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Thhn Vs Thwn

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When it comes to electrical wire, there are many different types available. Two common types of wire used in residential and commercial applications are THHN and THWN. While they may look similar, they have different characteristics and uses. In this article, we will explore the differences between THHN and THWN and their respective applications.

What is THHN?

THHN stands for Thermoplastic High Heat-resistant Nylon-coated. As the name suggests, THHN is a type of wire that is coated with nylon and is able to withstand high temperatures. It is also resistant to oil and gasoline, making it ideal for use in automotive applications.

What is THWN?

THWN stands for Thermoplastic Heat and Water-resistant Nylon-coated. Similar to THHN, it is coated with nylon, but it also has a layer of thermoplastic insulation that makes it resistant to water. This makes it ideal for use in outdoor applications where it may be exposed to the elements.

Differences between THHN and THWN

Characteristic THHN THWN
Temperature Rating 90°C 75°C
Water Resistance No Yes
Applications Indoor, dry locations Outdoor, wet locations
Conductor Material Copper or aluminum Copper only
Insulation Material Polyvinyl chloride (PVC) Thermoplastic
Thickness of Insulation Thin Thick

Applications of THHN and THWN

THHN is typically used in dry indoor locations where it may be exposed to high temperatures or corrosive materials. It is commonly used for wiring motors, transformers, and other industrial equipment. It is also frequently used in automotive applications due to its resistance to oil and gasoline.

THWN, on the other hand, is designed for outdoor use in wet locations. It is commonly used in underground installations, outdoor lighting fixtures, and pool and spa wiring. Its water-resistant properties make it ideal for use in areas that are exposed to moisture.


While THHN and THWN may look similar, they have distinct characteristics that make them suitable for different applications. Choosing the right type of wire is important to ensure the safety and functionality of electrical systems. By understanding the differences between THHN and THWN, you can make an informed decision when selecting wire for your next project.

Published On: 2023年6月16日Categories: ,