You have seen it on spec sheets. You have seen it printed on wire jackets. "UL 44." It is one of those marks that everyone recognizes but few people fully understand.
What does UL 44 actually mean? Why does it matter for XHHW and XHHW-2 wire? And how does it affect the performance of the wire you install?
This article explains UL 44 in plain terms-what it covers, why it matters, and how it relates to XHHW/XHHW-2 wire applications.
1. What Is UL 44 and How Does It Relate to XHHW/XHHW-2?
UL 44 is the standard for thermoset-insulated wires and cables, published by Underwriters Laboratories. It covers XHHW and XHHW-2, along with other thermoset wire types.
Thermoset insulation (XLPE) undergoes a chemical cross-linking process during manufacturing. Once cross-linked, it cannot be remelted or reshaped. This gives it superior heat resistance, chemical resistance, and durability compared to thermoplastic materials like PVC.
The key difference between XHHW and XHHW-2 under UL 44: both are 90°C dry, but XHHW is only 75°C wet, while XHHW-2 is 90°C wet and dry.
A 10 AWG XHHW-2 wire with UL 44 marking has been tested for 90°C wet location performance and meets the standard's requirements. The certification provides documented proof of compliance.
UL 44 thermoset insulated wire XHHW-2 is designed for real-world conditions-not just lab tests.
2. Why UL 44 Matters for Installation Performance and XHHW-2 Applications
The UL 44 mark represents a set of tests that directly relate to how the wire performs on the job.
- Heat resistance. UL 44 requires thermoset insulation to maintain its electrical properties at elevated temperatures. For XHHW-2, this means 90°C in dry and wet conditions. In hot attics, near process heat, or in sun-exposed conduit, this matters.
- Chemical and abrasion resistance. UL 44 requires thermoset insulation to resist degradation from oils, chemicals, and moisture. In industrial environments with coolant, hydraulic fluid, and cleaning agents, this extends wire life. The insulation must also withstand pulling through conduit without damage.
- Insulation resistance. The standard requires specific minimum insulation resistance values. High insulation resistance means less leakage current and better safety.
Where XHHW-2 applications excel: wet locations (underground conduit, outdoor installations), high ambient temperatures, industrial environments, and cable tray systems. UL 44 certification is what enables these applications.
When you see a UL 44 wire specification, you know the wire has passed these tests.
3. UL 44 vs UL 83: Understanding the Difference
Many buyers confuse these two standards. They are different.
- UL 83 covers thermoplastic-insulated wires like THHN and THWN-2. PVC insulation with a nylon jacket. Suitable for many applications but has limitations in high-temperature or chemical-exposure conditions.
- UL 44 covers thermoset-insulated wires like XHHW and XHHW-2. XLPE insulation offers better heat resistance, moisture resistance, and chemical resistance than thermoplastic alternatives.
The difference affects which wire you choose. For wet locations, high-temperature environments, or chemical-exposure areas, UL 44 thermoset wire is the better choice.
For XHHW-2 applications in demanding environments, UL 44 certification is not optional-it is essential.
4. Three Common UL 44 XHHW-2 Specifications
Here are three XHHW-2 sizes covered under UL 44, each serving a different purpose.
- 10 AWG XHHW-2 Wire. For 30A branch circuits, equipment connections, and smaller feeders. UL 44 ensures 90°C wet/dry performance. XLPE insulation resists oil and chemicals. Easy to handle and terminates on standard lugs. Common for dedicated circuits in commercial buildings.
- 8 AWG XHHW-2 Wire. For 40-50A sub-feeders, large equipment, and HVAC units. UL 44 provides assurance for higher temperatures and damp conditions. XLPE maintains integrity where THHN would need derating. Specified when 10 AWG cannot meet the load but 6 AWG would be oversized.
- 4 AWG XHHW-2 Wire. For 85-95A main feeders, distribution panels, and large equipment. UL 44 is critical here-these circuits carry heavy loads, often over long distances. XLPE resists heat generated by high current and provides extra protection against chemical exposure in industrial settings. A common size for UL 44 wire specifications in commercial and industrial power distribution.
5. What to Look For and Common Misconceptions
What to check on a UL 44 spec sheet:
- UL mark. Should clearly show "UL 44" or "UL Listed." If not, the wire may not be certified.
- Temperature rating. Look for "90°C wet / 90°C dry" for XHHW-2. If it shows 90°C dry but only 75°C wet, it is XHHW, not XHHW-2.
- Insulation type. Should state "XLPE" or "thermoset." If it says "PVC" or "thermoplastic," it is not UL 44 thermoset wire.
- Voltage rating. UL 44 covers 600V, 1000V, and 2000V. Confirm it matches your system.
Common misconceptions:
All UL marks are the same. Different UL standards cover different wire types. UL 44 is for thermoset; UL 83 is for thermoplastic.
UL 44 means the wire is always better. It is the right standard for thermoset wires. "Better" depends on the application.
All XHHW-2 is UL 44. It should be. If a supplier offers XHHW-2 without UL 44 marking, something is wrong.
FAQ
Q1: What does UL 44 cover?
Thermoset-insulated wires and cables, including XHHW and XHHW-2. It defines requirements for conductor materials, insulation thickness, voltage ratings, temperature ratings, and testing procedures.
Q2: Why is thermoset insulation better than thermoplastic?
Thermoset (XLPE) is cross-linked, giving superior heat resistance, chemical resistance, and durability. Thermoplastic (PVC) can soften at high temperatures and degrade when exposed to chemicals.
Q3: What is the difference between UL 44 and UL 83?
UL 44 covers thermoset-insulated wires (XHHW, XHHW-2). UL 83 covers thermoplastic-insulated wires (THHN, THWN-2). Different standards for different wire types.
Q4: Does Greater provide UL 44 certified XHHW-2 wire?
Yes. Dongguan Greater Wire & Cable Co., Ltd. holds UL 44 certification. We can provide the certificate and file number upon request.
Need UL 44 Certified XHHW-2 Wire?
Tell us about your project-size, distance, and installation conditions. We will recommend the right UL 44 certified XHHW/XHHW-2 wire and send a quick quote.
Contact us
Dongguan Greater Wire & Cable Co., Ltd.
Tel/WhatsApp/Wechat: +86 136 6257 9592
Tel/WhatsApp/Wechat: +86 135 1078 4550
Email: manager01@greaterwire.com
Website: www.greaterwire.com