Ⅰ. Definition and Standards

• RHH: Rubber-insulated, heat-resistant, and moisture-resistant cable

• RHW-2: Heat-resistant, wet-location cable (rated for higher temperatures than RHW)

Ⅱ. Key Structural Components

2.1 Conductor Details

• Material: Oxygen-free copper (solid or stranded)

• Solid core: Suitable for fixed installations (e.g., #10, #8 AWG)

• Stranded core: Enhances flexibility for movable setups (e.g., #12, #14 AWG)

• Cross-Sectional Area:

• Common sizes: 14AWG (2.5 mm²) to 6AWG (16 mm²)

• Stranding: 19 strands for stranded conductors (e.g., #10 AWG: 19×0.254 mm)

2.2 Insulation Layer

• Material: Cross-linked polyethylene (XLPE)

• Cross-linking method: Silane or electron beam (EB) curing

• Thickness:

• 0.76 mm (14AWG) to 1.14 mm (6AWG)

• Key Properties:

• Thermal stability: -40°C to +90°C (RHW-2: up to +90°C in wet locations)

• Electrical strength: ≥20 kV/mm breakdown voltage

Ⅲ. Electrical and Environmental Specifications

Ⅳ. Comparison: Single Layer vs. Double Layer PV Cables

Ⅴ. Certification and Compliance

• UL 4703: Mandatory for PV applications in North America, specifying:

• Temperature cycling (-40°C to +90°C, 1000 cycles)

• Impact resistance at -30°C

• NEC 2023 (Article 690): Requires:

• Grounding of non-current-carrying conductors

• Separation from other circuits in conduit

• RoHS Compliance: Lead-free conductor and halogen-free insulation (optional for some markets)

Ⅵ. Applications and Limitations

6.1 Ideal Use Cases

• Residential Indoor Wiring: Between inverters and electrical panels

• Conduit Systems: Underground or wall-mounted runs with physical protection

• Off-Grid Cabin Setups: Dry environments with minimal UV exposure

• Temporary PV Installations: Short-term projects requiring cost-effective wiring

6.2 Limitations

• Not Suitable for:

• Direct outdoor exposure (without conduit)

• High-moisture environments (e.g., coastal areas)

• Applications requiring flame retardancy beyond VW-1 rating

• Moveable or vibrating systems (stranded cables preferred)

Ⅶ. Installation and Handling Tips

1. Termination:

• Use UL-listed crimp terminals (e.g., ring terminals for solid core)

• Avoid over-crimping, which may damage XLPE insulation.

2. Conduit Selection:

• PVC conduit for outdoor buried runs (UV protection)

• Metal conduit for fire-rated installations

3. Temperature Derating:

• At 40°C ambient, derate current by 80% (NEC Table 310.15(B)(2)(a))

4. Grounding:

• If using green-insulated ground wires, ensure compliance with NEC 250.118

Ⅷ. Maintenance and Longevity

• Aging Prevention:

• Avoid prolonged exposure to sunlight (use conduit or UV-stabilized XLPE)

• Monitor for cracking in high-temperature areas (e.g., near inverters)

• Expected Lifespan:

• 10–15 years in protected environments

• 5–8 years in unprotected outdoor setups (without UV additives)

• Testing Recommendations:

• Periodic insulation resistance tests (≥100MΩ at 500V DC)