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The main differences between XHHW, XHHW-2, and THHN cables (or wire) lie in the type of insulation, temperature rating, and applications. Here's a detailed comparison:
1. XHHW Cable (X-Low Smoke, Heat-resistant, Water-resistant)
Insulation: Made from cross-linked polyethylene (XLPE). This insulation material is heat-resistant, water-resistant, and offers low smoke emissions when exposed to fire.
Temperature Rating: Typically rated for 90°C (194°F) in both wet and dry conditions.
Applications: XHHW is often used for power distribution, control wiring, and exposed or underground installations in residential, commercial, and industrial applications. It's commonly found in conduit systems.
2. XHHW-2 Cable (X-Low Smoke, Heat-resistant, Water-resistant – Enhanced)
Insulation: Also made from cross-linked polyethylene (XLPE), but XHHW-2 generally offers more enhanced performance compared to the standard XHHW version, particularly in terms of fire resistance, chemical resistance, and durability.
Temperature Rating: Like XHHW, it’s also rated for 90°C (194°F), but it can handle more demanding environmental conditions.
Applications: Similar to XHHW, but XHHW-2 is more commonly used where better chemical resistance and fire-resistance are required. It’s ideal for underground and wet conditions.
3. THHN Wire (Thermoplastic High Heat-resistant Nylon-coated)
Insulation: THHN insulation is made from thermoplastic materials, usually nylon over a PVC (polyvinyl chloride) layer. The outer coating is a nylon jacket, providing good abrasion resistance and some chemical resistance.
Temperature Rating: THHN wire is typically rated for 90°C (194°F) in dry locations and 75°C (167°F) in wet locations. It’s important to note that THHN is generally not suitable for use in wet conditions unless it's specifically marked as THWN (Thermoplastic Heat and Water-resistant Nylon-coated).
Applications: THHN is commonly used for dry locations like inside buildings, conduit systems, and in applications requiring general power and control wiring. It’s often seen in commercial, industrial, and residential settings but not typically used in wet or underground installations unless it's dual-rated as THWN.
Feature | XHHW | XHHW-2 | THHN |
Insulation | Cross-linked polyethylene (XLPE) | Cross-linked polyethylene (XLPE) | Thermoplastic with nylon coating |
Temperature Ratin | 90°C (194°F) in wet or dry | 90°C (194°F) in wet or dry | 90°C (194°F) in dry, 75°C (167°F) in wet |
Application | Power distribution control,wiring conduit | Power distribution, control wiring, improved chemical & fire resistance | Power wiring in dry locations, conduit |
Fire Resistance | Moderate | Improved (better fire resistance) | Moderate, but less than XHHW-2 |
Chemical | Good | Better (more resistant to harsh environment | Moderate to low |
Resistance | chemicals) | (depends on application) | |
Moisture Resistance | Good | Good | Low (not suitable for wet locations unless THWN) |
Usage Environment | Wet and dry locations | Wet and dry locations | Primarily dry locations (or wet if dual-rated THWN) |
Summary of Applications:
XHHW is suitable for both wet and dry environments, ideal for power distribution and control in conduit, especially when moisture and heat are factors.
XHHW-2 is essentially a more enhanced version of XHHW, offering better chemical resistance, higher fire resistance, and greater durability, making it suitable for more demanding environments.
THHN is typically used for dry environments, and if rated THWN, it can be used in wet locations. It is commonly found in commercial, residential, and industrial applications for general power wiring but lacks the moisture and chemical resistance of XHHW cables.
In conclusion:
XHHW and XHHW-2 are more suitable for moisture-prone and outdoor environments.
THHN is best for indoor, dry locations, and general power wiring where moisture isn't a concern (unless THWN is specified for wet use).