If you’re working on electrical projects in your home or business, you’ve probably heard of THHN and THWN wire. These are some of the most common types of building wire used today.
But what does THHN/THWN wire meaning actually mean? And what’s the difference between THHN and THWN? We’ll break it down in this article. We’ll also take a look at other common types of wire like XHHW and Romex, so you can make the right choice for your project.
Understanding THHN wire
THHN stands for Thermoplastic High Heat-resistant Nylon-coated wire. Let’s break that down:
- Thermoplastic: The insulation is made of a plastic that softens when heated.
- High Heat-resistant: This wire can withstand high temperatures.
- Nylon-coated: A nylon coating provides added protection against abrasion, oil, and chemicals.
THHN wire is rated to handle temperatures up to 90°C (194°F) in dry locations and up to 75°C (167°F) in wet locations.
Common uses for THHN wire
You’ll often find THHN wire in:
- General wiring in buildings
- Conduits and cable trays
- Control circuits
Exploring THWN wire
THWN is an acronym that describes a specific type of insulated electrical wire. Let’s break down what each letter means:
- T stands for thermoplastic, the type of insulation used.
- H means the wire is heat resistant.
- W indicates that the wire is water resistant.
- N means the wire is nylon coated.
THWN wire has a temperature rating of up to 90°C (194°F) in dry locations and up to 75°C (167°F) in wet locations.
Where THWN wire shines
Because of its water-resistant properties, THWN wire is ideal for:
- Areas where the wire might be exposed to water
- Wet and damp locations
- Use in conduit, especially underground
THHN vs. THWN: What are the key differences?
The main difference between THHN and THWN wiring is their water resistance. THWN has better water resistance than THHN.
The temperature ratings are the same for both types of wire in both wet and dry environments:
- THHN: 90°C (dry), 75°C (wet)
- THWN: 90°C (dry), 75°C (wet)
When should you use each type of wire? Use THWN wiring for damp and wet environments. You can use THHN wiring in dry environments, but you can also substitute THWN wiring.
What about XHHW and XHHW-2 wire?
You might also run across XHHW and XHHW-2 wire, so it’s a good idea to know what those markings mean.
XHHW Wire
XHHW stands for cross-linked polyethylene high heat-resistant water-resistant wire. The insulation is made of cross-linked polyethylene (XLPE), and this wire is temperature-rated to 90°C in both wet and dry locations.
XHHW-2 Wire
XHHW-2 wire is an improved version of XHHW wire. It’s temperature-rated up to 150°C in dry locations and 90°C in wet locations.
Applications
You can use XHHW wire for power distribution and in high-temperature locations. XHHW-2 wire is often used in commercial and industrial applications.
Frequently Asked Questions
What is the difference between THHN and THWN wire?
While both THHN and THWN wires are commonly used in electrical wiring, the key difference lies in their intended environments. THHN stands for Thermoplastic High Heat-resistant Nylon-coated. THWN, on the other hand, stands for Thermoplastic Heat and Water-resistant Nylon-coated. Essentially, THWN wire is designed to withstand both heat and moisture, making it suitable for damp or wet locations, while THHN is intended for dry locations. Some wires are dual-rated as THHN/THWN, offering versatility for various applications.
Does THHN wire need conduit?
Whether or not THHN wire needs conduit depends on the specific application and local electrical codes. In many residential and commercial installations, THHN wire is typically run inside conduit for added protection. Conduit provides a physical barrier against damage, moisture, and other environmental factors. However, in some cases, THHN wire can be used without conduit, such as when it’s installed inside cable trays or raceways specifically designed for open wiring. Always consult local electrical codes and regulations to ensure compliance and safety.
Putting It All Together
THHN, THWN, and XHHW wires have slightly different properties, so make sure you select the right wire for your specific project. When choosing, don’t forget to consider the environmental conditions where you’ll be running the wire. Temperature and moisture both play a role in wire selection.
Finally, always check your local electrical codes. Following the codes ensures your work will be up to par and pass inspection.