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Solid THHN/THWN-2 WireFrom $0.20/ft -
Solid THHN/THWN-2 WireFrom $0.20/ft - Solid THHN/THWN-2 WireFrom $0.20/ft
- Solid THHN/THWN-2 WireFrom $0.20/ft
Parent SKU : THN350CST
SKU : THN350CST-250-BK
"The industrial powerhouse for main service entrances—engineered with dual-rated THHN/THWN-2 insulation and a friction-reducing nylon jacket for maximum reliability in 600V applications."
Why Electricians Choose 350 MCM THHN/THWN-2 Copper The 350 MCM copper building wire is a massive conductor designed for the most demanding electrical loads. It is a go-to for 400-amp services (when paralleled) or single 310-amp industrial feeders. At this gauge, the friction-reducing nylon jacket is a critical feature, allowing these heavy conductors to slide through large-diameter conduits with significantly less resistance.
Dual Rated (THHN/THWN-2): Engineered for dry locations up to 90°C (THHN) and wet locations (THWN-2), providing maximum versatility for indoor and outdoor conduits.
Tough PVC/Nylon Jacket: The high-heat and moisture-resistant PVC insulation is protected by a tough, friction-reducing Nylon outer sheath, making for easier pulls through tight bends.
High-Conductivity Copper: Manufactured with soft-annealed stranded copper to provide maximum flexibility and superior electrical conductivity for branch circuits and feeders.
Oil & Gasoline Resistant: The specialized jacket is designed to resist chemical degradation, making it ideal for industrial environments and service station wiring.
300-Amp Feeders: The primary conductor for supplying high-amperage power to large commercial distribution boards and sub-panels.
Industrial Switchgear: Connecting the main utility transformer to a building's primary distribution switchgear or motor control centers.
Major HVAC Chillers: Providing the massive power required for commercial rooftop units (RTUs) and high-rise refrigeration systems.
Data Center Power Mains: Used in parallel sets to provide reliable, high-conductivity power to massive server farms and UPS systems.
High-Rise Utility Rises: The go-to size for vertical power distribution in multi-story office buildings and luxury apartments.
ENGINEERING OVERVIEW: 350 MCM STR THHN 600V
APPLICATION: Feeder wire for sub-panels, large appliances, and industrial power distribution.
VOLTAGE: Rated for 600 Volts.
CONDUCTORS: Stranded soft-annealed copper.
INSULATION: Heat and moisture-resistant PVC (Polyvinyl Chloride).
JACKET: Tough, abrasion-resistant Nylon.
TEMPERATURE: 90°C Dry (THHN), 90°C Wet (THWN-2).
Ampacity: 310 amps at 75°C | 350 amps at 90°CÂ
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Technical Note: All values are nominal and subject to industry tolerances and manufacturer corrections. Specifications are subject to change without notice. It is the buyer’s responsibility to verify that all materials meet the specific requirements of the project and comply with local electrical codes.
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| Wire Size (AWG/MCM) | 350 MCM |
| Conductor Material | Copper |
| Conductor Type | Stranded |
| Strand Count | 37 |
| Outer Diameter (OD) (in/mm) | 0.830 in. / 21.082 mm |
| Conductor Count | 1 |
| Shield | Unshielded |
| Insulation Type | (THHN) Thermoplastic High Heat-Resistant Nylon-coated |
| UL Listing Numbers | UL 83, UL 1063, UL 758 |
| Voltage Rating | 600V |
| Ampacity Rating | 350 |
| Submersible | No |
| Standards | UL 83 UL VW-1 Size 1/0 & larger suitable for cable tray use MTW per UL 1063 ASTM B1, B3, B8 Federal Spec A-A-59561 |
| Miscellaneous Information | All values are nominal and subject to correction. *90°C Wet/Dry Per NEC Table 310.15 (B)(16) for not more than three conductors in raceway based on 30°C ambient temperature. |
| Primary Applications | General-purpose electrical wiring in commercial, industrial, and residential structures. It's widely used to supply power to outlets, switches, lighting fixtures, and other electrical loads throughout a building |
| Weight per Foot | 1.165 lb |
In-stock orders placed before 3pm EST typically ship within 1-2 business days. Our business days are Monday through Friday; we do not process orders on Saturday, Sunday, or major US Holidays.
You will receive an e-mail with a tracking number within 1-2 business days from the time its shipped. You will also be able to view your order status and tracking numbers in your account order history.
Expedited shipments are delivered Monday-Friday except on US Holidays. The order must be placed before 12pm CST to ship same day ( Mon-Fri Only).
You have 30 days from the day you receive the item to contact us for a return. Returns are subject to a 30% Restocking Fee.
Please contact us at help@wireamerica.com to request a return authorization. Have your order number or name the order was placed with ready and we will email you an RMA (return) number and instructions for return. Currently, we do not offer exchanges. A new order must be placed if you need a different item. If you provide the new order number at the time of your return request, the restocking fee may be lowered.
Orders on any items with a material value of $50 or less are non-returnable.
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Physical Specifications
Technical Specifications
Usage & Installation:
Packaging & Dimensions:
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350 MCM Copper is rated for 350 Amps at 90°C. However, standard commercial equipment and breaker terminations are almost always limited to 75°C, which sets the allowable ampacity at 310 Amps. This makes it the standard choice for 300-amp circuits. We always recommend confirming wire size and local code requirements with a licensed electrician or project engineer before purchasing.
For a standard 4-wire configuration (three phases and a neutral), a 3-inch conduit is the recommended minimum. Because of the weight and stiffness of 350 MCM, using a 3-inch pipe ensures you meet NEC fill requirements while allowing enough space for a safe, lubricated pull.
Note on Conduit Sizing: These recommendations are based on standard NEC 40% fill guidelines for general informational purposes. Always consult with a licensed electrician or project engineer to verify final conduit specifications and gauge size.
Not as a single conductor. At the standard 75°C rating, 350 MCM is rated for 310 Amps. To achieve a 400-amp rating, it is standard industry practice to run two 250 MCM or two 3/0 AWG conductors in parallel per phase. If you specifically prefer 350 MCM, running it in parallel provides even greater capacity and safety margins for 600A+ systems.
No. Like all THHN/THWN-2 products, 350 MCM must be installed in conduit (such as Schedule 40 PVC or Rigid Metal Conduit) for all underground applications. For burial without conduit, you must use a cable rated for direct burial, such as Type USE-2 or Aluminum URD.
The primary advantages are space efficiency and conductivity. 350 MCM Copper carries roughly the same amperage as 500 MCM Aluminum but has a significantly smaller diameter. This allows you to use smaller conduit and provides more room inside switchgear enclosures to "train" the wire into position, which is critical in tight commercial electrical rooms.
350 MCM Copper is very heavy, weighing approximately 1.16 lbs per foot. Because of this weight, we recommend using mechanical tuggers and high-capacity reel stands for installation. Ensure your pull-points and junction boxes are rated for the tension required to pull this gauge.
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