What are the temperature ratings for Type THWN insulation and Type THWN-2 insulation respectively?

Type THWN insulation is rated for a maximum conductor temperature of 75°C, while Type THWN-2 insulation is rated for a maximum conductor temperature of 90°C. This distinction is crucial for applications where the thermal performance of wiring is a significant factor, particularly in environments where higher temperatures may be encountered.

Type THWN insulation is designed to withstand moisture, providing insulation for wet and dry locations with adequate resistance to heat, chemicals, and sunlight. The 75°C rating indicates that the maximum operating temperature under continuous load for conductors insulated with Type THWN should not exceed this limit to ensure safety and longevity of the wire.

On the other hand, Type THWN-2 insulation builds upon the THWN rating by allowing for greater thermal resistance, evidenced by its higher 90°C maximum operating temperature. This is particularly beneficial in applications where higher temperatures are prevalent or where multiple conductors may be installed together, leading to increased heat buildup.

Understanding these temperature ratings is vital for professionals working with electrical installations to ensure the proper selection of wires according to the applications and environments they will be used in, thereby promoting safety and reliability.