NEC Article 690 Complete Guide: Every Section Explained for Solar Installers

NEC Article 690 is the national electrical code standard for solar photovoltaic systems in the United States. Every grid-tied and off-grid solar installation — from a 3 kW residential rooftop to a 500 kW commercial ground mount — must comply with its requirements.

This guide covers every major section of Article 690, explains what each requires, and provides the practical compliance information that solar designers and installers need for AHJ submissions.

Article 690 Structure Overview

NEC Article 690 is organized into parts covering different aspects of PV system installation:

Part I: General — 690.1 to 690.4

690.1: Scope

Article 690 covers electrical installations for solar PV systems, including the equipment and wiring for such systems. It applies to standalone, utility-interactive, and multi-mode systems.

690.2: Definitions

Key defined terms used throughout Article 690:

• PV Source Circuit: Conductors between modules and the first overcurrent protection or inverter input
• PV Output Circuit: Conductors between the PV overcurrent protection device and the inverter
• Array: Complete PV system assembly including modules, mounting, wiring, and inverter
• Interactive System: PV system connected to and operating in parallel with an electric utility

690.4: Installation

All PV system equipment must be listed (UL, ETL, CSA, or other recognized listing organization) and installed per its listing and labeling. Equipment not specifically designed and listed for PV use (e.g., standard AC wire used in DC circuits) is not permitted.

Part II: Circuit Requirements

690.7: Maximum Voltage

The most commonly checked section at plan review. The rule:

Temperature Correction: The voltage used is the worst-case open-circuit voltage corrected for the lowest expected ambient temperature at the site. The ASHRAE Extreme Annual Mean Minimum Design Dry Bulb Temperature is the standard reference.

Voc_max = Voc_STC × N_series × [1 + (T_min - 25°C) × (β_Voc/100)]

See the full NEC 690.7 guide for detailed calculation examples.

690.8: Circuit Current

Minimum conductor ampacity = 125% × maximum circuit current

• Source circuit: Isc of one string (modules in series don’t add current)
• Output circuit: Sum of all parallel string Isc values

After the 125% factor, apply standard ampacity derating for ambient temperature and conduit fill. For rooftop conduit, add 22°C to the ambient temperature per NEC 310.15(B)(3)(c).

See the full NEC 690.8 guide for derating examples.

690.9: Overcurrent Protection

Every PV source circuit conductor and PV output circuit conductor must be protected by an overcurrent device (fuse or breaker) rated for:

• Minimum: 125% × maximum circuit current (same calculation as 690.8)
• DC rating: The OCPD must be rated for DC operation at the system voltage — standard AC breakers are NOT rated for DC and cannot be used in PV source or output circuits
• PV-listed equipment: Combiner box fuses and string inverter input protection must be listed for PV use

Part III: Disconnecting Means

690.12: Rapid Shutdown

All building-mounted PV systems must include a rapid shutdown system (RSS) that reduces array conductor voltage to 30V or less within 30 seconds of initiation. The rapid shutdown initiator must be at a readily accessible location and labeled per 690.56.

Compliant approaches:

• Module-level power electronics (MLPE): Microinverters or DC optimizers with integrated RSD
• Listed Rapid Shutdown System: RSI communicating with module-level devices via SunSpec or other protocol

Ground-mounted systems more than 5 feet from any building are exempt from 690.12.

See the full NEC 690.12 guide for equipment selection and labeling requirements.

690.13: Photovoltaic System Disconnect

A disconnecting means must be provided to disconnect the PV system from all wiring systems including the utility grid. Requirements:

• Must be externally operable without requiring access to energized parts
• Must be grouped with other disconnects when practical
• Must be marked to indicate the source it disconnects
• Must be accessible to utility personnel and first responders

For roof-mounted systems on residential buildings, the disconnect is typically at the main service panel or a dedicated exterior disconnect location.

Part IV: Wiring Methods — 690.31

NEC 690.31 specifies permitted wiring methods for PV systems:

Permitted Wiring Methods

Rooftop Conduit Requirements (690.31(G))

Conduit systems on rooftops must:

• Be installed as close to the roof surface as practical
• Account for temperature effects (add 22°C to ambient for derating per 310.15)
• Use appropriate fittings and supports per the conduit manufacturer’s instructions

690.31(E): Direct Burial

Conductors buried directly in the earth must be listed for direct burial (UF or USE-2). Standard THWN-2 is not rated for direct burial without conduit. PV wire must be installed in conduit for underground runs unless specifically listed for direct burial.

690.31(F): Flexible Cords and Cables

Module-to-module field wiring must use listed PV connectors (typically MC4 or equivalent). Field-installed connectors must be from the same manufacturer family to ensure proper locking engagement. Mixed-brand connectors are not permitted.

Part V: Grounding — 690.41 to 690.48

690.41: Ground Fault Protection

All PV systems must have ground fault protection. For most modern systems using transformerless (string) inverters:

• The inverter includes internal ground fault detection as part of its listing
• Transformerless inverters operate as ungrounded systems — neither conductor is intentionally connected to ground
• The inverter must be listed for ungrounded use and must include isolation monitoring

For systems with transformers or older designs using a grounded system:

• One conductor is intentionally grounded (the negative conductor in most cases)
• A ground fault protection device must detect and interrupt ground fault current

690.43: Equipment Grounding

All exposed metallic parts of the PV system (module frames, racking, conduit, enclosures) must be bonded together and connected to the equipment grounding conductor (EGC). The EGC must be sized per NEC Table 250.122 based on the overcurrent device protecting the circuit.

Module Frame Grounding: Module frames must be grounded unless the module is specifically listed as “ungrounded” (some bifacial modules with anodized frames). Grounding clips, grounding washers through the module mounting hole, or EGC attachment to dedicated module grounding points are all acceptable methods.

690.47: Grounding Electrode System

The PV system must connect to the premises grounding electrode system. For systems with DC voltages above 250V DC, a separate direct current grounding electrode system is required under NEC 2020.

Part VI: Marking and Identification — 690.51 to 690.56

All PV system components must be marked to identify their power source and operating characteristics.

Required Labels

All labels must use minimum 3/8-inch lettering and be reflective (visible in low light). Pre-printed listed labels meeting these requirements are commercially available from several manufacturers.

NEC 690 Compliance Checklist

Use this checklist before submitting a permit package:

Calculations:

• 690.7: Temperature-corrected Voc calculated using ASHRAE T_min; below voltage limit
• 690.8: Source and output circuit ampacity = 125% × Isc × all derating factors
• 690.9: OCPD rated for DC voltage and current; at least 125% of circuit current

Equipment:

• All equipment listed and appropriate for PV use
• Rapid shutdown system installed (building-mounted systems)
• Rapid shutdown initiator at accessible location
• DC-rated disconnects installed

Wiring:

• Wiring methods comply with 690.31
• Listed PV connectors from same manufacturer family
• Rooftop conduit derating applied

Grounding:

• Module frames bonded and grounded
• EGC sized per Table 250.122
• Grounding electrode connection made

Labeling:

• All required labels installed at correct locations
• Label size and reflectivity requirements met

Frequently Asked Questions

What is NEC Article 690?

NEC Article 690 is the solar photovoltaic systems section of NFPA 70 (National Electrical Code). It sets requirements for system voltage, conductor sizing, overcurrent protection, rapid shutdown, wiring methods, grounding, and labeling for all US solar PV installations.

Which NEC edition applies to solar installations in 2026?

Most jurisdictions are on NEC 2020 or NEC 2017 as of 2026. Colorado, Oregon, Washington, Virginia, and Massachusetts have adopted NEC 2023. Always confirm with the local AHJ.

What are the most important NEC 690 sections for solar permit packages?

690.7 (max voltage calculation), 690.8 (conductor sizing), and 690.12 (rapid shutdown) are the three sections that drive most AHJ plan review comments on residential permits. Get these three right and most permit submissions go through on first submission.