What Is NEC Article 690? Definition & Guide

Key Takeaways

Article 690 is the primary NEC section governing solar PV system installation
Covers circuit sizing, overcurrent protection, disconnects, grounding, and labeling
690.12 rapid shutdown requirements have become increasingly stringent since the 2017 code cycle
Wire sizing must account for 125% of continuous current (Isc for PV source circuits)
Updated every three years as part of the NEC revision cycle
Solar designers must understand Article 690 to produce code-compliant permit packages

What Is NEC Article 690?

NEC Article 690 — titled “Solar Photovoltaic (PV) Systems” — is the section of the National Electrical Code that establishes safety requirements for the design, installation, and inspection of solar PV systems. It covers everything from conductor sizing and overcurrent protection to grounding, disconnecting means, labeling, and rapid shutdown.

Article 690 applies to all PV systems that produce power for premises wiring systems, whether residential, commercial, or utility-scale. It works alongside other NEC articles (particularly Article 705 for interconnection) and is adopted by most U.S. jurisdictions as the basis for solar permitting and inspection.

Every plan set produced by solar design software must demonstrate compliance with Article 690. Inspectors check conductor sizing, overcurrent protection, grounding methods, disconnect locations, and rapid shutdown compliance — all drawn directly from this article.

How Article 690 Is Organized

Article 690 is divided into parts that address different aspects of PV system installation:

Part I — General

Defines scope, terms, and the relationship between Article 690 and other NEC articles. Establishes that PV source circuits, PV output circuits, and inverter output circuits each have distinct requirements.

Part II — Circuit Requirements

Covers conductor sizing (690.8), overcurrent protection (690.9), and stand-alone system requirements. The 125% continuous current factor for PV circuits is established here.

III

Part III — Disconnecting Means

Specifies requirements for PV system disconnects, including location, accessibility, grouping, and labeling. Each energy source must have a clearly marked disconnect.

Part IV — Wiring Methods

Addresses acceptable wiring methods for PV systems, including requirements for PV wire (USE-2, PV Wire), conduit fill, and routing through buildings. Rooftop wiring has specific requirements for securing and protecting conductors.

Part V — Grounding and Bonding

Details equipment grounding conductor sizing, grounding electrode requirements, and the distinction between grounded and ungrounded PV systems. Module frame grounding and racking bonding are covered here.

Part VI — Labeling and Marking

Requires specific labels on PV systems including source identification, voltage warnings, rapid shutdown indicators, and arc-flash hazard labels. Label content and placement are defined in detail.

Key Sections of Article 690

Several sections within Article 690 are particularly critical for solar professionals:

Circuit Sizing

690.8 — Circuit Sizing and Current

Requires PV source circuit conductors to be sized for 125% of the short-circuit current (Isc) of the module string. This accounts for irradiance values exceeding standard test conditions and ensures conductors can safely handle continuous PV output.

Safety Critical

690.12 — Rapid Shutdown

Requires PV systems on buildings to reduce conductor voltage to 80V or less within 30 seconds of rapid shutdown initiation. The 2020 NEC requires module-level shutdown capability. This drives the use of MLPEs (microinverters or DC optimizers).

Protection

690.9 — Overcurrent Protection

Defines when and how overcurrent protection devices (fuses or breakers) must be applied to PV source and output circuits. Series-connected strings with three or more parallel sources require individual string fusing.

Grounding

690.41–690.47 — Grounding

Covers system grounding (functional grounding of one conductor) and equipment grounding (safety grounding of exposed metal parts). Permits both grounded and ungrounded PV array configurations with specific requirements for each.

Designer’s Note

The rapid shutdown requirements in 690.12 are the most frequently evolving section of Article 690. Before designing any system, confirm which NEC edition your local jurisdiction has adopted — the 2014, 2017, 2020, and 2023 versions all have different rapid shutdown requirements.

Key Metrics & Calculations

Article 690 establishes specific calculation requirements that solar designers must apply:

Calculation	NEC Section	Formula / Requirement
Maximum Circuit Current	690.8(A)	Isc × 1.25
Conductor Ampacity	690.8(B)	Must exceed maximum circuit current × temperature correction × conduit fill
Maximum System Voltage	690.7	Voc × temperature correction factor (lowest expected temp)
Overcurrent Device Rating	690.9	Must be ≥ 125% of maximum circuit current
Ground Fault Protection	690.41	Required for grounded DC systems over 5 kW
Rapid Shutdown Voltage	690.12	Under 80V within 30 seconds, under 1V within 30 seconds (2020+)

Conductor Sizing Formula

Required Ampacity = Isc × 1.25 × 1.25 / (Temp Correction × Conduit Fill Factor)

The double 1.25 factor accounts for continuous load (first 1.25) and conductor ampacity derating (second 1.25), though the 2017+ NEC consolidated this into a single 1.25 factor applied differently.

Practical Guidance

Article 690 compliance affects every role in the solar workflow:

Know which NEC edition applies. Your AHJ (Authority Having Jurisdiction) may be on the 2017, 2020, or 2023 NEC. The rapid shutdown and grounding requirements differ significantly between editions. Designing to the wrong code version causes permit rejections.
Use module-level shutdown equipment. To comply with 690.12 in jurisdictions on the 2017+ NEC, specify microinverters or DC optimizers with listed rapid shutdown capability. Solar design software should verify MLPE compatibility.
Calculate maximum voltage at lowest temperature. String voltage at the coldest expected temperature must not exceed the inverter’s maximum input voltage or the conductor/equipment voltage ratings. Use the temperature coefficients from module datasheets.
Include all required labels on plan sets. Permit reviewers look for specific labels including DC disconnect, AC disconnect, rapid shutdown initiation device, point of interconnection, and voltage/current warnings.

Verify conductor sizing on site. Confirm that installed wire gauges match the approved plan set. Using undersized conductors is the most common 690 violation found during inspections.
Install all required disconnects. Every energy source (PV array, battery, grid) needs its own clearly labeled disconnect that is accessible to first responders and utility personnel.
Test rapid shutdown before final inspection. Demonstrate that the rapid shutdown system works by activating the initiator and verifying voltage drops within the required timeframes using a voltmeter.
Apply labels before the inspector arrives. Missing or incorrect labels are the easiest thing for an inspector to flag. Pre-print labels based on the approved plan set and install them during construction.

Understand rapid shutdown cost implications. Module-level electronics required by 690.12 add cost but also provide panel-level monitoring and optimization. Position these as benefits, not just compliance costs.
Explain safety features to homeowners. Customers appreciate knowing their system includes rapid shutdown for firefighter safety, proper grounding, and code-compliant wiring. It builds confidence in the installation quality.
Factor permit timelines into project schedules. Complex 690 compliance documentation can extend permit review times. Set realistic timelines with customers, especially in jurisdictions with strict plan review processes.
Differentiate on code expertise. Many competitors produce non-compliant designs that fail inspection. Emphasize that your team’s solar design software and NEC knowledge means fewer permit delays and inspection failures.

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Real-World Examples

Residential: Rapid Shutdown Compliance

A solar installer in New York designed a 10 kW rooftop system using string inverters. The local jurisdiction had adopted the 2020 NEC, requiring module-level rapid shutdown per 690.12. The installer switched to DC power optimizers on each module, adding $1,200 to the system cost but achieving compliance. The system passed inspection on the first visit.

Commercial: Overcurrent Protection Design

A 150 kW commercial rooftop system required careful attention to 690.9 overcurrent protection. With 12 parallel strings feeding a central inverter, each string required individual fuse protection. The designer specified 15A fuses based on the module’s Isc of 10.5A (10.5 × 1.25 = 13.1A, next standard fuse size = 15A). Proper fuse sizing prevented a potential string fault from becoming a fire hazard.

Permit Rejection: Voltage Calculation Error

A residential system in Minnesota was rejected during permit review because the designer failed to calculate maximum voltage at the record low temperature of -35°F. The 12-module string exceeded the inverter’s 600V maximum input voltage at that temperature. The designer had to reduce the string length to 10 modules and resubmit the plan set, delaying the project by three weeks.

Impact on System Design

Article 690 requirements directly influence design decisions in solar software workflows:

Design Decision	NEC 690 Requirement	Impact
String Length	690.7 — Max voltage at coldest temp	Limits modules per string
Wire Gauge	690.8 — 125% of Isc	Often requires #10 AWG minimum for residential
Fuse Selection	690.9 — Series fuse rating	Must be between 125% Isc and module max series fuse rating
Rapid Shutdown	690.12 — Module-level shutdown	Requires MLPEs on building-mounted systems
Disconnect Location	690.13 — Accessible disconnect	Must be within sight of inverter or lockable

Pro Tip

Keep a reference table of temperature correction factors from NEC Table 690.7(A) for your region. The voltage correction factor at -40°C is 1.18 for crystalline silicon — a module with Voc of 49.5V at STC reaches 58.4V at extreme cold, which can push a long string over inverter limits.

Frequently Asked Questions

What does NEC Article 690 cover?

NEC Article 690 covers the electrical safety requirements for solar photovoltaic systems. This includes circuit sizing and conductor requirements, overcurrent protection, disconnecting means, wiring methods, grounding and bonding, rapid shutdown, marking and labeling, and connection to other sources. It applies to all PV systems connected to premises wiring.

What is the NEC 690.12 rapid shutdown requirement?

NEC 690.12 requires PV systems on buildings to rapidly reduce DC conductor voltage when initiated by a shutdown device (typically located at the main service panel). Under the 2020 NEC, conductors within the array boundary must drop to 80V or less within 30 seconds and to 1V or less within 30 seconds of module-level shutdown. This requirement exists to protect firefighters and first responders from electrocution hazards on rooftops.

How do you size wires according to NEC 690?

Under NEC 690.8, PV source circuit conductors must have an ampacity of at least 125% of the maximum circuit current (which is the module’s Isc for source circuits). You then apply temperature correction factors and conduit fill adjustment factors. The conductor must be rated for the maximum system voltage as calculated at the lowest expected ambient temperature per 690.7. Most residential PV source circuits use #10 AWG copper minimum.

What NEC edition should I design to?

Always design to the NEC edition adopted by your local Authority Having Jurisdiction (AHJ). This varies by city, county, and state. Some jurisdictions are still on the 2017 NEC, many have adopted the 2020 NEC, and some have moved to the 2023 NEC. Contact your local building department or check their website to confirm the adopted code edition before starting any design.