When it comes to electrical wiring, choosing the right type of wire is critical for safety, efficiency, and durability. Two of the most commonly used building wires are THHN and THW - but what exactly do these letters mean, and how do they differ?
In this guide, we'll break down the differences between THHN and THW wire, helping you make the best decision for your electrical project - whether it's industrial, residential, or commercial.
What Does THW Wire Mean?
THW stands for Thermoplastic Heat and Water-resistant wire.
It is designed to perform well in wet or damp environments, such as outdoor conduits, water treatment facilities, or underground installations.
Key Characteristics of THW Wire:
- T – Thermoplastic insulation
- H – Heat resistant (up to 75°C)
- W – Water resistant
THW wires are typically thicker and have an additional insulation layer to prevent moisture penetration. This makes them ideal for moisture-prone areas and harsh environments where humidity or water exposure is a concern.
What Does THHN Wire Mean?
THHN stands for Thermoplastic High Heat-resistant Nylon-coated wire.
This type of wire is widely used in dry and indoor applications due to its nylon coating, which provides abrasion resistance and durability during installation.
Key Characteristics of THHN Wire:
- T – Thermoplastic insulation
- H – High heat resistant (up to 90°C in dry locations)
- H – (second H) means higher temperature rating
- N – Nylon jacket for mechanical protection
THHN wires are thinner, lightweight, and easier to pull through conduits - making them popular for industrial buildings, control panels, and machine wiring.
Key Differences Between THHN and THW Wire
| Feature | THHN Wire | THW Wire |
|---|---|---|
| Full Name | Thermoplastic High Heat-resistant Nylon-coated | Thermoplastic Heat and Water-resistant |
| Insulation Type | Thermoplastic with Nylon coating | Thermoplastic with water-resistant insulation |
| Temperature Rating | Up to 90°C (dry) | Up to 75°C (wet or dry) |
| Water Resistance | Limited (for dry areas only) | Excellent (suitable for wet locations) |
| Flexibility | Higher due to thinner insulation | Thicker insulation, slightly less flexible |
| Application | Indoor, dry locations, control wiring | Outdoor, wet or underground environments |
| Durability | Great for mechanical protection (nylon jacket) | Great for moisture and corrosion protection |
| Cost | Slightly lower | Slightly higher due to added protection |
In short, THHN is the best option for dry, indoor environments, while THW is preferred for wet or outdoor applications.
How to Choose Between THHN and THW Wire
Choosing between THHN and THW wire depends largely on the installation environment and safety requirements.
Case 1: Industrial Factory Wiring
An electronics manufacturing plant required wiring for their indoor control panels.
→ Recommended: THHN wire, because of its high heat resistance and easy installation in conduit systems.
Result: Reduced labor time and improved wiring efficiency.
Case 2: Outdoor Pump System
A construction project needed cabling for a water pump system installed underground and constantly exposed to moisture.
→ Recommended: THW wire, for its superior water resistance and insulation thickness.
Result: Long-term reliability and reduced maintenance costs.
Why Choose Dongguan Greater Wire & Cable Co., Ltd.
At Dongguan Greater Wire & Cable Co., Ltd., we specialize in high-quality THW Wire, manufactured to international safety and performance standards.
Our products feature excellent insulation durability, high conductivity, and superior water resistance, making them ideal for construction, industrial, and power distribution projects of all sizes.
No matter the scale of your project, we provide:
- Comprehensive pre-sale and after-sale technical support
- Customized cable solutions tailored to your needs
- Competitive pricing with global delivery
Let our professional team help you find the right cable solution today!
📞 Tel/WhatsApp/Wechat: +86 135 1078 4550 / +86 136 6257 9592
📧 Email: manager01@greaterwire.com
🌐 Dongguan Greater Wire & Cable Co., Ltd.