What Is THHN Wire?

Thermoplastic high heat nylon (THHN) wire is a single conductor general-purpose building and hook-up wire. The first letter T shows the insulation is a thermoplastic material made from polyvinyl chloride (PVC). The middle letters (HH) indicate it's high heat resistance, suitable for high-temperature use up to 90 degrees Celsius. The last letter, N, refers to the wire's abrasion- and heat-resistant nylon jacket. You'll find the letters THHN printed on the wire jacket.

Learn More about THHN Wire in the Allied University

TFFN Vs THHN Wire

MTW Vs THHN Wire

24 items

  • THHN 14 1
    $0.00 / 1000 FT
    • Ampacity (90C): 15
    • Approx LBS/MFT: 15.00
    • AWG Size: 14
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  • THHN 14 19
    $0.00 / 1000 FT
    • Ampacity (90C): 15
    • Approx LBS/MFT: 16.00
    • AWG Size: 14
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  • THHN 12 1
    $0.00 / 1000 FT
    • Ampacity (90C): 20
    • Approx LBS/MFT: 23.00
    • AWG Size: 12
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  • THHN 12 19
    $0.00 / 1000 FT
    • Ampacity (90C): 20
    • Approx LBS/MFT: 24.00
    • AWG Size: 12
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  • THHN 10 1
    $0.00 / 1000 FT
    • Ampacity (90C): 30
    • Approx LBS/MFT: 38.00
    • AWG Size: 10
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  • THHN 10 19
    $0.00 / 1000 FT
    • Ampacity (90C): 30
    • Approx LBS/MFT: 38.00
    • AWG Size: 10
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  • THHN 8 19
    $0.00 / 1000 FT
    • Ampacity (90C): 55
    • Approx LBS/MFT: 63.00
    • AWG Size: 8
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  • THHN 6 19
    $0.00 / 1000 FT
    • Ampacity (90C): 75
    • Approx LBS/MFT: 95.00
    • AWG Size: 6
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Where Is THHN Wire Used?

You use THHN cable for general-purpose residential and commercial building wiring. The cable's nylon jacket provides moderate protection against abrasion, and you must install THHN wire in a conduit or raceway. You may use THHN wire indoors and outdoors in dry and damp applications. Other applications for this wire include machine tools, appliances, and control circuits. Most types of THHN cable sold by AWC carry a dual thermoplastic high-temperature water-resistant nylon-jacket (THWN) rating, allowing their use in wet conditions.

THHN Conductor Materials

AWC stocks THHN cable made with pure copper conductors. THHN wires with a smaller diameter between 10 and 14 American Wire Gauge (AWG) have solid, soft-drawn, copper conductors. Larger THHN wires have stranded copper conductors.

THHN Wire Specifications

THHN wires have a thin flame-resistant PVC insulation covered by an abrasion-resistant nylon jacket. The wire is suitable for applications of up to 90ºC in dry locations and 75ºC in wet conditions, although you must correct the wire's ampacity at high ambient temperatures and when bundling cables together in a raceway or conduit.

The maximum voltage rating of the THHN cable is 600 volts. All THHN cables meet the UL 83 standard for safety thermoplastic-insulated wires and cables and the UL 106 Standard for safety machine-tool wires and cables. You can request Canadian Standards Association (CSA) approval, and certain THHN cables also have European Restriction of Hazardous Substances (RoHS) Directive approval.

THHN Cable Applications

Can You Use THHN Building Wire in a Rigid Conduit or Raceway?

You must install THHN wire in an approved conduit or raceway. You may not use THHN cable unless it's enclosed.

Can You Use THHN Wire Outdoors?

You can use THHN cable outdoors in dry and damp conditions, provided it is in a conduit. You must use THWN cable in wet conditions.

Can You Bury THHN Wire?

You may not bury THHN wire, although you may use it with a buried waterproof conduit or raceway.

Similar Wires and Cables

Similar wires and cables to THHN include THWN, thermoplastic, heat- and water-resistant wire (THHW), and thermoplastic flexible fixture nylon (TFFN):

  • THWN: THWN jacket that's suitable for use in dry (90ºC) and wet applications up to a maximum temperature of 75ºC. This wire has PVC insulation and a nylon jacket. Most THHN wires have a dual THHN/THWN rating.
  • THWN-2: Similar to THWN but rated for a maximum operating temperature of 90ºC in wet conditions.
  • THHW: THHW without a nylon jacket. It's suitable for dry use to a maximum temperature of 90ºC and wet applications to a maximum of 75ºC.
  • TFFN: TFFN wire for use in buildings. The wire is very flexible, has a nylon jacket, and is available in smaller gauges including 16 and 18 AWG.