What is the maximum voltage rating for THHN and THWN conductors?

The maximum voltage rating for THHN (Thermoplastic High Heat-resistant Nylon-coated) and THWN (Thermoplastic Heat and Water-resistant Nylon-coated) conductors is 600 volts. This rating is established by the National Electrical Code (NEC) and indicates the highest voltage that these particular types of conductors can safely handle without risk of insulation breakdown or failure.

THHN and THWN wire are designed for both residential and commercial use, making them suitable for various applications, including power distribution and equipment wiring. Their 600-volt rating allows for broad versatility, enabling them to be used in different environments and installations where reliable performance at this voltage level is required.

Other voltage ratings mentioned, such as 300 volts, 450 volts, or 750 volts, are not applicable to THHN and THWN conductors. The 600-volt rating serves as an important standard in electrical work, ensuring safety and compliance.