Southwire 250-ft 12 / 3 / Romex SIMpull Solid Indoor CU NM-B W/G Individual pack ( By-the-roll )

The Southwire 12/3 NM-B 250 ft Romex SIMpull is the residential branch circuit cable that contractors pull whenever an installation needs more than two current-carrying conductors. As 12/3 wire with ground, the Southwire 12/3 NM-B 250 ft includes three insulated 12 AWG copper conductors plus a bare copper equipment ground, all enclosed in a yellow PVC jacket. The 12/3 Romex SIMpull jacket is the SIMpull friction-reducing version of standard NM-B, which cuts pull effort by roughly 50 percent compared to legacy Romex and meaningfully speeds up installation through bored studs and joists. As an NM-B 12/3 cable 250 ft spool, the unit length matches what most three-way switch runs, 240V appliance installs, and multi-wire branch circuits actually consume on a typical residential project. As a 12/3 indoor electrical wire rated for 600V at 90 degrees Celsius in dry locations, every Southwire 12/3 NM-B 250 ft spool is UL Listed, made 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 12/3 NM-B 250 ft Key Highlights

12/3 Romex SIMpull: Why the SIMpull Jacket Matters More on 12/3 Runs

The defining feature of the Southwire 12/3 NM-B 250 ft Romex SIMpull is the SIMpull jacket itself. Standard NM-B jackets have always been a friction surface, especially when pulled through bored holes in framing studs or stacked through multiple knockouts in a panel. SIMpull is Southwire’s friction-reducing surface treatment that turns a sticky pull into something closer to a pipe slide. Independent contractor testing puts the friction reduction at roughly 50 percent compared to legacy non-SIMpull NM-B, which translates directly into faster rough-in and less crew exhaustion at the end of a long day.

The SIMpull advantage is even more meaningful on 12/3 cable than on 12/2 because 12/3 is physically larger and stiffer. Three insulated conductors plus a ground wire packs more bulk inside the jacket, which means more friction against framing during long pulls. SIMpull compensates for that bulk and keeps 12/3 installations practical to pull single-handed in most residential configurations. For a 250 foot spool of 12/3 Romex SIMpull, the practical impact shows up most on the long horizontal runs through ceiling joists that three-way switching circuits typically require, where standard 12/3 cable would bind frequently and require a second person to feed.

12/3 Wire with Ground: Why Three Conductors Plus a Bare Ground

The “12/3 with ground” specification on the Southwire 12/3 NM-B 250 ft tells you everything about the conductor configuration. The “12” is the AWG gauge, which determines the current-carrying capacity of the wire. 12 AWG copper is rated for 20 amps in the National Electrical Code residential branch circuit table. The “3” means three insulated current-carrying conductors. In NM-B 12/3, these are typically a black hot, a red hot (or “traveler” depending on the application), and a white neutral. The “with ground” portion is the bare copper equipment grounding conductor that runs alongside the insulated conductors inside the jacket.

The third insulated conductor is the key feature that distinguishes 12/3 from 12/2. The extra conductor lets you wire installations that 12/2 simply cannot handle: three-way switches that need a traveler between switch locations, 240V circuits that need two hots without a shared neutral path, multi-wire branch circuits that share a neutral between two hot conductors on opposing phases, and a few other less-common configurations. Without the third conductor, none of these wiring schemes are possible with a single cable run.

Common Applications for the Southwire 12/3 NM-B 250 ft

The Southwire 12/3 NM-B 250 ft Romex SIMpull is the cable contractors specifically reach for when an installation goes beyond what 12/2 can handle. The most common applications include:

• Three-way and four-way switch runs. Lighting circuits controlled from two or more locations, like staircases, hallways, large rooms with multiple entries.
• 240V appliance branches. Some 20-amp 240V applications use 12/3 to provide both hots and a neutral for 120/240V appliances that need both voltages.
• Multi-wire branch circuits. Two 20-amp circuits sharing one neutral conductor, common in kitchen counter receptacles where code requires two separate small-appliance branches.
• Receptacles with split-wired switching. Half-switched outlets where one receptacle on a duplex is always-hot and the other is switched.
• Generator transfer switch interconnects. The neutral, two hots, and ground conductors needed between a generator transfer switch and certain panel configurations.
• Whole-house fan and ceiling fan installations. Where separate switching for fan and light functions requires the extra traveler conductor.

For simpler 20-amp branch circuits like general household receptacles, kitchen counter outlets, or single-pole switched lighting, 12/2 NM-B is the correct cable and is less expensive per foot. The Southwire 12/3 NM-B 250 ft is specifically the right pick when the installation demands the third conductor.

Three-Way Switch Wiring: The Most Common Use of 12/3

The single most common application for the Southwire 12/3 NM-B 250 ft is three-way switch wiring. A three-way switch lets you control a single light fixture from two different locations, like both ends of a hallway or at the top and bottom of a staircase. The wiring requires running cable between the two switch locations that includes three current-carrying conductors plus a ground: typically one conductor as the common (carrying the switched output to the light), and two conductors as travelers (carrying the on/off state between the two switches).

A standard three-way switch installation uses 12/2 to bring power to the first switch box, then 12/3 between the two switch boxes (this is the traveler run), then either 12/2 or 12/3 from the second switch to the light fixture depending on how the circuit is laid out. The Southwire 12/3 NM-B 250 ft 250 foot spool is sized to handle multiple three-way switch traveler runs in a typical residential rough-in, with enough leftover cable for one or two simple 240V appliance branches or shared neutral applications elsewhere in the project.

Four-way switches (where you control a light from three or more locations) also use 12/3 between the four-way switch and each of the two three-way switches in the circuit. For these more complex switching scenarios, 12/3 is even more essential, and a 250 foot spool may be quickly consumed in larger homes with extensive switched lighting.

240V Circuits Using 12/3

The Southwire 12/3 NM-B 250 ft also serves 240V appliance circuits, particularly the 120/240V combination circuits used by some kitchen ranges, dryers, and similar appliances. These appliances draw 240V for the heating elements but also need 120V for controls, lighting, and accessories, which means the circuit needs both hot conductors (carrying the 240V differential) plus a neutral conductor (providing the 120V reference).

For 20-amp 240V applications, 12/3 NM-B is the correct cable. Larger appliances like ranges and dryers typically need 30-amp or 50-amp circuits using larger gauges (10/3 or 6/3 respectively), but smaller 240V applications fall within 12/3’s 20-amp rating. Common 20-amp 240V applications include some shop tools, smaller HVAC equipment, and certain commercial-grade kitchen appliances.

Multi-Wire Branch Circuits with Shared Neutral

One advanced application for the Southwire 12/3 NM-B 250 ft is the multi-wire branch circuit, where two separate 20-amp circuits share one neutral conductor instead of each having its own. This is a code-compliant and labor-efficient way to wire two circuits using a single cable run, which saves labor and material on installations that need multiple branches running to the same area.

The classic example is kitchen counter receptacles. The National Electrical Code requires two separate 20-amp small-appliance branch circuits in residential kitchens, and a single 12/3 NM-B run can serve both circuits if the two hots are connected to opposing phases (typically using a double-pole 20-amp breaker). The shared white neutral handles the unbalanced load between the two circuits, which is electrically clean as long as the hots are on opposing phases.

Multi-wire branch circuits require careful breaker selection (the breakers serving both hots must be tied together so a single breaker trip de-energizes both hots simultaneously, per NEC) and careful labeling for inspector approval. Most installers use a double-pole breaker rather than two single-pole tied breakers to satisfy the simultaneous-trip requirement cleanly. The Southwire 12/3 NM-B 250 ft is the right cable choice for these multi-wire branch installations.

Code Compliance and Ratings

The Southwire 12/3 NM-B 250 ft Romex SIMpull is UL Listed and meets every requirement of the National Electrical Code (NEC) for residential branch circuit wiring. The cable carries a 600-volt insulation rating with a 90-degree Celsius temperature rating in dry locations. NM-B specifically means “Non-Metallic, B-rated,” which is the code designation for the residential branch circuit cable approved for installation in dry, indoor locations protected from physical damage by the building structure.

NM-B is not approved for wet locations, direct burial, conduit fill in damp environments, or exterior installations where the cable would be exposed to weather. For those applications, UF (Underground Feeder) cable, THHN/THWN conductors in conduit, or Type SE service entrance cable are the correct alternatives. The yellow jacket color of the 12/3 NM-B is part of the industry-standard color coding system: yellow for 12 AWG, white for 14 AWG, orange for 10 AWG, and black for larger feeder cables. This makes visual sizing verification fast for both inspectors and crew during rough-in.

Southwire’s 12/3 NM-B is also manufactured in the USA, which matters for buyers who need supply chain assurance, predictable lead times, and the consistent code compliance that domestic manufacturing delivers. The made-in-USA status also makes the Southwire 12/3 NM-B 250 ft eligible for certain federal and state procurement programs that require domestic manufacture.

Southwire 12/3 NM-B 250 ft Specifications

Southwire 12/3 NM-B 250 ft FAQs

Who the Southwire 12/3 NM-B 250 ft Is Built For

The Southwire 12/3 NM-B 250 ft Romex SIMpull is built for two clear buyer types. The first is licensed electrical contractors running residential rough-ins, additions, kitchen and bath remodels, basement finishing projects, and any installation that involves three-way switching, 240V appliance branches, or multi-wire branch circuits. For these buyers, the SIMpull jacket pays for itself in labor savings on every long pull, the 250 foot spool is the right length for typical project consumption, and bulk orders ship with contractor volume pricing applied automatically. Most rough-ins use both 12/2 and 12/3, so contractors typically buy spools of each.

The second buyer is the serious DIY homeowner doing their own permitted electrical work, particularly when the project involves three-way switching upgrades. Adding a three-way switch to control a light from two locations is one of the most common DIY upgrades that genuinely benefits a home, and 12/3 is the cable that makes it possible. For these buyers, the Southwire 12/3 NM-B 250 ft is the same wire your electrician would pull, with no compromise on quality or code compliance. The yellow industry-standard jacket makes inspector approval straightforward.

If your project mixes simple 20-amp circuits with three-way or 240V applications, you will likely need both the Southwire 12/3 NM-B 250 ft and the Southwire 12/2 NM-B 250 ft in your bill of materials. Browse the full IB Lighting electrical wire collection for the complete range of NM-B sizes plus other cable types.

12/3 vs 12/2 Wire: Which Should You Buy?

The Southwire 12/3 NM-B 250 ft and the Southwire 12/2 NM-B 250 ft are siblings in the same Romex SIMpull family. Same 12 AWG solid copper conductors, same SIMpull jacket, same 600V 90C rating, same UL listing, same yellow jacket color. The only difference is the conductor count, and that single difference determines which cable is correct for your application.

Choose 12/3 NM-B if your circuit involves a three-way or four-way switch, a 240V appliance with both hots and neutral, a multi-wire branch circuit with shared neutral, a half-switched receptacle, or any other configuration that genuinely needs three insulated conductors. The Southwire 12/3 NM-B 250 ft is the right pick when 12/2 cannot do the job.

Choose 12/2 NM-B if your circuit is a standard 20-amp single-pole switched lighting branch, a typical receptacle circuit, a kitchen counter outlet served by its own dedicated breaker, or any other configuration with two current-carrying conductors. 12/2 is the most common residential branch wire and is meaningfully less expensive per foot than 12/3.

Most residential projects use both. Contractors typically stock spools of each, plus 14/2 for 15-amp lighting branches. The Southwire 12/2 NM-B 250 ft handles the bulk of branch wiring, and the Southwire 12/3 NM-B 250 ft picks up the three-way and 240V applications.

Installation Tips for the Southwire 12/3 NM-B 250 ft

Pulling 12/3 Romex SIMpull through a residential framing rough-in follows the same fundamentals as 12/2 with a few specific considerations. First, drill all your stud and joist holes before starting any pulls. 12/3 is meaningfully thicker than 12/2, so holes should be sized accordingly. Holes should be at least 1.25 inches from the nearest stud edge to satisfy the NEC nail-plate requirement, and centered through the structural member when possible.

Use cable staples to secure the Southwire 12/3 NM-B 250 ft within 12 inches of every box and at intervals not exceeding 4.5 feet along the run, per NEC code. Do not over-tighten staples or you will crush the cable jacket and risk a code violation. Maintain at least 6 inches of free cable inside every electrical box to give yourself room to work during termination, and consider 8 inches for three-way switch boxes which can get crowded with traveler conductors and wire nuts.

For terminations, strip about 8 to 10 inches of jacket back at each box (more than 12/2 because three-way switch wiring needs more conductor length to manage). Use linesman pliers to make clean wire nut connections, and torque receptacle and switch terminals to manufacturer spec. For three-way switches, label your travelers carefully during rough-in because mixing them up at trim-out leads to nonworking switching that takes meaningful troubleshooting time to resolve. Code requires nail plates over any cable run within 1.25 inches of the stud edge to protect against drywall screws and nails.

Bulk and Contractor Pricing

The Southwire 12/3 NM-B 250 ft is one of IB Lighting’s stocked wire SKUs because contractors buy it alongside 12/2 on most residential rough-ins. We offer automatic volume pricing on multi-spool orders, with deeper savings on larger bills of materials. For a typical residential rough-in covering multiple rooms with three-way switching, a 2 to 5 spool order of 12/3 is common alongside a 5 to 10 spool order of 12/2, and these combined orders trigger our standard contractor pricing tier.

Free freight applies to every Southwire 12/3 NM-B 250 ft 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 THHN, UF, SE, and feeder cables to round out your project bill.

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