THWN-2 (UL 83) Thermoplastic Building Wire

1. Model Code & Compliance Standard

Letter Definition

T = Thermoplastic insulation H = High heat resistant W = Suitable for wet locations N = Nylon outer jacket -2 = Rated 90°C continuous operating temperature for both dry and wet conditions Traditional THWN only allows 75°C in wet areas; THWN-2 is the upgraded mainstream version with consistent 90°C rating all year round.

Certifications

Primary standard: UL 83 Thermoplastic Insulated Wires and CablesCompliant with NEC; VW-1 flame test per UL1581; nylon jacket offers oil and chemical resistance, widely adopted for indoor building wiring in North America.

2. Cable Construction (Inner to Outer)

1. Conductor Class B compact stranded bare annealed copper (standard configuration, aluminum rarely used); AWG range: 14AWG ~ 1000kcmil; smooth surface facilitates conduit pulling.

2. Inner PVC Insulation Heat-resistant modified thermoplastic PVC, provides primary insulation and thermal stability.

3. Nylon Outer Jacket Thin seamless nylon sheath, the distinctive feature of THWN series; Functions: oil resistance, chemical resistance, abrasion resistance, reduced pulling friction inside conduits.

3. Key Technical Specifications

Rated voltage: 600V AC Continuous temperature: constant 90°C for dry & wet indoor locations Short-circuit withstand temperature: max 150°C Cold bend performance: no cracking at -20°C Flame rating: UL VW-1 Minimum bending radius: 6 times cable outer diameter Installation limits: Only permitted inside conduits or enclosed cable trays; permanent outdoor sunlight exposure and direct underground burial are prohibited. Resistance: motor oil, grease, mild acid & alkali.

4. Main Advantages

1. Uniform 90°C rating delivers higher ampacity Superior to standard THWN (75°C wet rating); extra thermal margin for damp basements, kitchens and bathrooms.

2. Smooth dual-layer design simplifies conduit installation PVC insulation plus slippery nylon jacket lowers pulling tension for long, curved conduit runs; nylon prevents corrosion from oily residues inside pipes.

3. Comprehensive color coding for standardized wiring Available in black, red, blue, white, yellow, green etc., clearly differentiating phase, neutral and ground conductors in line with NEC codes.

4. Cost-effective indoor wiring solution Thermoplastic materials cost less than XLPE thermoset cables, the most common wire for residential and commercial indoor power distribution.

5. Good moisture resistance Safe for concealed wall cavities, ceilings and damp basement conduit runs.

5. Brief Comparison with XHHW-2 & RHW-2

THWN-2: UL83, PVC+nylon thermoplastic construction; limited to indoor conduit/tray only, no outdoor/underground use; economical household wiring XHHW-2: UL44, single-layer XLPE thermoset; no nylon jacket, lighter weight; indoor enclosed use only, poor oil & weather resistance RHW-2: UL44, EPR/XLPE+CPE thermoset dual layers; excellent weather, oil and abrasion resistance, approved for outdoor exposure, direct burial and industrial damp areas with higher cost.

6. Application Scope

1. Whole-house indoor wiring for residential buildings: outlets, lighting, air conditioning and water heater circuits

2. Concealed wiring inside walls and ceilings for malls, offices and hotels

3. Conduit wiring in damp basements, kitchens and bathrooms

4. Internal wiring for control panels and power equipment

5. Renovation replacement for outdated indoor electrical circuits