From $0.20/ft
128 Products
-
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 : THN250CST
SKU : THN250CST-250-BK
The heavy-weight standard for industrial power distribution and main service entrances—engineered with dual-rated THHN/THWN-2 insulation and a friction-reducing nylon jacket for maximum reliability in 600V applications.
The 250 MCM copper building wire is a high-capacity conductor designed for the most demanding electrical loads. It is a primary choice for 250-amp commercial services, large industrial motor control centers, and main distribution switchgear. At this massive size, our stranded construction is a necessity, providing the flexibility required to "train" the wire into large enclosures and land it securely in high-torque mechanical lugs.
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.
Industrial Main Feeders: The primary power source for large factories and manufacturing plants.
Commercial Switchgear: Connecting the main utility transformer to the building's main distribution switchgear.
Large-Scale HVAC: Powering massive chiller plants and industrial cooling towers.
Hospital Power Systems: Used in critical power distribution for healthcare facilities.
ENGINEERING OVERVIEW: 250 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: 255 amps at 75°C | 290 amps at 90°CÂ
Â
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.
Â
| Wire Size (AWG/MCM) | 250 MCM |
| Conductor Material | Copper |
| Conductor Type | Stranded |
| Strand Count | 37 |
| Outer Diameter (OD) (in/mm) | 0.720 in. / 18.288 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 | 290 |
| 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-59559 |
| 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 | 0.845 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.
Get notified when this product is back in stock
Physical Specifications
Technical Specifications
Usage & Installation:
Packaging & Dimensions:
|
||||||||||||||||||||||||||||||||
MCM stands for Thousand Circular Mils (1,000 Circular Mils). It is a unit of measure used for wires larger than 4/0 AWG. The larger the MCM number, the thicker the wire and the more electricity it can safely carry.
250 MCM THHN copper wire is rated for 290 Amps at 90°C. When following the NEC 75°C column (the standard for most heavy-duty industrial breakers and terminals), the allowable ampacity is 255 Amps. This makes it the go-to choice for 250-amp main feeders and industrial service entrances. Always consult with a local electrician on the exact size for your project.
A 2.5-inch conduit is the minimum standard for up to three 250 MCM conductors. If you are pulling a 4-wire system (three phases plus a neutral), a 3-inch conduit is highly recommended to stay within the NEC 40% fill limit. Using a 3-inch pipe will significantly reduce the risk of "jamming" and lower the pulling tension required for such a heavy cable.
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.
Yes, as long as it is installed in a protective conduit. The THWN-2 rating ensures the insulation is engineered for wet locations, making it suitable for underground PVC or rigid metal conduit systems where water may be present. It is not rated for direct burial; for that, you would need specialized cable like Type USE-2 or Aluminum URD.
Absolutely. It is very common to run multiple 250 MCM conductors in parallel to achieve 500-Amp or 1,000-Amp service ratings, as smaller parallel wires are often easier to pull than one massive 1000 MCM cable.
It comes down to efficiency and space. Because copper has superior electrical conductivity, 250 MCM Copper can carry the same amount of power as 350 MCM Aluminum but with a much smaller physical footprint.
(833) 268-8644
Get this thing filled up so you can help Wire America!