400 MCM THHN/THWN-2 Copper Building Wire | Stranded 600V

"The heavy-duty choice for high-amperage industrial power—engineered with dual-rated THHN/THWN-2 insulation and a friction-reducing nylon jacket for maximum reliability in 600V applications."

Why Electricians Choose 400 MCM THHN/THWN-2 Copper

The 400 MCM copper building wire is a high-capacity conductor designed for major power distribution systems. It is the primary choice for 335-amp industrial feeders, large-scale motor control centers, and critical commercial infrastructure. Our advanced stranded construction is essential at this massive size, ensuring consistent electrical performance and superior durability within large equipment enclosures.

• 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 large-diameter conduits.

• High-Conductivity Copper: Manufactured with soft-annealed stranded copper to provide maximum flexibility and superior electrical conductivity for heavy feeders.

• Oil & Gasoline Resistant: The specialized jacket is designed to resist chemical degradation, making it ideal for industrial environments, refineries, and service stations.

Common 400 MCM THHN/THWN-2 Applications

• Industrial Main Feeders: The primary power source for large factories and manufacturing plants.

• Commercial Main Services: Used in single or parallel sets for buildings with high power density requirements, like industrial laundries or data hubs.

• Industrial Transformer Feeders: Ideal for the primary or secondary side of mid-to-large step-down transformers.

• Large HVAC Plants: Providing dedicated power to massive chillers and industrial refrigeration racks.

• Renewable Energy Infrastructure: Connecting high-output solar inverters to commercial-scale distribution panels.

Technical Specifications

ENGINEERING OVERVIEW: 400 MCM STR 600V

• APPLICATION: Industrial service entrance conductors, heavy feeders, and large-scale 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:  335 amps at 75°C | 380 amps at 90°C 

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.

General Shipping Information

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 Shipping

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).

Returns

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.