In our This vs. That series, we take a look at two similar products and define what makes them different. We hope that by doing this we can help you decided which products will work best in your next application. In this article, we take a look at XHHW2 wire and THHN/THWN wire and explain where they can be used.
XHHW2 wire and THHN/THWN wire are both categorized as building wire and share many features and ratings. These cables are approved for use in applications up to 600 volts and are resistant to abrasion, heat, and moisture. But how exactly do they differ? How do you know which to use? That depends on your desired price and insulation requirements.
XHHW2 wire is general-purpose wiring and is found in conduits, raceways, services, feeders, and branch circuits. It is also suitable for power distribution systems in industrial, commercial, and residential buildings.
XHHW2 insulation is similar to XHHW, which stands for “XLPE (Cross-linked Polyethylene) High Heat-resistant Water-resistant.” XHHW2 is rated for up to 90°C in dry or wet locations. XHHW is also a good choice for dry locations up to 90°C, but it is only recommended for 75°C wets. Because of its more desirable temperature rating, XHHW2 has superseded the XHHW specification.
THHN, or “Thermoplastic High Heat-resistant Nylon-coated,” is another electrical wire that can be run through conduits. Like XHHW2, THHN cable is commonly used in general purpose applications. You can also use it as a machine tool, control circuit, or appliance wiring.
It features flame-retardant Polyvinylchloride (PVC) insulation, and a Nylon coating protects it from gasoline and oil. Type THHN can only be used in dry locations not exceeding 90°C. Fortunately, many of these cables are now THHN/THWN dual rated, meaning they can also be used in wet locations up to 75°C (The W stands for "Wet-Resistant"). With a THWN2 rating, you can achieve a temperature rating of 90°C in both wet and dry locations.
How Do They Compare?
The main difference between these two building wires is that XHHW2 features XLPE insulation and THHN/THWN uses PVC.
This difference in materials makes THHN/THWN cheaper in price. However, when burned, PVC can emit toxic smoke, and because THHN/THWN is designed with a thinner PVC insulation, it is more susceptible to current leakage and eventual breakdown.
The nylon coating used for THHN/THWN wire also decreases the cable’s pliability, making installation more difficult. On the other hand, XHHW2 features a more flexible design that is easier to install. XHHW2 wire also features better low temperature and electrical properties than THHN/THWN wire, often making it the preferred choice of the two. Both XHHW2 wire and THHN/THWN wire can serve your electrical wire needs, but you should know the difference in cost, insulation, and electrical properties before making any purchase.
Search Allied Wire and Cable’s selection of XHHW and XHHW2 wire or our large variety of THHN/THWN cable to learn more about the cables’ features and benefits and to see which could be the better solution for your application.