Installation

NEC 690

NEC 690 is the article within the National Electrical Code (NEC) that governs the installation of solar photovoltaic systems in the United States. Published by the National Fire Protection Association (NFPA), it covers every aspect of solar electrical installation from conductor sizing and overcurrent protection to grounding, disconnects, rapid shutdown, and fire safety setbacks.

Key NEC 690 requirements that affect residential solar installations include: maximum system voltage limits (typically 600V DC for residential), conductor ampacity calculations based on continuous current ratings (125% of Isc), equipment grounding of all metal components, ground-fault protection for all systems, disconnecting means accessible to emergency responders, rapid shutdown compliance, and wire management specifications.

NEC 690 is updated on a three-year cycle along with the rest of the National Electrical Code. The 2017 edition introduced stringent rapid shutdown requirements. The 2020 edition expanded module-level rapid shutdown and added requirements for energy storage systems. The 2023 edition refined arc-fault detection and added provisions for newer technologies like bifacial panels and DC-coupled storage.

Local jurisdictions adopt specific NEC editions — some areas enforce the 2020 code while others have adopted 2023. The applicable code depends on when and where the system is installed. Building departments and electrical inspectors enforce NEC 690 during the permitting and inspection process.

DIY solar installers must understand NEC 690 thoroughly or work with a licensed electrician for the electrical portions of the installation. Violations of NEC 690 can result in failed inspections, denied interconnection, voided insurance coverage, and genuine safety hazards including fire and electrocution risk.

Frequently Asked Questions

Do I need to know NEC 690 to install my own solar?

If you plan to DIY, you should understand the basics of NEC 690 — especially conductor sizing, overcurrent protection, grounding, and rapid shutdown requirements. Many jurisdictions require a licensed electrician to perform or supervise the electrical connections even on DIY installations. The electrical inspection will verify NEC 690 compliance regardless of who did the work.

Does NEC 690 apply to off-grid systems?

NEC 690 applies to all photovoltaic systems, including off-grid installations. While some requirements (like utility interconnection rules) only apply to grid-tied systems, the core safety provisions for wiring, grounding, overcurrent protection, and equipment standards apply to all solar installations regardless of grid connection status.