THW wire (also known as THW cable) is one of the most common and versatile wires in Thai electrical work. Knowing its characteristics, uses, and how to size it correctly helps you get a safe, cost-effective installation. This comprehensive guide covers THW wire from top to bottom.
What Is THW Wire?
THW is copper wire with PVC insulation, rated for 450/750V at 70°C. Electricians often call it “single wire” or “round wire.” It offers heat and moisture resistance, making it suitable for both indoor and outdoor applications.
Main Advantages of THW
- Durable, with good heat and humidity resistance.
- Flexible and easy to install.
- Reasonably priced for the quality.
- Available in a wide range of sizes.
Common Applications
- Overhead installation on electrical poles.
- Indoor wiring in homes and offices.
- Conduit installation above ceilings.
- Power supply for industrial equipment.
- High-moisture environments.
THW Wire Sizing Guide
THW comes in a broad range of sizes and current ratings. As a reference, the smallest and largest common sizes are:
| Size | Current capacity |
|---|---|
| THW 1×1.5 mm² | from ~21 A |
| THW 1×400 mm² | up to ~736 A |
Smaller sizes suit residential circuits, while the larger sizes are used for industrial loads.
How to Choose the Right Size
Select the wire size based on the equipment’s wattage. For example, THW 1×2.5 mm² suits appliances up to about 3,500 watts, while larger sizes are needed for industrial machinery. Always size the wire to the load with a safety margin to prevent overheating.
Buy Standard THW Wire from TETA Intertrade
TETA Intertrade is a wire-wholesale specialist supplying TIS-standard THW copper wire in every common size for home, office, and industrial use. We help you choose the right size for your load — safe, durable, and correctly rated.
Frequently Asked Questions (FAQs)
What is THW wire rated for?
THW is copper wire with PVC insulation rated for 450/750V at a maximum operating temperature of 70°C, with heat and moisture resistance suitable for indoor and outdoor use.
What size THW wire should I use for a 3,500-watt appliance?
THW 1×2.5 mm² is suitable for appliances up to about 3,500 watts. For higher loads or industrial machinery, step up to a larger size, always sizing to the actual load.
Can THW wire be used outdoors?
Yes. THW’s heat and moisture resistance makes it suitable for outdoor applications such as overhead pole runs, as well as indoor wiring and conduit above ceilings.
What’s the range of THW wire sizes?
THW is available from small residential sizes like 1×1.5 mm² (around 21 A) up to large industrial sizes like 1×400 mm² (around 736 A).
