NEC Structure, Article 690 Overview, and PV System Classifications

Why the NEC Matters for PV Installers

Every electrical installation in the United States, including solar photovoltaic (PV) systems, must comply with the National Electrical Code (NEC), formally known as NFPA 70. The NEC is published by the National Fire Protection Association and is adopted into law by most states and local jurisdictions. When an authority having jurisdiction (AHJ) — typically a building or electrical inspector — approves your permit and signs off on your inspection, they are confirming that your work meets the NEC. Failing inspection costs time, money, and reputation. More importantly, a non-compliant installation can cause fires, electric shock, or electrocution. The NEC is a safety document first.

How the NEC Is Organized

Understanding the structure of the NEC lets you find answers quickly rather than guessing.

• Chapters 1–7 contain general and specific installation requirements. Chapter 1 (Articles 90–110) covers general rules that apply to everything. Chapters 2–4 build from wiring methods to equipment. Chapters 5–7 cover special occupancies, special equipment, and special conditions.
• Chapter 6 is where PV systems live. Article 690 (PV Systems) is in Chapter 6, which means Article 690 provisions modify or supplement the general rules in Chapters 1–4, but do not replace them unless specifically stated.
• Article 705 (Interconnected Electric Power Production Sources) and Article 706 (Energy Storage Systems) often work alongside Article 690 for grid-tied and battery-storage systems.
• Each article is divided into Parts (Part I, Part II, etc.), then Sections (e.g., 690.4), then subsections (e.g., 690.4(A)).
• The Index at the back of the codebook and the Table of Contents at the front are your two fastest navigation tools. Always confirm the exact part and section before applying a rule.

Article 690 at a Glance

Article 690 is titled Solar Photovoltaic (PV) Systems. It covers the installation of PV systems, including the source circuits, output circuits, disconnecting means, ground-fault and arc-fault protection, system grounding, and marking requirements. The article is divided into numbered parts, each addressing a specific area of the system:

• Part I – General includes scope, definitions (690.2), and general installation requirements.
• Part II – Circuit Requirements covers current and voltage calculations, maximum system voltage, and conductor sizing.
• Part III – Disconnecting Means addresses how and where to install required disconnects.
• Part IV – Wiring Methods specifies acceptable cable types and installation practices.
• Part V – Grounding and Bonding details equipment-grounding conductors and system bonding.
• Part VI – Marking requires labels on equipment, conductors, and disconnects so that first responders and maintenance workers can identify live circuits safely.
• Part VII – Connection to Other Sources (and interaction with Article 705) governs grid-tied and multimode systems.
• Part VIII – Energy Storage Systems (coordinated with Article 706) covers battery-based systems.

When you are working on a job, always start with the definitions in 690.2 to confirm you are using terms the same way the code does.

PV System Classifications

Not all PV systems are the same, and Article 690 applies differently depending on system type. The definitions in 690.2 are authoritative.

Stand-Alone (Off-Grid) Systems supply loads that are not connected to an electric utility. Power comes only from PV modules and, usually, battery storage. There is no grid connection. A remote cabin is a classic example. Stand-alone systems must still meet Article 690 requirements, but Article 705 (interconnection) does not apply.

Interactive (Grid-Tied) Systems are connected to the electric utility in parallel. Excess power can flow back to the grid. These systems require inverters that meet anti-islanding requirements — meaning they automatically shut down if the grid loses power so that utility workers are not endangered by a back-fed line they think is de-energized. Article 705 governs the interconnection. Residential rooftop solar is almost always an interactive system.

Multimode Systems can operate both in parallel with the utility and as stand-alone systems when the grid is unavailable. They use a special multimode inverter or inverter-charger. When grid-tied, Article 705 applies; when operating off-grid, the stand-alone provisions govern. Article 706 applies if battery storage is included.

Direct-Coupled Systems connect a PV source directly to a load (such as a PV water pump) with no battery or inverter. These are simple systems but must still meet applicable sections of Article 690.

Safety Considerations

Before you open the codebook on a real job, remember that PV systems present two serious electrical hazards:

1. PV source circuits are energized by sunlight and cannot be turned off by a switch alone. Always follow lockout/tagout (LOTO) procedures and use appropriate PPE, including arc-rated clothing and insulated gloves rated for the system voltage, before working on any circuit.

2. Back-fed utility voltage is present at the utility-side terminals of an interactive inverter even when the inverter is off. Treat those terminals as always live.

The NEC's marking requirements in Part VI of Article 690 exist precisely so that anyone working on or near the system — including firefighters — can identify energized conductors and disconnecting means quickly. Correct labeling is not optional; it is a life-safety requirement.

Navigating the Codebook Efficiently

Practice a simple three-step routine: (1) Identify the topic — is this a wiring method question, a disconnect question, or a definitions question? (2) Go to the Table of Contents or Index to find the article and part. (3) Read the section and any referenced sections it points to. Many sections cross-reference other articles; follow those references before reaching a conclusion. Speed comes with repetition, which is why locating sections quickly is a skill tested on the NABCEP PV Associate exam.