How to Properly Label a PV System per NEC 690 Part VI

Proper solar PV system labeling is a non-negotiable aspect of any safe and compliant installation. For a master or journeyman electrician, correctly applying these labels is crucial for passing inspection and ensuring the long-term safety of first responders and maintenance personnel. Governed by the National Electrical Code (NEC), specifically NEC 690 Part VI, these requirements detail the specific warnings, diagrams, and electrical data that must be displayed. Key areas of focus include the photovoltaic system disconnecting means, the rapid shutdown switch, and all enclosures containing DC conductors. The 2023 NEC has further refined these rules, consolidating many power source identification requirements into Article 705.10 to create a more unified standard. Adhering to these marking and labeling guidelines, including those for arc flash hazards and back-fed breakers, is fundamental to professional electrician training and practice.

The Critical Role of Solar PV System Labeling for Safety and Compliance

For any licensed electrician, from a newly certified journeyman electrician to a seasoned master electrician, understanding the nuances of solar PV system labeling is essential. These labels are not just a bureaucratic hurdle; they are a critical safety communication tool. In an emergency, firefighters need to quickly identify how to de-energize a building. A properly labeled rapid shutdown switch and photovoltaic system disconnecting means can be the difference between a controlled situation and a catastrophe. These requirements are outlined in NFPA 70, more commonly known as the NEC. Failure to comply can result in failed inspections, costly rework, and most importantly, a dangerous environment for anyone interacting with the system.

Understanding NEC 690 Part VI and 705.10: The Foundation of PV Labeling

The core requirements for marking solar installations are found in the NEC code book, primarily within Article 690. While Part VI of Article 690 is titled “Marking,” it’s crucial to know that recent code cycles have consolidated some rules. The 2023 NEC, for instance, moved many general requirements for identifying interconnected power sources to NEC 705.10. This change streamlines the code, making it easier for installers to find all relevant plaque and directory rules in one place. These sections dictate the language, colors, and locations for labels that identify hazards and provide essential system information. For a deeper look at recent updates, electricians can explore online electrical courses that break down how equipment marking requirements have changed in the 2023 NEC.

Key Labeling Locations and Requirements

A comprehensive solar PV system labeling strategy involves placing specific, durable labels at multiple key points throughout the installation.

Photovoltaic System Disconnecting Means

Every DC and AC disconnect needs clear identification. Per NEC 690.13(B), each PV system disconnect must be permanently marked “PV SYSTEM DISCONNECT” or equivalent and plainly indicate whether it is open (off) or closed (on). Furthermore, labels at the DC disconnect must state the rated maximum power-point voltage (Vmpp), rated maximum power-point current (Impp), maximum system voltage, and short-circuit current, as required by NEC 690.53. If the system includes a charge controller or dc-to-dc converter, the label must also include its maximum rated output current. If the disconnect’s line and load sides can be energized in the open position, an “ELECTRICAL SHOCK HAZARD” warning is also required. These detailed markings are similar to those required for other service equipment, and understanding how to comply with all service equipment labeling is a hallmark of a professional installation.

Rapid Shutdown Switch (RSD)

For firefighter safety, the rapid shutdown switch is one of the most critical labels. Per NEC 690.56(C), a permanent plaque must be installed at the service equipment and the shutdown initiator location stating: “SOLAR PV SYSTEM IS EQUIPPED WITH RAPID SHUTDOWN”. The initiation device itself, if a switch or breaker, requires a separate label with the words “PV SYSTEM RAPID SHUTDOWN INITIATION DEVICE.” These labels must be reflective, with capitalized letters on a red background. Additionally, a placard at the main service disconnect must show the location of the rapid shutdown initiator and may include a diagram indicating which parts of the PV system remain energized after shutdown.

Conduit, Raceways, and Enclosures with DC Conductors

Anywhere that DC conductors are present, they must be clearly identified to prevent a dangerous electrical shock hazard. NEC 690.31(G)(4) requires that exposed raceways, junction boxes, and conduit bodies containing PV DC circuits be marked with the words “WARNING: PHOTOVOLTAIC POWER SOURCE”. These labels must be placed at intervals of no more than 10 feet. The code specifies capitalized white letters on a red background for maximum visibility. Proper conduit labeling is one of the most common issues flagged during inspections.

Point of Interconnection (POI)

Where the PV system connects to the utility grid, often via a back-fed breaker, specific labels are mandatory. NEC 705.10 now centralizes the requirements for marking power sources. A permanent plaque or directory must be installed at the service equipment location denoting all power sources on the premises and the location of their disconnecting means. The 2023 NEC adds a requirement to include emergency contact numbers for any off-site companies that service the system, aligning the code with NFPA 1 (Fire Code). Mastering these interconnection rules is just as important as knowing how to properly label switchgear and panelboards in general.

Step-by-Step Guide to Creating Compliant PV Labels

Ensuring every label is correct and properly placed can feel complex. Following a methodical process helps guarantee compliance and safety.

1. Identify All Required Labeling Locations: Walk through your project plans and the physical site. Systematically identify every disconnect (AC and DC), inverter, combiner box, conduit run, junction box, and the main service panel where a label is needed per NEC 690 and 705.
2. Calculate and Verify Electrical Data: Determine the precise values for maximum system voltage, rated maximum power-point current, and short-circuit current. These figures are calculated based on the PV module specifications and how they are wired (e.g., in a series vs parallel circuit). Double-check your calculations before printing labels.
3. Select Durable, Code-Compliant Materials: Labels must be “suitable for the environment,” which means they must resist fading from UV exposure and withstand temperature fluctuations and moisture. Per NEC 110.21(B), markings must have sufficient durability. Pre-printed, engraved phenolic, or UV-stable polyester labels are common professional choices.
4. Follow ANSI Z535 Standards for Formatting: The NEC’s color and text requirements align with the ANSI Z535 family of standards for safety signs. These standards dictate the use of signal words (like DANGER, WARNING, CAUTION), colors (red for DANGER, orange for WARNING), and symbols to create universally understood safety messages.
5. Affix Labels Securely and Visibly: Labels must be permanently affixed and clearly visible to anyone servicing or inspecting the equipment. Do not place labels where they can be easily obscured or on removable covers that might be misplaced.

Special Considerations: Arc Flash and Bonding

For commercial and large-scale PV systems, arc flash hazard labels are another critical requirement under NEC 110.16. These labels warn qualified persons of potential arc flash hazards and specify the necessary personal protective equipment (PPE). While less common on standard residential systems, any equipment likely to require examination or service while energized must be evaluated. Separately, the concept of electrical safety relies on more than just labels. Proper system bonding—what is it? It’s the process of connecting all metallic, non-current-carrying components of the system together to create a safe path for fault current to travel, which is essential for grounding and overall system safety. A well-labeled and properly bonded system represents the highest standard of electrical work.

Common Mistakes and How to Avoid Them

Even experienced electricians can miss a detail. Passing inspection the first time requires avoiding these common pitfalls.

• Using Improper Materials: Handwritten or paper labels are not acceptable. They fade and deteriorate, quickly becoming illegible. Always use professionally made, weather-resistant labels.
• Incorrect Placement: A label on the wrong disconnect or hidden behind a pipe is useless. Ensure every label is placed exactly where the code specifies and is easy to read.
• Outdated or Inaccurate Information: Using values from a different project or failing to perform correct voltage and current calculations will lead to a failed inspection.
• Forgetting Conduit Labels: It is easy to miss a 10-foot interval on a long conduit run. Be methodical when labeling all raceways containing hazardous high voltage DC conductors.
• Ignoring the Point of Interconnection: The plaque identifying multiple power sources at the service disconnect is one of the most important for utility and emergency personnel.

Don’t let a simple sticker hold up your project. Pass inspection the first time. Get our complete PV labeling checklist.

Frequently Asked Questions (FAQ)

What is the most important label for a solar PV system?

While all labels are important for compliance, the rapid shutdown switch label and the plaque indicating multiple power sources at the service disconnect are arguably the most critical for life safety. They provide essential, immediate information to firefighters and utility workers during an emergency.

Do I need an arc flash hazard label on a residential PV system?

Typically, residential PV systems do not require an arc flash hazard label because the equipment is not likely to be examined or serviced while energized. However, this requirement (NEC 110.16) applies to any electrical equipment that might be, so the final determination depends on the specific system and service plan. The decision should be made by a qualified person performing an arc flash risk assessment.

What are the requirements for conduit labeling for PV DC conductors?

According to NEC 690.31(G)(4), any raceway or conduit containing DC conductors from a photovoltaic source must be marked with the words “WARNING: PHOTOVOLTAIC POWER SOURCE”. The labels must have capitalized white text on a red background and be placed at intervals not exceeding 10 feet, as well as at points where the conduit is entered or emerges from walls or enclosures.

How does solar PV system labeling change for series vs parallel circuit configurations?

The label requirements themselves don’t change based on circuit design, but the electrical data on the labels will. A series vs parallel circuit configuration directly impacts the system’s electrical characteristics. Connecting modules in series increases the maximum system voltage, while connecting them in parallel increases the current (both rated maximum power-point current and short-circuit current). These calculated values must be accurately reflected on the labels at the photovoltaic system disconnecting means.

Primary Sources

• NFPA 70, National Electrical Code (NEC), 2023 Edition
• ANSI Z535 Series – Standards for Safety Signs and Colors