cured, cannot be re-melted or reshaped. Thermoplastics, on the other hand, will soften when heated and can be repeatedly melted and reshaped. They each have strengths and weaknesses that should be considered when specifying cable for a project.

THHN vs XHHW-2: How are They Different?

THHN Insulation — Thermoplastics

THHN/THWN-2 is an acronym for “Thermoplastic—High Heat Resistant—Water Resistant—Nylon Jacket—Temperature Rated 90°C Wet/Dry”.  One advantage of this insulation type is that it is cheaper than thermoset. It is also lighter in weight, making it easier to work with for some applications.  

The plastic in THHN/THWN-2 is PVC, which is more prone to cable failure through current leakage or breakdown from exposure to chemicals or environmental hazards. When PVC is burned it emits a toxic smoke, making it less suitable for enclosed spaces with people, such as offices and transit systems.

Thermoplastic products are temperature rated for 14°F. When exposed to temperatures below this rating, cables can stiffen, crack and break. Using this type of insulation in cold environments can not only destroy the cable, but it can also put everyone near the cable in danger.

XHHW-2 Insulation — Thermosets

XHHW-2 is an acronym for “Cross-Linked Polyethylene (XLPE)—High Heat Resistant—Water Resistant—Temperature Rated 90°C Wet/Dry”. Instead of PVC, these products have XLPE insulation. XLPE provides a number of advantages to XHHW-2 insulation.

XLPE is dual rated 600V/1kV, hospital grade, and it offers better insulation resistance. It provides more protection against chemicals, abrasions and other environmental hazards. This makes it an ideal choice for many commercial and industrial applications. It is also far less toxic than PVC when burned, making it a safer choice for enclosed spaces where people are typically present.

XHHW-2 is more flexible than thermoplastic, therefore it is better able to make tight bends in close spaces. It is also temperature rated for -40°F. This enables it to maintain strength and flexibility in cold weather conditions.

Although it is more expensive up front than thermoplastic, XHHW-2 provides added durability, safety, and longevity — often making it a less expensive option over time.

Cable Selection Made Easy

THHN/THWN-2 and XHHW-2 are two common types of electrical wire insulation, differing primarily in their materials and performance characteristics. THHN/THWN-2 uses thermoplastic PVC insulation, making it lightweight, cost-effective, and easy to handle. However, it performs poorly in cold temperatures, becomes brittle below 14°F and emits toxic smoke when burned. It is also more susceptible to chemical damage and moisture leakage. In contrast, XHHW-2 features thermoset XLPE insulation, which provides greater durability, flexibility and chemical resistance. It remains functional in extreme cold down to -40°F and produces less toxic smoke in a fire. While XHHW-2 is more expensive initially, its enhanced safety, longevity and performance in harsh environments often make it a better long-term investment.

Wesco offers a full range of Service Wire XHHW-2 cables to provide long-term reliability for a variety of applications.  Our technical experts can help you select the right cable and streamline your project from planning to deployment.

Contact your local Wesco representative to learn more about our Service Wire offering.