How to Properly Label a PV System per NEC 690 (Marking & Identification)

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), these requirements appear throughout Article 690 (including rapid-shutdown and disconnecting-mean provisions) with related power-source identification centralized in Article 705. Key areas of focus include the photovoltaic system disconnecting means, the rapid shutdown switch, and all enclosures containing DC conductors. The 2023 NEC centralizes many multi-source identification requirements in Article 705. 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 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 Article 690 contains the PV-specific marking rules (for example, 690.12 for rapid shutdown, 690.13 for PV disconnecting means, and 690.31 for wiring identification), Article 705 centralizes identification for multiple power sources at the service equipment location. The 2023 NEC consolidated some multi-source identification language into 705.10 to make it easier to find premises-level plaques and directories. 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). NEC also requires a permanent, readily visible label indicating the highest maximum DC voltage in the PV system (calculated in accordance with 690.7) at one of specified locations (for example, the DC PV system disconnecting means). Other electrical values needed for conductor sizing and protection are set out elsewhere in Article 690 (such as 690.7 for voltage calculations and 690.8 for current calculations) and by equipment listing or manufacturer instructions. If the disconnect’s line and load terminals can be energized in the open position, a caution/warning label is required to indicate that terminals may be energized.

Rapid Shutdown Switch (RSD)

For firefighter safety, the rapid shutdown switch is one of the most critical labels. NEC 690.12 requires a permanent label at each service equipment location to indicate that the “SOLAR PV SYSTEM IS EQUIPPED WITH RAPID SHUTDOWN” and to show the location of the initiation device. The initiation device (switch or breaker) must be labeled to indicate its role; the code prescribes minimum lettering, coloring, and visibility requirements (see 690.12 for the specific label wording and location rules). For additional guidance on implementing these marking changes in the 2023 NEC, see how to comply with all service equipment labeling.

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(D)(2) requires that exposed raceways, cable trays, and other wiring methods containing PV DC conductors be marked with wording such as “PHOTOVOLTAIC POWER SOURCE” or “SOLAR PV DC CIRCUIT” by means of permanently affixed labels. Labels must be visible after installation, appear on every separated section, use capitalized letters with a minimum height, and provide clear contrast (for example, white letters on a red background). Spacing between labels shall not exceed 3 m (10 ft), and labels must be placed at points where the conduit enters or emerges from walls or enclosures.

Point of Interconnection (POI)

Where the PV system connects to the utility grid, often via a back-fed breaker, specific markings are mandatory. NEC 705.10 centralizes the requirements for identifying power sources: a permanent plaque, label, or directory shall be installed at each service equipment location (or at an approved readily visible location) to identify the location of each power source disconnecting means and to display emergency contact numbers for off-site entities that service the systems. 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 Article 690 and Article 705.
2. Calculate and Verify Electrical Data: Determine the precise values for maximum system voltage and maximum circuit currents. The maximum DC voltage must be calculated per 690.7 and marked where required; maximum circuit current calculations for conductor sizing and overcurrent protection are covered by 690.8 and related tables. 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), field-applied markings must have sufficient durability and be permanently affixed (not handwritten). 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 are consistent with common safety-sign conventions described in the ANSI Z535 family of standards for safety signs. These standards help with signal words (DANGER, WARNING, CAUTION), colors, 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 a critical requirement under NEC 110.16 where equipment is likely to require examination, adjustment, servicing, or maintenance while energized. These labels warn qualified persons of potential arc flash hazards and help identify required PPE. While many residential installations do not meet the criteria for arc-flash labeling, the final determination should be made by a qualified person evaluating the specific installation and per 110.16. Separately, the concept of electrical safety relies on more than just labels. Proper system bonding—connecting metallic, non-current-carrying parts to provide a safe fault-current path—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 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 the required label spacing on a long conduit run. Be methodical when labeling all raceways containing hazardous DC conductors; spacing between markings must not exceed 3 m (10 ft) where required.
• 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 among 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?

Residential PV systems often do not require an arc flash hazard label because NEC 110.16 applies to equipment likely to require servicing while energized; the requirement depends on the specific installation and whether personnel will need to work on energized equipment. A qualified person should evaluate the system and determine whether arc-flash labeling is required.

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

Per NEC 690.31(D)(2), raceways, cable trays, and other wiring methods that contain PV DC conductors must be identified with wording such as “PHOTOVOLTAIC POWER SOURCE” or “SOLAR PV DC CIRCUIT.” The marking must be permanent, visible after installation, have capitalized letters of the minimum size specified, and contrast the background (commonly white letters on red). Spacing between markings shall not exceed 3 m (10 ft), and labels must be applied where conduits enter or leave enclosures or walls.

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 (affecting calculated maximum circuit current and short-circuit current used for conductor sizing and protection). Those calculated values must be accurately reflected where required by the NEC and equipment listing instructions.

Primary Sources

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