What is UL 5107? The Standard for MG High-Temperature Lead Wire

What is UL 5107?

In severe industrial environments, heat is the ultimate enemy of electrical infrastructure. When operating temperatures surpass the limits of standard thermoplastic or silicone insulations—such as inside blast furnaces, commercial ovens, or heavy-duty heating elements—standard hook-up wire will rapidly melt, crack, and fail.

To handle these extreme thermal conditions, engineers and procurement managers specify UL Style 5107 wire. Commonly known in the field as Type MG (Mica-Glass) wire, this single-conductor appliance lead wire is specifically engineered to maintain electrical integrity where other cables literally burn up.

Understanding the structural standards governed by UL 5107 is essential for selecting the correct high-temperature lead wire for your facility.

Image above is an example of a UL 5107 12 AWG MG High-Temp Wire. 

The Definition: What is the UL 5107 Standard?

UL Style 5107 is a technical design standard established by Underwriters Laboratories under the Appliance Wiring Material (AWM) category. It specifically regulates single-conductor hook-up and lead wire rated for continuous operating temperatures up to 450°C (842°F) and a voltage ceiling of 600 Volts.

Cables certified under UL 5107 are authorized for the internal wiring of high-temperature commercial, industrial, and household electrical equipment. However, the standard specifies a critical physical constraint: the wire must be deployed in static applications where it is protected from mechanical damage and not subjected to continuous, repeated flexing.

Structural Anatomy of a UL 5107 Cable

Achieving a 450°C continuous thermal rating requires removing standard plastics and synthetics entirely from the manufacturing process. Under UL 5107 guidelines, the cable must be constructed using distinct high-grade materials:

The Conductor (Nickel-Plated or Nickel-Clad): Standard bare copper oxidizes rapidly at high temperatures. UL 5107 wires feature high-flex stranded conductors made of 27% nickel-coated copper or nickel-clad copper to resist oxidation and thermal scaling.

1. The Primary Insulation (Mica Tape): The core conductor is wrapped in multiple layers of premium mica composite tape. Mica is a naturally occurring mineral sheet with incredible dielectric strength and a melting point well above 1,000°C, providing the primary electrical insulation.

2. The Outer Jacket (Fiberglass Braid): To hold the mica layers intact and offer abrasion resistance, an overall fiberglass braid is woven over the insulation. This braid is treated with a high-temperature finish (typically a PTFE or silicone saturant) to prevent fraying during installation.

Primary Applications for UL 5107 Wire

Because of its extreme heat threshold, you will find UL 5107 MG wire serving as critical internal lead wire across several heavy industrial sectors:

• Industrial Processing & Refineries: Internal wiring for ceramic kilns, glass manufacturing plants, blast furnaces, and iron/steel mill machinery.

• Commercial Food Service: Powering the internal heating loops of commercial bakery ovens, industrial deep fryers, and high-temp food processing equipment.

• Heater Elements: Direct termination leads for industrial band heaters, cartridge heaters, and strip heating manifolds.

• Aerospace & Power Generation: Sensor lines, boiler control panels, and exhaust monitor infrastructure where ambient heat destroys traditional electronics.

Key Technical Specifications to Verify

When sourcing UL 5107 wire for your project, ensure your submittals align with these verified metrics:

• Voltage Rating: 600 Volts alternating current (VAC).

• Temperature Spectrum: Rated for continuous service at 450°C (842°F). (Note: Non-UL peaks can occasionally reach up to 538°C for brief durations).

• Flame Resistance: Must pass standard industry horizontal and vertical flame testing.

• Environmental Resistance: Highly resistant to moisture, chemical solvents, oils, and ozone exposure.

How Wire America Support Your High-Temp Wire Sourcing.

Wire America is an agile partner for all types of high-temperature wire.  We supply a comprehensive line of Type MG 450°C wire built to full UL 5107 and UL 5335 specifications across a wide range of AWG sizes - from 18 AWG to 4/0. We provide flexible, custom cut-to-length service so you can order the exact footage your maintenance cycle or machine build requires. Backed by rapid nationwide fulfillment, we ensure you get the exact materials you need without excessive warehouse overhead.

Need to replace high-temperature lead wire in your facility? Contact the Wire America team today at 833-268-8644  or email your specifications directly to sales@wireamerica.com.

Click Here to Shop Our MG 450°C | 550°C High Temp Wire Selection

At Wire America, we believe in genuine conversation. You'll always talk with real people who understand that every project requires careful product selection. We're here to ensure you feel educated, confident, and great about your final purchase.  We supply several different types of High Temperature Wire such as MG Wire, TGGT, SRML, SIS, UL 1330, SRG-K, and many more.  Feel free to give us a call to discuss your project! You can reach us at: 833-268-8644 or email sales@wireamerica.com

⚠️ Important Disclaimer: Safety and Compliance

Wire America provides this information as a guide only. Electrical installations must strictly adhere to the National Electrical Code (NEC) and all state, local, and jurisdictional requirements, which vary widely. Always consult a licensed electrician, electrical engineer, or the local inspecting authority before purchasing material or starting any electrical project. Wire America assumes no liability for the installation, use, or interpretation of these guides.