Quick Overview

250MCM STR PVC/NYLON GRY

THHN Building Wire

THHN building wire is a trusted choice for power distribution and branch circuit wiring across numerous electrical systems. Designed for durability and safety, this copper conductor wire features a PVC insulation layer and a nylon jacket that resists moisture, heat, oil, and abrasion. Known for consistent performance in conduit and cable tray installations, THHN wire is a standard solution for electricians, contractors, and engineers who need dependable wire that meets demanding specifications.

At Interstate Wire Company, we stock and distribute THHN electrical wire from leading manufacturers in the industry. Each spool meets UL and CSA standards to ensure quality and long service life. We offer THHN copper wire for projects of every size.

What Is THHN Wire?

THHN stands for thermoplastic high heat-resistant nylon-coated, a material specification that defines the insulation and jacket type. This construction gives THHN wire its versatility, allowing it to perform reliably in dry and damp locations.

Engineered for conductivity and strength, copper THHN wire offers flexibility during installation and long-term stability under load. Its nylon coating protects against chemicals and physical wear, making it ideal for use in conduits, raceways, and control systems.

THHN Wire Specifications and Construction

THHN building wire delivers performance and longevity in demanding electrical applications while maintaining the flexibility required for conduit or tray installations.

All THHN wire offered by Interstate Wire complies with RoHS and REACH standards. Its voltage rating is typically 600 volts, and its temperature rating is up to 90°C in dry environments or 75°C in wet conditions, depending on application requirements.

Our THHN copper wire provides consistent electrical conductivity and mechanical strength for industrial, commercial, and residential wiring projects. Whether you’re specifying THHN wire for power distribution, control systems, or equipment wiring, each option meets precise THHN wire specifications for safety and reliability.

Quality You Can Trust

Interstate Wire maintains strict quality control standards to ensure every THHN building wire shipment meets customer and regulatory requirements. We source all materials from certified manufacturers and verify them through in-house inspection before distribution.

We employ an ISO 9001-certified quality management system to ensure consistency across every reel and spool. Our compliance with UL, CSA, RoHS, and REACH standards supports safe, environmentally responsible installations and aligns with national and international specifications.

By combining certified products with responsive service and traceable documentation, Interstate Wire gives contractors and engineers confidence that their THHN wire meets the highest standards for safety, performance, and reliability.

Why Choose Interstate Wire for Your THHN Electrical Wire Supply

Interstate Wire combines product availability, technical expertise, and responsive service to support projects of every scale. Our THHN building wire inventory meets the specific requirements of electrical contractors and OEMs. We efficiently handle large-volume orders and long-term supply programs to ensure reliable delivery schedules for repeat customers.

Our team works directly with purchasing and engineering departments to confirm that each THHN copper wire selection meets project specifications and installation codes. With accurate documentation and fast turnaround, Interstate Wire helps simplify procurement for electrical distributors and end users alike. Whether you need standard stock lengths or custom wire preparation services, our focus remains the same: providing quality wire and consistent support to keep your operations moving.

Request a Quote for THHN Building Wire

Get the wire you need when you need it. Contact Interstate Wire to request pricing and availability for the THHN building wire your project requires. Our team will provide detailed specifications, lead times and documentation to help you plan confidently.

Frequently Asked Questions

What is THHN wire suitable for?

THHN wire is suitable for power distribution, branch circuit wiring, and control applications in commercial, industrial, and residential environments. Common uses include lighting, appliance circuits, and building wiring systems where durable insulation and reliable conductivity are essential.

Can THHN wire be buried in conduit?

THHN building wire can be installed underground if it is run inside a watertight conduit. The nylon jacket and PVC insulation provide strong protection against moisture and abrasion, but a conduit is essential.

Can you use THHN wire for automotive applications?

THHN wire is not recommended for automotive use. Automotive projects typically require GPT, TXL, or GXL wire, which meet SAE standards for vehicle wiring.