XHHW-2 vs THHN/THWN Wire
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 closer look at the differences between XHHW-2, THHN, and THWN building wires. These wires share very similar ratings and features. They both have a voltage rating of 600V and are both resistant to abrasion, heat, and moisture. So what is the difference between the two? Let's examine these wires and their differences.
What is Type XHHW Wire?
XHHW-2, or XLPE High Heat-Resistant Water-Resistant, Wire is a general-purpose wire suitable for use in conduit, raceways, feeders, and branch circuits. It is also often found in power distribution systems in industrial, commercial, and residential buildings.
It features XLPE (Cross-linked Polyethylene) insulation. Allied Wire and Cable offers XHHW Wire with both aluminum and copper conductors. The thermoset material used in this wire provides excellent heat and water resistance. The XHHW-2 specification has superseded the Type XHHW specification. XHHW-2 building wire has a maximum temperature of 90°C in dry and wet locations, whereas Type XHHW wire can only be used in temperatures as high as 75°C in wet locations.
What are THHN and THWN Wires?
THHN and THWN wire are single conductor building wires. This general-purpose wire is also suitable for installation in conduit and raceways. It is also suitable for use as machine tool, control circuit, or appliance wiring. These wires are PVC insulated with Nylon jackets. The thermoplastic PVC is flame-retardent and the nylon jacketing is resistant to gasoline and oil.
THHN stands for Thermoplastic High Heat-resistant Nylon-coated. THWN wire is the same, but the "W" stands for water-resistant. The main difference between these two standards is their maximum temperature in wet locations. THWN has a maximum temperature of 90°C in dry and wet locations, whereas THHN wire can only be used in temperatures as high as 75°C in wet locations. However, most of these wires, so you can use THHN and THWN interchangeably.
|Max. Temperature||Voltage Rating||Insulation||Jacket|
|XHHW||90°C dry locations, 75°C wet locations||600V||Cross-Linked Polyethylene (XLPE)||None|
|XHHW-2||90°C, dry and wet locations||600V||Cross-Linked Polyethylene (XLPE)||None|
|THHN||90°C dry locations, 75°C wet locations||600V||Polyvinyl Chloride (PVC)||Nylon|
|THWN||90°C, dry and wet locations||600V||Polyvinyl Chloride (PVC)||Nylon|
What's the difference between XHHW-2, THHN, and THWN wires?
The major difference between these two wires is their insulation. While XHHW-2 features XLPE, THHN and THWN feature PVC. This material is cheaper than XLPE but can emit toxic smoke if burned. THHN and THWN wire also have thinner insulation, making it more susceptible to current leakage and eventual breakdown. The Nylon coating in THHN and THWN wires also decreases their flexibility, making installation more difficult. XHHW-2 wire also features better low-temperature durability and electrical properties.
Even though these wires have the same voltage rating and application uses, it's clear they have their differences. Allied Wire and Cable carries an extensive stock of both XHHW-2, THHN, and THWN wire, including RoHS Compliant THHN Wire. Have more questions? Contact us today!