NEC Article 690 is the part of the National Electrical Code written specifically for solar photovoltaic systems. If you install residential or commercial solar, almost every electrical decision on the job traces back to it: how many modules go in a string, why every roof has optimizers or microinverters, where the disconnects go, and what the red labels say. You do not need to quote it like an inspector. You do need to know what it controls, so you can spot problems before the inspector does.
This guide follows the 2023 NEC, the edition behind most current state adoptions and the one IAEI's PV column used for its change summaries. A 2026 edition now exists, and states adopt editions on their own schedules, so section numbers can differ in your area. The only edition that counts on a job is the one your authority having jurisdiction (AHJ) enforces.
What NEC Article 690 Covers
Article 690 applies to PV systems, whether interactive with the grid, stand-alone or both, with AC or DC output. Large-scale PV electric supply stations of 5,000 kW or more are covered separately by Article 691, as an IAEI NFPA Code Talk column explains. Three neighboring articles show up on solar jobs constantly:
- Article 705 covers interconnecting PV with other power sources, including the utility. That is where the busbar rules live.
- Article 706 covers energy storage systems over 1 kWh, so battery jobs bring it in.
- Article 110.3(B) says listed equipment must be installed per its instructions. On solar jobs, that makes the install manual part of the code.
The Sections You Touch Most
| Section | What it controls | What it means on the roof |
|---|---|---|
| 690.4 | General requirements; equipment must be listed or field labeled | Do not substitute unlisted parts |
| 690.7 | Maximum PV system DC voltage | String length limits, especially in cold climates |
| 690.8 | Circuit current and conductor sizing | Wire gauge and fuse ratings start here |
| 690.9 | Overcurrent protection | When fuses or breakers are needed on PV circuits |
| 690.11 | DC arc-fault protection | Built into most inverters; do not defeat it |
| 690.12 | Rapid shutdown on buildings | Why rooftop arrays use module-level electronics |
| 690.13 and 690.15 | PV system and equipment disconnects | Where switches go and what they isolate |
| 690.31 | Wiring methods | Securing conductors, raceways, PV wire |
| 690.41 to 690.47 | Grounding and bonding | Frames, racking and equipment grounding |
Voltage and Current: 690.7 and 690.8
Maximum voltage
Module open-circuit voltage rises as temperature falls. John Wiles's back-to-basics column for IAEI puts the change at about 0.5 percent per degree Celsius for crystalline silicon. So the coldest morning of the year, not a summer afternoon, sets your highest string voltage. Section 690.7 lets designers correct for that with a code table or, more precisely, the module's temperature coefficient.
The voltage ceilings matter: 600 V for one- and two-family dwellings and 1,000 V for other buildings, per IAEI's rapid shutdown review. Long strings on a house that look fine in July can exceed the limit in January. The 2023 edition also added 690.7(D), which requires the maximum DC voltage to be marked at one of several listed locations.
Circuit current
Section 690.8 starts with the module's short-circuit current at standard test conditions and multiplies it by 125 percent to get the maximum circuit current. IAEI notes that factor reflects sunlight stronger than an array should see for three hours or more. Conductors and overcurrent devices are then sized from that maximum current with further adjustments. Designers usually run those numbers, but you should know why the plan set calls for a given wire size, so you never downsize it in the field.
Arc-Fault and Ground-Fault Protection
Two built-in protections catch the faults that start PV fires. In its fire and personnel safety review, IAEI describes them this way under the 2020 NEC:
- Arc-fault (690.11): required on PV systems with DC circuits operating at 80 V or more. It targets series arcs from loose connections or damaged wires, and is usually built into the inverter, which shuts down and needs a manual restart. Exceptions include arrays not on buildings, circuits in metal raceways or enclosures, and detached structures used only for PV equipment.
- Ground-fault (690.41(B)): required for DC circuits over 30 V or 8 A. The device must detect the fault, then isolate the faulted circuit or stop delivering power, and indicate that a fault occurred.
For an installer, this explains a lot of callbacks. A connector that was not fully seated, or two different brands of connectors mated together, can trip arc-fault protection weeks later. The code also expects mated connectors to be listed together, as the IAEI inspection guide points out.
NEC 690.12 Rapid Shutdown, Explained
Rapid shutdown exists so firefighters can work on a roof without live DC conductors around them. According to IAEI's review of rapid shutdown and UL 3741, the rules evolved like this:
| Edition | Key requirement |
|---|---|
| 2014 | First rapid shutdown rules: conductors more than 10 feet from the array or 5 feet inside a building limited to 30 V within 10 seconds |
| 2017 | Array boundary defined as 1 foot from the array; outside it, 30 V within 30 seconds |
| 2017, effective Jan. 1, 2019 | Inside the boundary: 80 V within 30 seconds, which drove wide use of module-level power electronics |
| 2020 and 2023 | Same limits, plus the option of a listed PV hazard control system tested to UL 3741 |
The 80 V figure is why microinverters, optimizers and rapid shutdown devices are on nearly every residential roof: a single string of modules can easily exceed 80 V. The initiation device can be the service disconnect, the PV system disconnect, or a readily accessible switch clearly marked ON and OFF. The 2023 edition added exceptions for arrays not attached to buildings and for non-enclosed detached structures.
Disconnects, Wiring Methods and Bonding
Disconnects (690.13 and 690.15). The PV system disconnect separates the PV system from everything else in the building, and it has to be readily accessible. Equipment disconnects let someone safely isolate an inverter or other piece of equipment for service. The 2023 edition reorganized both sections without changing their basic purpose.
Wiring methods (690.31). Exposed PV conductors must be secured near module junction boxes with fastening that lasts as long as the modules. Loose wires rubbing on racking or roofing are a leading inspection failure, and a fire risk. DC circuits run inside buildings generally go in metal raceways or enclosures and must be marked.
Bonding (690.43). Exposed metal parts of module frames and racking must be bonded. A racking system listed to UL 2703 for the specific modules, installed per its manual, provides that bond. Our racking and roof types guide covers the hardware side.
Labels and the 120 Percent Rule
Labels are an easy inspection failure. Under the rapid shutdown rules, a permanent directory at the service equipment shows a roof diagram with the array location, and each rapid shutdown switch needs a label on it or within 3 feet that identifies it as the rapid shutdown switch for the solar system. Where a building has arrays both with and without rapid shutdown, the diagram must show which is which.
Interconnection is Article 705, not 690, but you will hear the 120 percent rule on every residential job. An IAEI calculations article based on the 2017 NEC explains it: the main breaker rating plus 125 percent of the inverter output current cannot exceed 120 percent of the busbar rating. On a 200 A panel with a 200 A main, that leaves room for 40 A of backfeed, and the solar breaker must sit at the opposite end of the bus from the main, with a warning label.
An Article 690 Field Checklist
- Know which NEC edition your AHJ enforces.
- Match string lengths exactly to the plan set; never add modules in the field.
- Fully seat every connector, and only mate connectors listed to work together.
- Secure exposed conductors off the roof surface and away from sharp edges.
- Install rapid shutdown devices on every module the design calls for.
- Confirm racking is listed for the modules and bonding hardware is installed per the manual.
- Place every required label before the inspection, including the roof diagram directory.
- Verify the backfed breaker size and position match the plan.
NABCEP exams lean heavily on this material, so studying the code pays off twice (see NABCEP Certification Explained).
Bottom Line
Learn Article 690 at the level of why things are done, not section-by-section recall. Know that cold raises voltage, that rapid shutdown is why module-level electronics are everywhere, that arc-fault trips usually trace back to connectors, and that labels and conductor management fail more inspections than anything exotic. If you want to grow into a lead, PV designer or NABCEP-certified role, code fluency is the skill that separates you, so pick up the edition your state enforces and read it alongside the jobs you are building.