Thermoset Insulated Wire (UL 44): What Every Buyer Must Know

Electrical installations across industrial plants, commercial complexes, and public infrastructure depend on wires that do far more than carry current. The insulation surrounding each conductor determines whether the wire can withstand heat, moisture, abrasion, and chemical exposure over decades of service. Among the many specifications available to electrical contractors and project engineers, thermoset insulated wire (UL 44) has earned a distinguished position for its exceptional thermal stability and long term reliability. At Dynamic Cables Limited, we have been manufacturing certified UL 44 compliant wire for export and domestic markets for over 39 years, and this guide consolidates everything a buyer, engineer, or procurement team needs to know before making a decision.

What Is a Thermoset Insulated Wire?

A thermoset material is defined as any polymer that, once cured by heat or chemical processes, cannot be remelted. Unlike thermoplastic materials that soften when heated back up again, thermoset compounds form permanent molecular crosslinks during curing which cannot be broken off again later. This irreversible structure gives thermoset insulation its core advantages: resistance to heat distortion, superior dielectric strength, and the ability to maintain mechanical integrity under sustained electrical load.

Cross linked polyethylene (XLPE) is one of the most frequently utilized thermoset insulation materials in the wire and cable industry. When conventional polyethylene is cross linked through radiation or chemical processes, its resultant compound remains dimensionally stable at elevated temperatures making it suitable for applications where sustained temperatures approach or exceed 90°C.

Understanding the UL 44 Standard

Underwriters Laboratories's (UL) product safety standard UL 44 provides guidelines for thermoset insulated wire and cable that meets its rigorous electrical, mechanical and environmental performance criteria. Dynamic Cables Limited manufactures this UL 44 listed wire under File Number E533878 so as to meet these benchmarks in every metre it ships out to customers.

Products covered under UL 44 include products with designation types XHHW-2, RHH and RHW-2 that each have specific performance implications. XHHW-2 denotes cross linked polyethylene insulation suitable for use in wet or dry locations up to 90°C. RHH and RHW-2 similarly cover thermoset constructions with equivalent thermal ratings, providing engineers with multiple compliant options depending on the application environment.

Key Construction Details

Conductor Options

Dynamic Cables Limited offers UL 44 wire in two conductor options:

• Copper Conductor: Class B compressed or compact stranded bare copper conforming to ASTM B3 and ASTM B8. Copper conductors are available in sizes ranging from 8 AWG through 1000 Kcmil.
• Aluminium Conductor: AA-8000 alloy compacted conductors in Class B stranding per ASTM B801. AA-8000 series aluminium alloy conductors address connection reliability challenges, making them a safe and approved choice under the National Electrical Code.

Insulation Material & Thickness

The insulation applied over the conductor is a thermoset cross linked polyethylene (XLPE) compound with a low coefficient of friction. Low friction surfaces reduce pulling tension during installation in conduit systems without needing lubricant. Insulation wall thickness ranges between 1.14 mm and 2.03 mm depending on AWG size to ensure consistent dielectric protection.

Electrical and Temperature Ratings

Dynamic Cables Limited's Thermoset Insulated Wire (UL 44) features an electrical voltage rating of 600V for residential/commercial use and up to 1000V in industrial configurations, with maximum allowable conductor operating temperature of 90°C in both dry and wet environments.

Compliance and Certifications

Our Jaipur facility produces every batch of UL 44 wire in accordance with ASTM B3, ASTM B8, ASTM B800, B801 and B836 standards. Flame performance is verified against UL 2256 (VW-1 vertical wire flame test). For conductors 1/0 AWG and larger, the wire carries the "FOR CT USE" marking for cable tray installation under the NEC. Our facilities hold ISO 9001:2015, ISO 14001:2015, and ISO 45001:2018 certifications, with CE certification and type test reports from CPRI, ERDA, and TAG Corporation.

Approved Applications Under the National Electrical Code

XHHW-2, RHH, and RHW-2 wires are classified as general purpose building wire approved for use in conduit, raceways, cable trays (1/0 AWG and above), and open air runs in both wet and dry locations under NEC guidelines.

Frequently Asked Questions

Q1. What is the difference between XHHW-2, RHH, and RHW-2 wire designations under UL 44?
All three designations fall under UL 44 and share a 90°C rating in both wet and dry conditions. XHHW-2 specifically uses cross linked polyethylene (XLPE) insulation, which offers a low friction surface and high abrasion resistance. RHH and RHW-2 cover broader thermoset compounds. Dynamic Cables manufactures all three under UL File Number E533878.

Q2. Can Dynamic Cables Limited supply UL 44 thermoset wire in aluminium conductor in addition to copper?
Yes. Dynamic Cables Limited manufactures UL 44 compliant thermoset wire in both copper and AA-8000 series aluminium alloy conductors (8 AWG through 1000 Kcmil) per ASTM B801 and NEC standards.

Q3. Is UL 44 thermoset insulated wire suitable for wet location installations?
Yes. XHHW-2 and RHW-2 designations carry a 90°C rating for both wet and dry locations, making them approved for underground conduit runs, outdoor raceways, and damp industrial environments.

Q4. What certifications and test reports does Dynamic Cables Limited provide with UL 44 wire?
Our UL 44 wire is listed under UL File Number E533878. We provide ISO 9001, 14001, 45001 certifications, CE marking, and independent type test reports from CPRI, ERDA, and TAG Corporation.

Q5. What is the standard packing format and lead time for UL 44 wire?
Standard packing is available in reel lengths of 500, 1000, 2500, and 5000 feet. Custom reel lengths and stranding configurations are available on request.

Conclusion

Thermoset insulated wire (UL 44) represents a technically superior choice for 600V and 1000V building wire applications demanding thermal resilience, moisture resistance, and code compliance. Dynamic Cables Limited brings certified manufacturing quality and independent certification into every reel we produce.