NEC Article 690: Solar PV Systems

Solar photovoltaic installation has moved from a niche specialty to a baseline competency for licensed electricians. Article 690 is the framework that governs every PV system on buildings, ground mounts, and parking canopies, and it has been one of the most heavily revised articles of the last three NEC cycles.

This guide walks through every section of Article 690 that commonly appears on journeyman and master licensing exams. Each rule is tied back to the exact NEC 2023 citation so you can flag the page in your code book before exam day.

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Article 690 Structure

Article 690 is organized into nine parts:

• Part I, General (690.1 through 690.6)
• Part II, Circuit Requirements (690.7 through 690.12)
• Part III, Disconnecting Means (690.13 through 690.17)
• Part IV, Wiring Methods and Materials (690.31 through 690.36)
• Part V, Grounding and Bonding (690.41 through 690.50)
• Part VI, Marking (690.51 through 690.56)
• Part VII, Connection to Other Sources (690.59)
• Part VIII, Energy Storage Systems (now relocated to Article 706)
• Part IX, Systems Over 1000 Volts (690.80 series)

Exam questions are concentrated in Parts II through V. Memorize those before exam day.

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Part II: Circuit Requirements

690.7, Maximum Voltage

PV source circuit voltage is the sum of the open circuit voltage (Voc) of the series connected modules, corrected for the lowest expected ambient temperature.

For one and two family dwellings, the maximum PV source and output circuit voltage cannot exceed 600 volts.

For other installations (commercial, utility, ground mount), the maximum voltage is limited only by the listing of the system components. Commercial PV strings commonly run at 1000 V DC, and utility scale designs at 1500 V DC.

Voltage correction example, three crystalline silicon modules in series:

• Module Voc at standard test conditions: 49.8 V
• Lowest expected ambient temperature: minus 10 degrees C
• Temperature correction factor from Table 690.7(A): 1.10
• Corrected per module Voc: 49.8 × 1.10 = 54.78 V
• 12 modules in series: 12 × 54.78 = 657.4 V

A 12 module string at this site would exceed the 600 V dwelling limit. The string would need to be shortened, or the installation would need to qualify as something other than a dwelling.

690.8, Circuit Current

This section determines the conductor size for every PV circuit.

Per 690.8(A)(1), the maximum current of a PV source circuit is calculated as 125 percent of the rated short circuit current (Isc) of the modules:

I_max = Isc × 1.25

Per 690.8(B), conductors carrying a continuous load (the PV current under all sunlight conditions counts as continuous) are sized at 125 percent of the calculated maximum current:

Conductor ampacity required = I_max × 1.25 = Isc × 1.5625

That 156.25 percent of Isc is the number to memorize for exam day. Every PV source and output conductor must have an ampacity of at least 156.25 percent of the module Isc, before any adjustment factors for temperature or conduit fill.

Worked example:

• Module Isc: 11.4 A
• Maximum current per 690.8(A)(1): 11.4 × 1.25 = 14.25 A
• Required conductor ampacity per 690.8(B): 14.25 × 1.25 = 17.81 A
• Selected conductor: 12 AWG copper THWN-2 at 75 degrees C, 25 A (from Table 310.16). Confirm this still holds after temperature and conduit fill adjustments are applied.

690.9, Overcurrent Protection

PV source and output circuits require overcurrent protection sized at not less than 125 percent of the maximum current from 690.8(A).

OCPD rating minimum = Isc × 1.25 × 1.25 = Isc × 1.5625

That is the same multiplier as the conductor sizing rule, which is intentional. The OCPD and the conductor scale together.

A common exam trap: fuses in PV combiners are sized to the next standard size up from the calculated minimum, per 240.4(B) round up rules.

690.12, Rapid Shutdown

Rapid shutdown is the change most cited by inspectors and most tested on exams in the post 2017 era.

Rapid shutdown is required for PV systems installed on or in buildings. The system must include a method to reduce the voltage of conductors outside the building or inside the array boundary to a safe level within 30 seconds of initiation.

Thresholds:

The array boundary is defined as 1 foot from the array in all directions. Module level power electronics, optimizers, and microinverters are the most common compliance methods because they can reduce module level voltage to a safe level when the inverter or rapid shutdown initiator is de energized.

Initiation: A rapid shutdown initiation device must be located at a readily accessible location outside the building or at a service equipment location. The initiator must be plainly labeled.

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Part III: Disconnecting Means

690.13, PV System Disconnecting Means

Every PV system must include a disconnecting means that isolates the system from all wiring systems in the building, including utility connected feeders, branch circuits, and storage systems.

Requirements:

• Readily accessible
• Externally operable without exposure to live parts
• Plainly indicates the open and closed position
• Capable of being locked in the open position, or located within sight of the equipment it controls
• Marked with the words PV SYSTEM DISCONNECT

The disconnect rating must be at least the maximum current from 690.8(A) (Isc × 1.25). It cannot be reduced below this value for any reason.

690.15, Disconnection of PV Equipment

Equipment level disconnects are required for each piece of PV equipment (inverter, charge controller, combiner) so that the equipment can be isolated from all sources of supply for service.

Equipment disconnects can be combined with the PV system disconnect if the disconnect interrupts all sources to the equipment.

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Part IV: Wiring Methods

690.31, Wiring Methods Permitted

Single conductor cable types PV wire and USE 2 are permitted in exposed outdoor PV source circuits within the array.

Inside buildings, PV DC circuits must be installed in metal raceways, metal enclosures, or Type MC cable when run in readily accessible areas, until they reach the first disconnect.

This is a fire department driven rule. First responders cutting into a building should not encounter unprotected DC PV conductors.

690.31(D), Marking of DC Circuits Inside Buildings

DC PV circuits inside buildings must be marked at intervals not greater than 10 feet, at every turn, and above and below penetrations of walls and ceilings, with the words:

WARNING: PHOTOVOLTAIC POWER SOURCE

Marking must be reflective and contrasting, in letters at least 3/8 inch tall, white on red.

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Part V: Grounding and Bonding

690.41, System Grounding

Modern PV systems are most commonly functional grounded systems.

A functional grounded system has one or more circuit conductors connected to ground through equipment such as the inverter that provides a reference but not a solid bond. This is the standard topology for current production string inverters and microinverters.

Solidly grounded PV systems and ungrounded PV systems are also recognized but uncommon in new construction.

690.43, Equipment Bonding

All exposed non current carrying metal parts of PV modules and equipment, including racking and mounting structures, must be bonded together and to the equipment grounding conductor.

Module clips and racking listed for grounding purposes (UL 2703 listed) bond the module frame to the racking without separate bonding jumpers.

690.45, Sizing of Equipment Grounding Conductors

Equipment grounding conductors for PV source and output circuits are sized per Table 250.122, based on the rating of the overcurrent protective device protecting the circuit.

Where no overcurrent device protects the circuit (parallel strings without combiner fuses), the EGC must be at least the size of the circuit conductors.

690.47, Grounding Electrode System

PV system grounding electrode conductors are sized per 250.66, with the same rules as service entrance GEC.

Where a building has an existing grounding electrode system, the PV system EGC is bonded to that system at the service equipment or at the first disconnect. A separate dedicated PV grounding electrode is not required when one is already present.

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Part VI: Marking

690.56, PV System Identification

PV systems must be marked at the service equipment with a permanent plaque or directory that includes:

• Location of the PV system disconnect
• Indication that the structure is supplied by both utility and PV source

For systems with rapid shutdown, the marking must also include the rapid shutdown initiator location and the words:

SOLAR PV SYSTEM EQUIPPED WITH RAPID SHUTDOWN

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Quick Reference: Key Numbers for Exam Day

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Related Reading

• NEC Article 250: Grounding and Bonding
• NEC Article 230: Services
• NEC Article 240: Overcurrent Protection
• NEC 2023 vs 2020 Changes
• Voltage Drop NEC Formula and Calculation
• Start Your Practice Test