Southwire 500-ft 12 -AWG Yellow Stranded Copper THHN wire ( By-the-roll )

The Southwire 12 AWG THHN is the single-conductor wire that commercial and industrial electricians pull through conduit for 20-amp branch circuits, feeders, and general building wiring in commercial offices, retail spaces, industrial facilities, and multi-family residential projects. As a 12 AWG stranded copper THHN conductor, this product uses 19-strand copper construction that flexes smoothly through conduit bends without the stiffness of solid copper, which matters meaningfully when running long conduit pulls with multiple 90-degree elbows. The yellow THHN wire 500 ft spool size is the standard commercial roll length, sufficient for typical mid-size project consumption while remaining single-installer manageable. As a THHN THWN-2 12 gauge dual-rated conductor, the same wire serves both dry locations (THHN rating, 90 degrees Celsius) and wet locations (THWN-2 rating, 75 degrees Celsius in wet conditions), eliminating the need to stock separate dry-location and wet-location wires for projects that mix indoor and outdoor conduit runs. The Southwire THHN by the roll format provides project-scale wire supply in a single SKU that fits typical commercial bill-of-materials estimating. Every Southwire 12 AWG THHN spool is UL Listed, RoHS compliant, manufactured in the USA, and ships nationwide from IB Lighting with free freight and contractor volume pricing. Manufacturer specifications are available at the official Southwire website.

Southwire 12 AWG THHN Key Highlights

What THHN Wire Is (And Why It Goes In Conduit)

THHN stands for Thermoplastic High Heat-resistant Nylon-coated wire, and the Southwire 12 AWG THHN is the single-conductor building wire that commercial electricians pull through conduit for branch wiring. Understanding what THHN is and how it differs from cable products like NM-B Romex matters because each is correct for different installation environments.

THHN consists of a single insulated conductor: copper conductor surrounded by PVC primary insulation, which is then surrounded by a tough nylon outer jacket. Multiple THHN conductors are pulled together through conduit (typically 3 to 6 conductors depending on the circuit configuration and conduit fill capacity) to form a complete branch circuit. The conduit itself provides the mechanical protection that NM-B Romex achieves through its outer jacket, which is why THHN installations require less self-contained protection in the wire jacket itself.

The conduit-and-conductor approach has meaningful advantages for commercial and industrial installations. Conduit allows future changes to the wiring (additional circuits added, conductors replaced, or wire upgraded) without opening walls or ceilings. Conduit also provides better protection against physical damage, rodent damage, and certain environmental hazards. For installations where the wiring will be exposed (factory floors, parking garages, mechanical rooms) or where future modifications are likely (commercial office spaces, retail buildouts), conduit is the right choice and THHN is the wire that goes inside it.

The Southwire 12 AWG THHN is specifically the 12 AWG size, which is the most common commercial branch wire size for 20-amp circuits. Commercial buildings typically wire general receptacles and lighting on 20-amp branches (more capacity per circuit than residential 15-amp branches), and 12 AWG THHN handles these branches throughout the structure.

THHN vs THWN-2 Dual Rating: One Wire for Dry and Wet Locations

The Southwire 12 AWG THHN carries both THHN and THWN-2 ratings printed on the same conductor, which means a single wire can serve both dry and wet location applications. Understanding what each rating means clarifies when and how the wire can be used.

THHN rating (Thermoplastic High Heat-resistant Nylon-coated): The wire is rated for use in dry locations at temperatures up to 90 degrees Celsius. This is the standard rating for indoor conduit installations including commercial branch wiring, panel feeders inside electrical rooms, and general indoor building wiring. The 90C rating gives higher ampacity ratings under NEC ampacity tables, which means the same 12 AWG conductor can carry more current under dry indoor conditions than it could without the high-heat rating.

THWN-2 rating (Thermoplastic Heat- and Water-resistant Nylon-coated, version 2): The wire is rated for use in wet locations at temperatures up to 75 degrees Celsius. Wet locations include outdoor conduit (subject to rain, snow, condensation), underground conduit, and indoor conduit in damp environments (basements, mechanical rooms with humid conditions, food service areas with washdown requirements). The wet location rating expands the wire’s approved use cases significantly beyond what a dry-only conductor could serve.

The dual rating on the Southwire 12 AWG THHN simplifies project bill-of-materials planning. Rather than stocking separate dry-location and wet-location wires for projects that include both indoor branches and outdoor or underground conduit runs, contractors stock the dual-rated conductor and use it for all applications. This reduces inventory complexity, eliminates the risk of pulling the wrong wire type into a wet-location conduit, and provides flexibility for design changes that might shift conduit runs from dry to wet location classifications during the project.

The “THWN-2” designation specifically (rather than just “THWN”) indicates the newer wet-location specification with improved insulation chemistry that maintains its rated properties for longer service life in wet conditions. THWN-2 is the current Southwire standard for THHN wire, replacing the older THWN specification.

Stranded Copper Construction: Why It Matters for Conduit Pulls

The Southwire 12 AWG THHN uses stranded copper construction rather than solid copper. This is a deliberate choice for conduit-installed wire, and it makes meaningful difference in installation labor and long-term reliability.

Stranded conductors consist of multiple smaller copper wires twisted together to form the conductor of equivalent overall gauge. The 12 AWG THHN uses 19-strand construction, which means 19 individual copper wires twisted into the 12 AWG conductor. The stranded construction flexes much more easily than solid copper, which matters when pulling wire through conduit with multiple 90-degree elbows, long horizontal runs, and tight bend radii.

Solid copper conductors resist bending and tend to retain whatever shape they are forced into. For a long conduit run with three or four 90-degree elbows, solid copper conductors require significantly more pull force and are meaningfully more likely to bind in the conduit, jam at the elbows, or kink during installation. Stranded copper flexes around bends naturally, slides past obstructions, and finishes the pull with less effort.

For 12 AWG and larger conductors in conduit applications, stranded is the industry standard. For 14 AWG and smaller (which are smaller-diameter conductors with less inherent stiffness), solid is sometimes acceptable. The Southwire 12 AWG THHN uses 19-strand because that strand count gives the right balance between flexibility (more strands flex better) and termination simplicity (fewer strands are easier to terminate at devices and lugs).

Yellow Color Code: Industry-Standard Sizing Identification

The Southwire 12 AWG THHN uses bright yellow PVC insulation, which is the universal industry color for 12 AWG copper conductors across both THHN and NM-B (Romex) wire types. The color coding system makes wire gauge instantly identifiable on the jobsite without measuring or reading labels: white for 14 AWG, yellow for 12 AWG (this wire), orange for 10 AWG, and black or other colors for larger sizes.

The yellow color also helps with circuit identification during installation. When pulling multiple branches through the same conduit system, electricians often pull yellow 12 AWG conductors for the 20-amp branches alongside other gauges (10 AWG orange for 30-amp branches, 8 AWG black for larger feeder runs). The color difference makes circuit-by-circuit identification straightforward without paper labels or marker codes.

For multi-conductor circuit installations using THHN, the standard practice is to vary the color of the conductors within a single circuit for hot/neutral/ground identification. A typical 20-amp branch in conduit uses one black conductor (hot), one white conductor (neutral), and one green conductor (ground), with all three being 12 AWG THHN. The yellow specifically is used for branch circuits where the color matches the gauge identification (often when running multiple branches through the same conduit), or as a hot leg in specific industrial color-coding schemes.

Common Applications for the Southwire 12 AWG THHN

The Southwire 12 AWG THHN is the workhorse conductor for 20-amp commercial branch wiring in conduit installations. The most common applications include:

• Commercial branch circuits in EMT conduit. Office buildings, retail spaces, restaurants, medical facilities where 20-amp branches run through metal conduit.
• Industrial branch wiring. Manufacturing facilities, warehouses, and light industrial buildings where conduit installations are standard practice.
• Wet-location outdoor conduit runs. Parking garage lighting, exterior wall packs, building perimeter circuits where PVC or rigid steel conduit runs outdoors.
• Underground conduit runs. PVC conduit buried per NEC depth requirements for site lighting, parking lot lighting, exterior buildings on a single property.
• Commercial kitchen and equipment circuits. Restaurant kitchens, food service facilities where conduit protection is required for sanitation and code compliance.
• Pull through conduit during major remodels. Renovation work where existing conduit infrastructure is reused with new wire installed.
• Transfer switch wiring for standby generators. Generac transfer switch installations often use THHN in conduit between the generator and the transfer switch.
• EV charger circuit installations. Some Tesla and other EV charger installs route the high-amperage circuit through conduit using THHN conductors.

For residential branch wiring in framed wood construction, NM-B Romex (the Southwire 12/2 NM-B 250 ft Romex SIMpull) is typically more cost-effective and code-compliant. THHN is the right choice when conduit is the installation method, when wet-location applications require the THWN-2 rating, or when commercial or industrial code requires conduit-protected wiring.

Conduit Fill and Bundling Considerations

Pulling the Southwire 12 AWG THHN through conduit requires attention to fill capacity and bundling derating rules under the National Electrical Code. These rules limit how many conductors can fit in a given conduit size and how ampacity must be adjusted when multiple current-carrying conductors run together.

NEC conduit fill tables specify the maximum number of conductors that fit in each conduit size based on the conduit’s cross-sectional area and the conductor’s insulation dimensions. For 1/2-inch EMT conduit (the most common smaller commercial conduit size), approximately 9 conductors of 12 AWG THHN can be pulled. For 3/4-inch EMT, approximately 16 conductors. For 1-inch EMT, approximately 26 conductors. These limits prevent excessive pulling friction and ensure heat dissipation during current flow.

Ampacity derating applies when more than 3 current-carrying conductors are bundled in a single conduit. NEC Article 310 derating tables specify reduced ampacity values when conductors are bundled: 4 to 6 conductors = 80% of base ampacity, 7 to 9 conductors = 70%, 10 to 20 conductors = 50%. For the Southwire 12 AWG THHN with a base 75C ampacity of 25 amps in conduit, a bundled installation of 6 conductors would derate to 20 amps, which is the design value for a typical 20-amp branch circuit.

Most commercial branch circuit installations run 3 current-carrying conductors per conduit (a single 3-wire branch with hot, neutral, and ground), which falls within the unbundled ampacity tables without derating. Multi-branch installations through shared conduit require the derating calculation, which is handled by the design engineer during the electrical design phase.

THHN vs NM-B Romex: When to Use Which

The Southwire 12 AWG THHN and the Southwire 12/2 NM-B Romex SIMpull both serve 20-amp branch circuit applications, but they are fundamentally different products with different correct installation environments. Choosing the right one matters because using the wrong type creates code violations that fail inspection.

Choose Southwire 12 AWG THHN if your installation uses conduit, if your project is commercial or industrial, if you need wet-location capability (outdoor or underground conduit), or if future wiring changes are anticipated and conduit accessibility is desired. THHN is the single-conductor format that pulls through conduit, with separate hot, neutral, and ground conductors run through the same conduit. The stranded copper construction handles bends smoothly through conduit elbows.

Choose NM-B Romex like the Southwire 12/2 NM-B if your installation is residential single-family construction with wood framing, if the wire runs through wall cavities and ceiling joists rather than conduit, or if the cost-effectiveness of the integrated multi-conductor cable format suits the project scope. NM-B is the integrated cable format that includes hot, neutral, and ground conductors plus an outer jacket in a single cable, eliminating the conduit step entirely for residential framing applications.

For most US residential single-family construction, NM-B is the standard. For most commercial and industrial construction, THHN-in-conduit is the standard. Mixed projects (a residential remodel with a small commercial space, or a commercial space with limited residential-style framing) may use both types in different areas of the same project. The IB Lighting team can help specify the right wire types for any project scope.

Code Compliance and Ratings

The Southwire 12 AWG THHN is UL Listed and meets every requirement of the National Electrical Code for residential, commercial, and industrial branch wiring in conduit. The wire is governed by NEC Article 310 (Conductors for General Wiring) and the THHN/THWN-2 specifications, which differ from NEC Article 334 that governs NM-B residential branch cable.

Key code specifications: 600-volt insulation rating (covers residential 120/240V and commercial 277/480V applications), 90 degrees Celsius dry-location rating (THHN), 75 degrees Celsius wet-location rating (THWN-2), and approved use in raceways (conduit) and certain cable assemblies. The wire is NOT approved for use without conduit protection in residential framed construction; the multi-conductor NM-B Romex format is the correct product for those applications.

The Southwire 12 AWG THHN is also RoHS compliant, which means it meets European Union Restriction of Hazardous Substances directive requirements. While RoHS is a European specification, RoHS compliance has become a standard procurement requirement for many federal, state, and corporate buyers in the United States as well. RoHS-compliant wire is eligible for certain government procurement contracts and corporate sustainability programs.

Made-in-USA manufacturing is another procurement-relevant attribute. Federal procurement contracts including those covered by the Buy American Act often require domestically-manufactured electrical products. The Southwire 12 AWG THHN is manufactured in the United States, which qualifies it for these federal procurement applications. State procurement contracts in California, Texas, and other states with Buy American provisions also accept the domestically-manufactured Southwire products.

Southwire 12 AWG THHN Specifications

Southwire 12 AWG THHN FAQs

Who the Southwire 12 AWG THHN Is Built For

The Southwire 12 AWG THHN serves three clear buyer types. The first is commercial electrical contractors running fit-outs, tenant improvements, office buildouts, retail installations, restaurant projects, medical facility wiring, and similar commercial branch circuit work where conduit-and-conductor is the standard installation method. For these buyers, the Southwire 12 AWG THHN is the workhorse 20-amp branch wire that gets pulled on most every project. A typical commercial tenant build-out covering 20 to 40 branch circuits often consumes 6 to 12 spools of 12 AWG THHN, and the 500-foot spool size matches project consumption.

The second buyer is the industrial electrician handling branch wiring, control circuits, and general equipment power in manufacturing facilities, warehouses, and similar industrial environments. For these buyers, the THWN-2 wet-location rating matters because industrial environments often include damp conditions (food processing, chemical handling, equipment washdown areas) where dry-only conductors would not be code-compliant. The Southwire 12 AWG THHN dual rating serves both dry and wet industrial applications without requiring separate wire stocks.

The third buyer is the multi-family residential builder or remodeler working on projects where conduit is required by code or chosen by design preference. Apartment buildings, condominium projects, dormitories, and similar multi-unit residential construction often use conduit-and-THHN rather than NM-B Romex for branch wiring, particularly in jurisdictions with stricter code requirements. The Southwire 12 AWG THHN serves these multi-family applications alongside the Southwire Armorlite 12/2 MC cable for buildings where mixed wire types are specified. Browse the broader IB Lighting electrical wire collection for the complete range of THHN, NM-B, MC, and other cable types.

THHN-in-Conduit vs MC Cable: Which Should You Use?

Within commercial branch wiring, the Southwire 12 AWG THHN-in-conduit competes against MC (Metal Clad) cable like the Southwire Armorlite 12/2 MC cable. Both are code-compliant for most commercial branch applications, but the choice between them is driven by labor cost, installation conditions, and specific code or fire-rating requirements.

Choose Southwire 12 AWG THHN-in-conduit if your project requires conduit-encased wiring for specific code reasons (certain plenum applications, specific fire-rated assemblies, jurisdictions with stricter conduit requirements), if you need future flexibility to add or change conductors without re-pulling cable, or if your installation is in an environment where MC cable armor is not appropriate. THHN also tends to be the right choice for very long branch runs where the rigidity of conduit aids cable management, and for any installation where wet-location conduit is required (the THWN-2 rating handles these without requiring different wire).

Choose MC cable like the Southwire Armorlite 12/2 MC cable if your project benefits from the meaningful labor savings of skipping the conduit installation step. MC cable provides mechanical protection equivalent to wire-in-conduit through its integrated metal armor, without the labor of conduit installation. The Southwire Armorlite 12/2 MC cable delivers the same 20-amp 12 AWG circuit capacity with one-third to one-half the labor hours of equivalent THHN-in-conduit work, which is the primary economic argument for specifying MC cable on commercial branch wiring.

For most modern commercial branch wiring projects in standard construction, MC cable has become the default specification. THHN-in-conduit is reserved for the specific applications where conduit is genuinely the better choice. Both Southwire products are stocked at IB Lighting, and our team can help specify the right cable type for your project’s specific scope and code requirements.

Installation Tips for the Southwire 12 AWG THHN

Pulling the Southwire 12 AWG THHN through conduit follows specific best practices that improve labor efficiency and inspection pass rates. First, plan the conduit run before pulling wire: install the conduit completely, including all junction boxes, pull boxes, and fittings, before any wire goes into the system. Pulling wire through partially-installed conduit creates more friction and pull complexity than pulling through a complete conduit run.

Use pulling lubricant to reduce friction on long pulls. Wire pulling compound applied to the leading conductor end (and re-applied as needed during the pull) cuts pulling force significantly, which protects both the wire and the conduit from damage during installation. For multi-conductor pulls (typical of branch circuits), bundle the conductors together with a pulling head (a small metal or plastic device that grips multiple conductors at once) so they pull as a unit rather than splaying apart in the conduit.

Maintain bend radius limits per NEC requirements. The minimum bend radius for THHN is determined by the conduit bend radius, since the wire follows the conduit path. Sharp bends in conduit (such as those formed by older conduit work or improperly bent EMT) can damage wire insulation during pulls or restrict ampacity if the wire is binding. Inspect conduit bends visually before pulling and re-form any tight bends.

For terminations at boxes and devices, strip about 8 inches of jacket and insulation back to expose the stranded copper conductor. Use linesman pliers to twist the strands together at terminal screws (or use a crimp-on lug for larger devices). Torque all terminations to the device manufacturer’s specification using a torque screwdriver, since loose terminations cause both safety hazards and unreliable circuit operation over time.

Bulk and Contractor Pricing

The Southwire 12 AWG THHN is one of IB Lighting’s most-stocked commercial wire SKUs because contractors buy THHN in volume on most every commercial fit-out project. We offer automatic volume pricing on multi-roll orders, with deeper savings on larger bills of materials. A typical commercial fit-out covering 20 to 40 branch circuits often consumes 6 to 12 spools of 12 AWG THHN alongside other gauges (10 AWG for 30-amp circuits, 14 AWG for 15-amp lighting branches, larger sizes for feeders), and these combined orders trigger our standard contractor pricing tier.

Free freight applies to every Southwire 12 AWG THHN 500-foot spool order regardless of quantity. Most orders ship within 1 to 2 business days and arrive within 5 to 6 business days. If you need a bill of materials priced and quoted before you order, the IB Lighting team can turn around a quote inside of a business day for most projects. Browse our complete electrical wire collection for the full range of THHN gauges, NM-B Romex residential cable, and other electrical supplies needed for project completion.

Browse the complete IB Lighting electrical wire and cable collection, compare against the Southwire 12/2 NM-B Romex SIMpull 250 ft (residential cable alternative) or the Southwire Armorlite 12/2 MC cable 250 ft (commercial cable alternative), explore other Southwire products, or visit our customer FAQ hub. Manufacturer technical sheets are available at the official Southwire website.