THHN and THWN UL 83, 758, 1063, and 1581

THHN and THWN are commonly used thermoplastic, nylon-jacketed building wires for 600V applications, often combined as dual-rated THHN/THWN-2. THHN is designed for dry/damp locations up to 90°C, while THWN is engineered for wet/dry locations up to 75°C (or 90°C for THWN-2). They are ideal for conduit, feeders, and branch circuits.

THHN and THWN Key Differences and Features

Location Suitability: THHN is suitable only for dry locations, while THWN/THWN-2 is suitable for wet and damp locations, including outdoor conduit.

Temperature Ratings:

THHN: 90°C (194°F) in dry conditions.

THWN: 75°C (167°F) in wet/dry conditions (some versions are 90°C).

THWN-2: 90°C (194°F) in both wet and dry conditions.

THHN THWN Construction

Both feature a soft-annealed, stranded or solid copper/aluminum conductor, PVC insulation, and a nylon sheath for easy pulling.

Resistivity: Both are generally resistant to heat, moisture, oil, gasoline, and grease.

Common Use Cases

Used in commercial, industrial, and residential construction (e.g., inside conduit, machine tools, control circuits).

THHN AND THWN Building Wire

Insulation: PVC (Red, blue, black, brown, yellow, green, green/yellow or customized)

Jacket: Nylon

Maximum Operating Voltage: 600 volts

Maximum Conductor Temperature:

Dry locations (THHN): 90°C

Dry and wet locations (THWN): 75°C

In oil (Gasoline and Oil resistant II): 75°C

THHN THWN Features

1)Good resistance to moisture, heat, oil, gasoline, chemicals, and grease.

2)Suitable for installation where thermal overload exists.

3)Strict quality control during the manufacturing process.

4)Flame retardant, UL listed as VW-1.

5)Smooth nylon jacket aids in easier pulling.

6)Superior abrasion and mechanical properties.