In the realm of 600V, 90°C rated electrical cables, RHW-2 and USE-2 are both common specifications that can sometimes cause confusion. While they share similar temperature ratings, they are governed by different standards and engineered for distinct primary applications. The fundamental difference is this: RHW-2 is a versatile, general-purpose building wire designed for installation within raceways, while USE-2 is a specialized service entrance cable built to be directly buried or exposed to harsh outdoor elements. Choosing incorrectly can lead to code violations or premature failure. This guide clarifies their definitions, standards, and ideal use cases.
Core Definitions & Governing Standards
Understanding the foundational identity of each cable is crucial for proper selection.
1.RHW-2 (Rubber Heat & Water Resistant -2):
- Standard: Governed by UL 44, the standard for Thermoplastic-Insulated Wires . It is classified as a general-purpose building wire.
- Core Identity: A moisture and heat-resistant wire suitable for use in both dry and wet locations. The “-2” suffix indicates its 90°C rating in wet conditions. It is commonly insulated with XLPE (Cross-linked Polyethylene) or a thermoset rubber like EPR/CPE and may have an additional protective jacket . Its design assumes installation within a protective enclosure like conduit or cable tray.
2.USE-2 (Underground Service Entrance -2):
- Standard: Governed by UL 854, the standard for Service-Entrance Cables .
- Core Identity: A specialized cable for underground service entrance and direct burial applications. It is often triple-listed as RHH/RHW-2/USE-2. Its construction typically features a single, thick layer of XLPE insulation that acts as both the insulator and the rugged outer jacket, with no separate sheath . This monolithic design is formulated to withstand direct contact with soil, moisture, and sunlight.
Key Differences: A Side-by-Side Comparison
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Feature
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RHW-2 Wire
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USE-2 Cable
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|---|---|---|
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Full Name
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Rubber, Heat & Water-resistant -2
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Underground Service Entrance -2
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Governing Standard
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UL 44 (Building Wire)
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UL 854 (Service-Entrance Cable)
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Voltage Rating
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600V, 1000V, or 2000V
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600V
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Construction
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XLPE or Thermoset Insulation, may have a separate jacket.
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Single, thick, weather-resistant XLPE layer (No separate jacket; insulation is the jacket) .
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Direct Burial Suitability
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Permissible in some cases, but not its primary design purpose. Less resistant to soil crushing and puncture.
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Inherently Designed & Certified for Direct Burial. The robust XLPE is formulated to resist soil pressure, moisture, and corrosion .
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UV / Sunlight Resistance
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Good, but not necessarily optimized for long-term, unprotected exposure.
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Excellent. Specifically compounded for long-term outdoor exposure without conduit .
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Primary Installation Method
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Inside Conduit, Raceway, Cable Tray (Indoor/Wet Locations)
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Direct Burial, Exposed Outdoor Runs, within Conduit
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Moisture/Water Resistance
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Rated for wet locations (90°C wet) .
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Superior, with enhanced hydrolysis resistance for constant soil or water contact.
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Typical Applications
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General building wiring in conduit for feeders, branch circuits, industrial controls .
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Underground Service Drops, Solar PV DC Circuits (NEC 690), Direct Burial Feeders, exposed outdoor feeders .
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Conductor Material
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Primarily Copper
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Copper or Aluminum (Aluminum is very common for cost-effective service entrance) .
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Flame Rating
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Typically rated for VW-1 flame test .
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Typically rated for VW-1 flame test.
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Detailed Application Scenarios: Where Each One Excels
1.When to Use RHW-2: The Versatile Conduit Wire
RHW-2 is the go-to choice for a wide range of protected wiring applications where the cable is installed inside conduit, electrical metallic tubing (EMT), or other approved raceways. Its design balances cost, flexibility, and performance for indoor and outdoor (when in conduit) use.
- Commercial/Industrial/Residential Wiring: For feeders and branch circuits inside walls, ceilings, and concrete slabs where conduit is required.
- Industrial Control Panels and Machine Tool Wiring.
- Wet Location Conduit Runs: Such as in parking garages, laundries, or outdoor locations where the cable is fully protected within the raceway.
2.When to Use USE-2: The Direct Burial & Outdoor Specialist
USE-2 is purpose-built for harsh, unprotected environments and is the code-specified choice for many outdoor-to-indoor transition points.
- Direct Burial Service Entrance: The underground run from the utility transformer to a building’s meter base.
- Photovoltaic (PV) Systems: It is specifically recognized and required by NEC Article 690 for the DC circuit wiring between solar panels and to the combiner box or inverter .
- Exposed Outdoor Feeders: For supplying power to detached garages, pumps, or landscape lighting where conduit burial is not desired.
- Areas with High Moisture or Corrosive Soil: Its enhanced insulation provides long-term reliability.
Conclusion: Making the Right Choice for Safety and Code Compliance
The decision is guided by one primary factor: Will the cable be permanently protected inside a raceway, or will it be in direct contact with earth, sunlight, and weather?
- Choose RHW-2 for reliable, cost-effective in-conduit wiring throughout buildings and industrial facilities. It is the standard workhorse for protected installations.
- Choose USE-2 when you need a cable for direct burial, exposed outdoor PV arrays, or as an underground service entrance. Its construction is not an upgrade—it’s a fundamental requirement for these demanding applications. Never substitute a general-purpose building wire (RHW-2) for a direct burial service cable (USE-2) in an exposed or buried application.
JZD Cable supplies certified RHW-2 for your conduit projects and robust, NEC-compliant USE-2 for your outdoor, burial, and solar applications. Contact us today to discuss your specifications or visit jzdcable.com to explore our product range.
