THHN wire has a thin flame-resistant PVC insulation that is covered by an abrasion-resistant nylon jacket. THHN wires are suitable for applications up to 90ºC in dry locations and 75ºC in wet conditions. Although THHN wire can perform in high-temperature environments, 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, as well as the UL 1063 standard for safety machine-tool wires and cables. You can request Canadian Standards Association (CSA) approval if desired, and certain THHN cables also meet the European Restriction of Hazardous Substances (RoHS) Directive for hazardous material compliance.
Contact Allied Wire & Cable to learn more or request a quote.
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THHN 14 10.00 / 1000 FT
- Ampacity (90C): 15, 25
- Approx LBS/MFT: 15.00, 16, 64.30
- AWG Size: 14
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What does THHN mean?
THHN stands for Thermoplastic High Heat-resistant Nylon-coated — a common single-conductor building wire with PVC insulation and a nylon jacket.
The first letter “T” indicates a thermoplastic insulation made from polyvinyl chloride (PVC). The middle letters “HH” show that the wire is rated for high-temperature use up to 90°C. The final letter “N” refers to the wire’s abrasion- and heat-resistant nylon jacket. The letters “THHN” are printed directly on the wire jacket to identify the cable's rating.
What type of conductor does THHN wire have?
THHN wire uses either solid or stranded soft-drawn copper conductors depending on gauge size.
Smaller sizes between 10 and 14 AWG typically feature solid copper conductors. Larger sizes use stranded copper conductors for flexibility and higher current capacity. Allied Wire & Cable offers THHN cable made with pure copper conductors across the full range of sizes.
Where is THHN wire used?
THHN wire is used in general-purpose residential, commercial, and industrial building wiring where conduit or raceway protection is required.
Its abrasion-resistant nylon jacket makes it suitable for installation in both dry and damp environments. Common applications include:
- Branch circuits for power and lighting
- Machine tools and industrial equipment
- Appliances and HVAC systems
- Control circuits in building systems
THHN wire must be installed in a conduit or raceway. Most THHN cable sold by Allied Wire & Cable carries a dual THHN/THWN rating, which permits its use in wet environments.
What standards does THHN wire meet?
THHN wire meets UL 83 and UL 1063 safety standards and is available with CSA and RoHS compliance.
- UL 83: Thermoplastic-insulated wires and cables
- UL 1063: Machine-tool wires and cables
- CSA Approval: Available upon request for Canadian applications
- RoHS Directive: Select THHN cables meet European hazardous substance restrictions
What are the alternatives to THHN wire?
Common THHN alternatives include THWN, THWN-2, THHW, and TFFN — each designed for different thermal, moisture, and installation requirements.
- THWN: Rated 90°C dry / 75°C wet. Nylon jacket. Often dual-rated with THHN.
- THWN-2: Rated 90°C in both dry and wet conditions. Improved water resistance.
- THHW: Similar to THHN but without a nylon jacket. 90°C dry / 75°C wet.
- TFFN: Flexible, nylon-jacketed wire for fixture use. Available in 16–18 AWG.
What is the difference between THHN and THWN wire?
THHN is rated for dry locations, while THWN includes water resistance for wet environments.
Modern THHN wire is often dual-rated as THHN/THWN. THHN alone is not suitable for wet conditions unless also marked as THWN or THWN-2. Always verify labeling for application-specific compliance.
What sizes does THHN wire come in?
THHN wire is available from 18 AWG up to 4/0 AWG, covering a wide range of residential and industrial applications.
Common sizes include:
- #2, #3, #6: Panel feeds and large branch circuits
- 2/0 AWG: High-power distribution and feeder circuits
What is 2 AWG THHN wire used for?
2 AWG THHN wire is used in feeders, branch circuits, and industrial applications requiring high ampacity and durability.
This size delivers 95 amps at 90°C and is often used for high-load systems in commercial and industrial installations.
What does “THHN” stand for?
THHN stands for Thermoplastic High Heat-resistant Nylon-coated.
The designation reflects the wire’s PVC insulation and nylon jacket, which together provide thermal resistance and physical protection in dry applications.
Is there a THHN wire size chart?
Yes — THHN ampacity varies by wire gauge. Use the chart below to determine current-carrying capacity and application suitability.
| AWG Size | Conductor Type | Ampacity (90°C) | Common Applications |
|---|---|---|---|
| 14 AWG | Solid | 15 Amps | Lighting circuits |
| 12 AWG | Solid | 20 Amps | Residential wiring |
| 10 AWG | Solid | 30 Amps | Water heaters, AC units |
| 8 AWG | Stranded | 40 Amps | Electric dryers, ovens |
| 6 AWG | Stranded | 55 Amps | Subpanels, heavy equipment |
| 4 AWG | Stranded | 70 Amps | Service feeders |
| 2 AWG | Stranded | 95 Amps | Industrial branch circuits |
| 1/0 AWG | Stranded | 150 Amps | Main service entrance |
| 2/0 AWG | Stranded | 175 Amps | Large feeders, motors |
| 4/0 AWG | Stranded | 230 Amps | High-load industrial circuits |
THHN vs. THWN vs. THWN-2 vs. THHW Comparison
Each wire type differs in moisture rating, jacket, and typical use — all affect code compliance and application fit.
| Feature | THHN | THWN | THWN-2 | THHW |
|---|---|---|---|---|
| Dry Rating | 90°C | 90°C | 90°C | 90°C |
| Wet Rating | 75°C (if dual-rated) | 75°C | 90°C | 75°C |
| Jacket | Nylon | Nylon | Nylon | None |
| Water Resistance | No (unless dual-rated) | Yes | Yes | Yes |
| Typical Use | Dry conduit, building wire | Damp conduit | Wet conduit | Conduit, flexible installations |
| Insulation | PVC | PVC | PVC | PVC |
| Dual Rated? | Often THHN/THWN | — | — | No |
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