Understanding NEC Article 690: Solar Photovoltaic (PV) Systems

NEC Article 690 provides comprehensive safety and installation standards for photovoltaic (PV) systems, which convert sunlight into electrical energy. These systems are increasingly popular for residential, commercial, and utility-scale applications. Article 690 covers standalone and interactive systems, ensuring compliance with essential safety and performance requirements.

Scope of Article 690

This article applies to:

• Solar PV systems, including array circuits, inverters, controllers, and associated wiring.
• Systems with alternating current (AC) or direct current (DC) outputs.
• Both standalone and grid-interactive installations.

Exclusions: Large-scale PV electric supply stations (covered under Article 691).

Key Requirements for PV Systems

1. General Installation Requirements (690.4)
   • Qualified Personnel: Only trained professionals can perform PV system installations.
   • Multiple Systems: Multiple PV systems on the same structure must include directories for disconnecting means as per Article 705.10.
   • Floating PV Equipment: Systems on water must be suitable for humidity, corrosion, and structural stresses.
2. Circuit Requirements (690.7, 690.8)
   • Maximum Voltage: PV system DC circuits in residential installations are limited to 600 volts; commercial systems can reach 1000 volts.
   • Conductor Sizing: Calculations must factor in maximum current and continuous load requirements.
3. Overcurrent Protection (690.9)
   • All circuits require overcurrent protection unless conductors have sufficient ampacity to handle the maximum current safely.
4. Arc-Fault and Ground-Fault Protection (690.11, 690.41)
   • Systems with DC circuits above 80 volts must include arc-fault protection to reduce fire risks.
   • Ground-fault protection is required for circuits over 30 volts or 8 amperes.
5. Rapid Shutdown Requirements (690.12)
   • PV systems on buildings must include a rapid shutdown feature to reduce voltage for firefighter safety during emergencies.
6. Disconnecting Means (690.13, 690.15)
   • Systems must have accessible disconnecting means to isolate PV circuits and equipment.
7. Wiring and Material Specifications (690.31)
   • PV wiring must be suitable for wet, outdoor, and high-temperature conditions.
   • Metal raceways or enclosures are required for circuits over 30 volts inside buildings.
8. Grounding and Bonding (690.41, 690.43)
   • Equipment and conductor enclosures must be bonded to a grounding conductor for safety.
   • Ground-fault detection interrupters are required to minimize fire hazards.

Applications

NEC Article 690 supports safe installation and operation of:

• Residential PV Systems: Rooftop solar panels for homes.
• Commercial Installations: Large-scale systems for business facilities.
• Utility-Scale Projects: Ground-mounted systems generating substantial electricity for grids.

Conclusion

NEC Article 690 ensures safe and efficient use of photovoltaic systems by addressing circuit design, grounding, disconnecting means, and rapid shutdown for emergency safety. These standards provide a reliable framework for the growing adoption of solar energy.