Solar Photovoltaic (PV) Systems - National Electrical Code Requirements and Applications
This guide covers NEC Article 690 requirements for safe installation of solar PV systems, including grid-tied, stand-alone, and multimode systems.
This study guide is for educational purposes only. Always refer to the complete, most current edition of the National Electrical Code (NFPA 70) for official requirements. Local jurisdictions may have amendments to the NEC. Always obtain proper permits and inspections for all electrical installations.
Article 690 of the National Electrical Code provides requirements for the safe installation of electrical equipment, wiring, and components in solar photovoltaic (PV) systems. These requirements apply to all PV systems except those covered under Article 691 (Large-Scale PV Electric Supply Stations).
A solar PV system converts sunlight into electricity using photovoltaic cells. According to NEC, a PV system includes all components and subsystems that convert solar energy into electrical energy and necessary for system operation, including the interactive components with other energy sources.
Article 690 applies to PV systems that operate at or below 1000V, though some provisions apply to systems over 1000V. The article covers:
Requirement: Article 690 applies to solar PV electrical energy systems including the array circuit(s), inverter(s), and controller(s) for such systems. These systems may be interactive with other electrical power production sources or stand-alone with or without electrical energy storage.
Understanding key definitions is critical for proper application of Article 690:
| Term | Definition | Practical Significance |
|---|---|---|
| PV System DC Circuit | Any conductors between PV source circuits and the inverter input | Different requirements apply to DC vs AC side of system |
| Interactive System | A PV system that operates in parallel with and may deliver power to an electrical production and distribution network | Must comply with Article 705 requirements |
| Rapid Shutdown | Reduction of PV system voltage to 80V or less within 30 seconds of shutdown initiation | Critical firefighter safety requirement |
| PV Source Circuit | Conductors between modules and from modules to the common connection point of the DC system | Calculations for these circuits differ from other circuits |
Requirement: PV systems shall be permitted to supply a building or other structure in addition to any other electricity supply systems. All equipment must be listed and identified for PV system use.
When installing a PV system, ensure all components (inverters, combiners, disconnects) are specifically listed for solar PV applications. Using equipment not listed for PV use violates 690.4 even if the equipment is listed for general electrical use.
Requirement: The maximum PV system voltage is the highest voltage between any two conductors of the PV system. For modules rated 1000V or less, calculate using the lowest expected ambient temperature.
1. Determine module open-circuit voltage (Voc) from manufacturer specifications
2. Determine temperature correction factor for coldest expected temperature (NEC Table 690.7)
3. Multiply Voc by temperature correction factor
4. For series connections, multiply by number of modules in series
5. This gives maximum system voltage for component rating selection
690.7(C) Increased Voltage Limits: For dwelling units, the maximum voltage for PV systems is now permitted to be 1000V (increased from 600V) when the installation complies with all requirements for 1000V systems.
Requirement: The maximum current for PV circuits is calculated as 125% of the short-circuit current (Isc) marked on the module. For continuous current conditions, additional 125% factor applies.
If a PV module has Isc = 10A:
1. Maximum circuit current = 10A × 1.25 = 12.5A
2. For continuous operation (3+ hours) = 12.5A × 1.25 = 15.625A
3. Conductor ampacity must be at least 15.625A
4. Overcurrent device must be rated at least 15.625A (next standard size up)
When connecting modules in parallel, the conductors between modules and to the common connection point must be sized at least 125% of the module short-circuit current.
PV system conductors must have ampacity not less than 125% of the maximum currents calculated in 690.8(A). Adjustments for conditions of use (temperature, conduit fill) apply per NEC 310.15.
Requirement: PV system DC circuits must be protected against overcurrent. There are exceptions for certain conductor sizes and configurations. Overcurrent devices must be listed for DC operation and PV use.
| Circuit Type | Overcurrent Protection Required? | Common Exception |
|---|---|---|
| Single series string | Generally not required | 690.9(A) Exception: If conductors sized per 690.8(B) |
| Multiple parallel strings | Required for each string | Protection required at point of parallel connection |
| Battery circuits | Always required | Must be accessible and within battery enclosure |
| AC inverter output | Required per Article 705 | Standard AC circuit breaker typically used |
Requirement: Means shall be provided to disconnect all current-carrying conductors of a PV system from all other conductors in a building. The disconnecting means must be externally operable, indicate open/closed position, and be rated for the maximum circuit voltage and current.
PV system disconnects must be installed at readily accessible locations. For one- and two-family dwellings, the disconnect must be installed at a location normally accessible to first responders (not on the roof). This supports rapid shutdown requirements.
The PV system disconnecting means shall be one of the following:
The disconnecting means must have a rating not less than 115% of the maximum circuits current calculated per 690.8.
Requirement: PV systems on buildings shall have rapid shutdown to reduce shock hazard for emergency responders. Within 30 seconds of initiation, voltage must be reduced to 80V or less on the roof and to 30V or less within 1 ft of the array boundary.
690.12(B)(2) Expanded Rapid Shutdown: Rapid shutdown initiation now includes activation by a readily accessible switch at the service disconnecting means OR automatic shutdown upon loss of utility power for interactive systems.
1. Install rapid shutdown initiation switch at service disconnect location
2. Use listed rapid shutdown equipment (modules, inverters, combiners)
3. Ensure equipment reduces voltage to required levels within 30 seconds
4. Label all rapid shutdown equipment and initiation points clearly
5. Include rapid shutdown information in plans submitted for permit
Requirement: PV system wiring shall be installed in accordance with the applicable provisions of Article 300 and other relevant articles. Specific wiring methods are prescribed for different locations within the PV system.
Permitted wiring methods for PV circuits include:
| Location | Permitted Wiring Methods | Special Requirements |
|---|---|---|
| Module interconnection | Listed PV wire, USE-2, or other approved cables | Must be sunlight resistant if exposed |
| Within buildings | Raceways (conduit) with THWN-2, XHHW-2, or PV wire | DC conductors in metal raceway must have insulation rated for circuit voltage |
| Outdoor locations | PVC, RMC, IMC, EMT, or listed outdoor cables | Must be suitable for wet locations |
| Roof penetrations | Raceways with listed flashing or sealed penetrations | Must maintain weatherproof integrity of roof |
Single-conductor Type PV wire or USE-2 cables are permitted for module interconnections and within array. They must be installed in accordance with specific securing and protection requirements.
Multiconductor cables are permitted for interconnection of array components. When installed as exposed wiring, cables must be secured at intervals not exceeding 24 inches.
DC PV circuits inside buildings must be contained in metal raceway, metal enclosures, or consist of MC cable. Exceptions exist for PV circuits run inside the array boundary or for DC circuits from building-integrated PV modules.
Requirement: Connectors for PV systems must be polarized, require a tool to open, be listed for the application, and be of the latching or locking type. Mismatable connectors (different keying) must be used for different electrical systems.
Requirement: PV systems shall be grounded in accordance with Article 250. For PV systems, either functional grounding (for system operation) or equipment grounding (for safety) may be required.
PV systems with maximum system voltages over 50V must have one conductor grounded or have a functional ground. Functional grounding means a grounded system where the grounding is needed for proper system operation.
PV systems with maximum system voltages of 50V or less are not required to be grounded. However, equipment grounding is still required for safety.
The DC system grounding connection shall be made at any single point on the PV output circuit. This is typically done in the inverter or a dedicated DC grounding device.
Requirement: Exposed non-current-carrying metal parts of PV system equipment shall be grounded in accordance with Article 250, regardless of voltage.
All metal parts including module frames, racking, enclosures, and conduit must be bonded together and connected to the grounding electrode system. Equipment grounding conductors must be sized per NEC Table 250.122 based on overcurrent device rating.
Equipment grounding conductors for PV source and output circuits shall be sized per 250.122 but not smaller than 14 AWG. For PV arrays, additional requirements apply for grounding conductor sizing.
PV systems shall be connected to a grounding electrode system per 250.50. Where separate electrodes are used, they must be bonded together per 250.58.
□ Review manufacturer installation instructions for all components
□ Calculate maximum system voltage (690.7)
□ Calculate maximum circuit currents (690.8)
□ Size conductors and overcurrent protection (690.8, 690.9)
□ Determine grounding requirements (690.41-47)
□ Plan rapid shutdown implementation (690.12)
□ Install proper wiring methods (690.31)
□ Ground all equipment (690.43)
□ Install disconnects in accessible locations (690.13)
□ Install rapid shutdown equipment (690.12)
□ Use proper connectors (690.33)
□ Bond all metal parts (690.43)
□ Apply required labels (690.53-56)
□ Test system operation
□ Verify rapid shutdown function
□ Document system for inspector
□ Provide owner with operation manual
| Requirement | Primary NEC Article | Key Sections |
|---|---|---|
| General electrical requirements | Article 110 | 110.3(B), 110.14, 110.26 |
| Grounding and bonding | Article 250 | 250.4, 250.50, 250.122 |
| Overcurrent protection | Article 240 | 240.4, 240.6, 240.21 |
| Wiring methods | Article 300 | 300.3, 300.4, 300.5 |
| Connection to utility | Article 705 | 705.12, 705.20, 705.30 |
| Battery systems | Article 480 | 480.7, 480.9, 480.10 |
690.53 - DC PV Power Source: "WARNING: ELECTRIC SHOCK HAZARD - DO NOT TOUCH TERMINALS - TERMINALS ON BOTH THE LINE AND LOAD SIDES MAY BE ENERGIZED IN THE OPEN POSITION"
690.54 - Interactive System Point of Interconnection
690.55 - Photovoltaic Power Source (AC disconnect)
690.56 - Rapid Shutdown (type and location of initiation)
Labels must be durable, permanently affixed, and visible after installation.
This study guide summarizes key requirements of NEC Article 690 but is not a substitute for the complete code. Always consult the latest edition of NFPA 70 National Electrical Code for complete requirements. Local jurisdictions may have amendments. When in doubt, consult with a licensed electrical professional or local authority having jurisdiction (AHJ).