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Photovoltaic Systems

Written and maintained by SynC.

Rev4
IssuedOct 19, 2026
LicenseCC BY 4.0
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1 Scope

NOTE This standard governs the photovoltaic system as an electric power production source and the work that puts it into service: the modules, the inverters and the module-level electronics, the DC source and output circuits with their combiners, connectors, fuses, and disconnects, the rapid shutdown and arc-fault protection, the DC surge protection, the point and the method of interconnection with the premises wiring, the application to the serving utility and its permission to operate, the mounting system as a delegated design, the bonding of the array, the production meter and the monitoring, the commissioning tests, the performance acceptance, and the production guarantee, the warranties, and the spares. (1.1)
NOTE A photovoltaic system is governed by NFPA 70 Article 690 for everything from the module to the inverter output and by Article 705 for the connection of that output to a premises that already has a utility source; the building code and the fire code govern the array as a rooftop load, as a fire exposure, and as an obstacle to the fire department, and the serving utility governs the interconnection through its tariff and the IEEE 1547 settings it assigns. The equipment listings prove each product; the Article 690 calculations, the delegated racking design, and the interconnection agreement prove the system. (1.2)
NOTE The cell technology, the power conversion architecture, the rapid shutdown method, the mounting type, and the interconnection method are independent decisions and are carried as independent selections; every combination is built, and no selection here implies another. (1.3)
NOTE The array size in kilowatts DC and AC, the module count, the string lengths, the tilt, the azimuth, the row spacing, and the layout of the array are project-sized values that live on the photovoltaic drawings, and the capacity of the roof, the soil, and the foundations is established by the structural engineer of record and the geotechnical engineer; this standard requires that those documents exist and that the work follows them, and it does not restate them. (1.4)
NOTE The following are governed elsewhere and are outside this standard: (1.5)
  • the battery energy storage system, its power conversion system, its enclosure, and its hazard mitigation, under Battery Energy Storage SystemsBattery Energy Storage SystemsResolves to the current adopted revision.sync/battery-energy-storage-systems
  • the utility service, the service disconnecting means, and the metering of the service, under Electrical Service EntranceElectrical Service EntranceResolves to the current adopted revision.sync/electrical-service-entrance
  • the general-purpose enclosed switch and enclosed circuit breaker applied as a disconnecting means elsewhere on the premises, under Enclosed Switches And DisconnectsEnclosed Switches and DisconnectsResolves to the current adopted revision.sync/enclosed-switches-and-disconnects
  • building wire, feeders, and raceways beyond the array, under Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables, Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit, and Underground DuctbankUnderground Electrical Duct BanksResolves to the current adopted revision.sync/underground-ductbank
  • the grounding electrode system, the auxiliary electrode at an array, and the general rules for equipment grounding conductors, under Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding
  • the lightning protection system, under Lightning ProtectionLightning Protection SystemsResolves to the current adopted revision.sync/lightning-protection
  • the surge protective device at the AC point of interconnection as a product, under Surge Protective DevicesSurge Protective DevicesResolves to the current adopted revision.sync/surge-protective-devices
  • the switchboard or panelboard the system lands on, under Low Voltage SwitchboardsLow Voltage SwitchboardsResolves to the current adopted revision.sync/low-voltage-switchboards and PanelboardsPanelboardsResolves to the current adopted revision.sync/panelboards
  • the isolation transformer and the step-up transformer, under Low Voltage Dry Type TransformersLow-Voltage Dry-Type TransformersResolves to the current adopted revision.sync/low-voltage-dry-type-transformers and Medium Voltage TransformersMedium-Voltage Distribution TransformersResolves to the current adopted revision.sync/medium-voltage-transformers
  • the fault, coordination, and arc-flash studies, under Short Circuit StudyShort-Circuit StudyResolves to the current adopted revision.sync/short-circuit-study, Protective Coordination StudyProtective Device Coordination StudyResolves to the current adopted revision.sync/protective-coordination-study, and Arc Flash StudyArc-Flash StudyResolves to the current adopted revision.sync/arc-flash-study
  • the testing firm, its instruments, and its report, under Electrical Acceptance TestingElectrical Acceptance TestingResolves to the current adopted revision.sync/electrical-acceptance-testing
  • the flashing of roof penetrations and the roof covering itself, under Membrane RoofingMembrane RoofingResolves to the current adopted revision.sync/membrane-roofing, and the metal roof covering and the confirmation that it can carry the reactions of the attachments, under Metal Roof PanelsMetal Roof PanelsResolves to the current adopted revision.sync/metal-roof-panels
  • the piles and piers of a ground mount as constructed, under Deep FoundationsDeep Foundations (Piles and Drilled Piers)Resolves to the current adopted revision.sync/deep-foundations, and the steel structure of a carport or canopy, under Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing
  • the concrete pad under an inverter or a transformer, under Concrete PadsConcrete Equipment PadsResolves to the current adopted revision.sync/concrete-pads
  • the meters as products, under Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring, and the building automation system that reads the production data, under Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system
  • label material and lettering, under Equipment LabelingElectrical Equipment LabelsResolves to the current adopted revision.sync/equipment-labeling
  • the network cabling, under Structured CablingStructured Cabling SystemsResolves to the current adopted revision.sync/structured-cabling
  • electric vehicle supply equipment and its circuits, under Electric Vehicle ChargingElectric Vehicle Charging EquipmentResolves to the current adopted revision.sync/electric-vehicle-charging
  • the classification of loads and the transfer scheme where a multimode system serves a life-safety load, under Emergency And Standby PowerEmergency and Standby Power SystemsResolves to the current adopted revision.sync/emergency-and-standby-power
  • the anchors for fall protection during maintenance of the array, under Fall Protection AnchorageRoof and Facade Fall Protection AnchorageResolves to the current adopted revision.sync/fall-protection-anchorage
NOTE A utility-owned generating station under NFPA 70 Article 691, a stand-alone system with no utility interconnection, and solar thermal collectors are outside this standard and are not governed by another standard in this library. (1.6)
1.7 The photovoltaic system shall comply with NFPA 70 Articles 690 and 705 as adopted in Adopted Electrical CodeAdopted Electrical CodeParameterEach project supplies its own value.adopted-electrical-code, with the photovoltaic provisions of the adopted building code and fire code, and with the interconnection requirements of the serving utility.
1.8 The array layout, the module count, the string configuration, the tilt, the azimuth, the row spacing, and the locations of the inverters, combiners, and disconnects shall be as indicated on the photovoltaic plans and the photovoltaic one-line diagram.
1.9 Where a value stated on the photovoltaic drawings or the equipment schedules differs from the datasheet selection under this standard, the drawing shall govern for that system.

2 Referenced Standards

2.1 Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where the contract documents, the Authority Having Jurisdiction, the serving utility, or two referenced standards impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
NFPA 70 National Electrical Code (Articles 110, 250, 300, 310, 690, 705, and 706)
NFPA 70E Standard for Electrical Safety in the Workplace
NFPA 1 Fire Code (Section 11.12, Solar Photovoltaic Power Systems)
IFC International Fire Code (Section 1205, Solar Photovoltaic Power Systems)
IBC International Building Code (Chapter 15 rooftop photovoltaic provisions and Section 1607 photovoltaic panel system loads)
ASCE/SEI 7 Minimum Design Loads and Associated Criteria for Buildings and Other Structures (Chapters 13, 29, and 30)
UL 61730-1 Photovoltaic (PV) Module Safety Qualification, Part 1: Requirements for Construction
UL 61730-2 Photovoltaic (PV) Module Safety Qualification, Part 2: Requirements for Testing
IEC 61215-1 Terrestrial Photovoltaic (PV) Modules, Design Qualification and Type Approval, Part 1: Test Requirements
IEC 61215-2 Terrestrial Photovoltaic (PV) Modules, Design Qualification and Type Approval, Part 2: Test Procedures
IEC TS 62804-1 Photovoltaic (PV) Modules, Test Methods for the Detection of Potential-Induced Degradation, Part 1: Crystalline Silicon
UL 1741 Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources (including Supplements SA and SB)
IEEE 1547 Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power Systems Interfaces
IEEE 1547.1 Standard Conformance Test Procedures for Equipment Interconnecting Distributed Energy Resources with Electric Power Systems and Associated Interfaces
IEEE 519 Standard for Harmonic Control in Electric Power Systems
IEEE 2030.5 Standard for Smart Energy Profile Application Protocol
IEEE 1815 Standard for Electric Power Systems Communications: Distributed Network Protocol (DNP3)
SunSpec Modbus SunSpec Alliance Device Information Model Specification and Modbus Interface
UL 3141 Power Control Systems
UL 3741 Photovoltaic Hazard Control
UL 1699B Photovoltaic (PV) DC Arc-Fault Circuit Protection
UL 2703 Mounting Systems, Mounting Devices, Clamping/Retention Devices, and Ground Lugs for Use with Flat-Plate Photovoltaic Modules and Panels
UL 4703 Photovoltaic Wire
UL 854 Service-Entrance Cables
UL 6703 Connectors for Use in Photovoltaic Systems
UL 248-19 Low-Voltage Fuses, Part 19: Photovoltaic Fuses
UL 489B Molded-Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures for Use with Photovoltaic (PV) Systems
UL 1449 Surge Protective Devices
UL 50E Enclosures for Electrical Equipment, Environmental Considerations
NEMA 250 Enclosures for Electrical Equipment (1000 Volts Maximum)
IEC 62446-1 Photovoltaic (PV) Systems, Requirements for Testing, Documentation and Maintenance, Part 1: Grid Connected Systems, Documentation, Commissioning Tests and Inspection
IEC 61724-1 Photovoltaic System Performance, Part 1: Monitoring
IEC 61724-2 Photovoltaic System Performance, Part 2: Capacity Evaluation Method
IEC 61724-3 Photovoltaic System Performance, Part 3: Energy Evaluation Method
ANSI C12.1 Electric Meters, Code for Electricity Metering
ANSI/NETA ATS Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems
OSHA 29 CFR 1926 Subpart M Fall Protection
NOTE UL 1703 was the module listing standard for three decades and is withdrawn for new listings; a module offered today is listed to UL 61730, which is the UL adoption of IEC 61730 with the North American deviations, and a UL 1703 listing on a product data sheet marks either an old design or an old data sheet. IEC 61215 is the design qualification a module passes to prove it survives the thermal cycling, humidity-freeze, mechanical load, and hail of twenty-five years outdoors, and it is cited beside the safety listing because the listing alone does not test endurance. The SunSpec Modbus model is published by an industry alliance rather than a standards body and is cited because IEEE 1547 names it as one of the three interoperability interfaces available to an interactive resource. (2.3)

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for review before any photovoltaic equipment is released for manufacture or purchase:
  • product data for the modules, identifying the manufacturer, the model, the cell technology, the construction, the UL 61730 listing and the IEC 61215 qualification, the fire type, the electrical ratings at standard test conditions and at the nominal module operating temperature, the temperature coefficients of power, voltage, and current, the bifaciality factor where bifacial, the power tolerance, the maximum system voltage, the maximum series fuse rating, and the mechanical load ratings front and rear
  • product data for the inverters and the module-level electronics, identifying the UL 1741 listing and its supplement, the IEEE 1547 categories and functions supported, the DC input voltage window and maximum input current, the AC output voltage, current, and power, the weighted efficiency, the ground-fault, arc-fault, and rapid shutdown functions, the DC surge protection where integral, the enclosure type, and the operating temperature and altitude derating
  • the delegated design of the mounting system: drawings and calculations sealed by an engineer licensed in the state of the project, with the UL 2703 listing of the racking, the system fire class rating with the module furnished, the attachment or ballast layout, the loads delivered to the structure at each attachment or ballast block, and the wind, snow, and seismic loads the design is based on
  • the photovoltaic one-line diagram, showing every source circuit, combiner, output circuit, disconnect, overcurrent device, inverter, module-level electronic device, rapid shutdown device, surge protective device, meter, and the point of interconnection, with the conductor sizes and the voltage and current at each point
  • the array layout plan, showing the module count, the string assignment of every module, the tilt, the azimuth, the row spacing, the fire-service pathways and setbacks on a roof, and the locations of every piece of equipment
  • the maximum voltage calculation under NFPA 70 690.7, the current and ampacity calculations under 690.8, the overcurrent device selection under 690.9, and the voltage drop of the DC and AC circuits
  • the rapid shutdown system data, identifying the method, the devices, the initiator, the array boundary, and, where a hazard control system is furnished, the UL 3741 listing of the specific module, racking, wiring, and inverter combination
  • product data for the production meter, the monitoring system, and the sensors, with a points list of what is recorded and at what interval
  • the energy model, stating the annual production at the fifty percent probability of exceedance, the performance ratio, the losses assumed, the weather file used, and the DC-to-AC ratio
  • the utility interconnection application package as filed, and the interconnection agreement or the utility's conditional approval when received
Action Submittalscheckbox
☑ Module product data
☑ Inverter and module-level electronics product data
☑ Mounting system delegated design, sealed
☑ Photovoltaic one-line diagram
☑ Array layout plan
☑ Article 690 voltage, current, and overcurrent calculations
☑ Rapid shutdown system data
☑ Production meter, monitoring, and sensor data
☑ Energy model
☑ Interconnection application and agreement
3.1.2 No module, inverter, or racking component shall be released for purchase until the product data, the delegated mounting design, and the one-line diagram covering it have been reviewed and returned.
NOTE The module product data sheet is the document every other calculation reads from, and a substitution of module after the one-line diagram is reviewed changes the string voltage under 690.7, the circuit current under 690.8, the fuse rating under 690.9, the fire class rating under UL 2703, the attachment loads, and the energy model at once, which is why the module is released first and the rest follows it. (3.1.3)

3.2 Informational Submittals

3.2.1 The Contractor shall submit the following with or before the action submittals:
  • the qualifications of the module and inverter manufacturers, the installing contractor, the supervising installer, and the field testing firm, as Quality Assurance requires
  • the manufacturers' installation instructions for the modules, the inverters, the module-level electronics, the racking, and the connectors, including the torque values, the clamp zones, and the permitted module orientations
  • the written acceptance by the roofing manufacturer of the attachment or ballast system and its installation on the roof covering in place, where the array is on a roof, as the Installation article requires
  • the written confirmation from the structural engineer of record that the roof or the foundations carry the loads shown in the delegated mounting design, where that confirmation is not already in the contract documents
  • the utility correspondence on the interconnection application, including the IEEE 1547 categories, the export limit, the disconnect requirements, and the witness test requirements the utility has assigned
  • the commissioning plan, listing each test of IEC 62446-1 and of this standard, the instruments, the acceptance criteria, and the witnesses
  • the production guarantee instrument, where this standard requires one, with the model and the measurement method it is settled against
Informational Submittalscheckbox
☑ Manufacturer, installer, and testing firm qualifications
☑ Manufacturers' installation instructions
☑ Roofing manufacturer's acceptance of the attachment system
☑ Structural engineer of record confirmation of load capacity
☑ Utility interconnection correspondence
☑ Commissioning plan
☐ Production guarantee instrument

3.3 Closeout Submittals

3.3.1 The Contractor shall submit the following before the photovoltaic system is accepted:
  • the record drawings, showing the array as built with the string assignment of every module, the serial numbers of the inverters and the module-level electronics by location, the routing of every circuit, the locations of every disconnect and the rapid shutdown initiator, and the point of interconnection
  • the commissioning report in the form IEC 62446-1 requires, with the result of every test in the commissioning plan, the current-voltage curves and the thermographic images where those tests are selected, and the correction of every failure
  • the inverter settings as left, including the IEEE 1547 category, the trip and ride-through settings, the grid-support function settings, and the export limit, with the password or access level that protects them
  • the utility's permission to operate and the executed interconnection agreement
  • the performance acceptance test report, where a performance test is selected under this standard
  • the operation and maintenance data for the modules, the inverters, the module-level electronics, the racking, the monitoring system, and the production meter, with the manufacturers' maintenance schedules for the warranty terms
  • the warranty certificates for the modules, the inverters, the module-level electronics, the racking, and the monitoring service, registered in the Owner's name, and the installation and production guarantee instruments
  • the administrator credentials for the monitoring platform and the inverter interfaces, transferred to the Owner
  • the record of the Owner training this standard requires
  • a signed receipt from the Owner for the spare parts delivered
Closeout Submittalscheckbox
☑ Record drawings with string assignments and serial numbers
☑ IEC 62446-1 commissioning report
☑ Inverter settings as left
☑ Permission to operate and interconnection agreement
☐ Performance acceptance test report
☑ Operation and maintenance data
☑ Warranty, installation guarantee, and production guarantee documents
☑ Monitoring and inverter credentials transferred
☑ Owner training record
☑ Spare parts receipt
NOTE The string assignment on the record drawings is the document a technician reads when one string reads low ten years on; without it, finding the module behind the fault means lifting modules until the current returns, and an array whose record drawing was never made is maintained by that method for its whole life. (3.3.2)

4 Quality Assurance

4.1 Listings

4.1.1 Modules shall be listed and labeled to UL 61730-1 and UL 61730-2 by a Nationally Recognized Testing Laboratory, and shall carry the IEC 61215 design qualification for the module type furnished.
4.1.2 Inverters, module-level electronics, and interconnection system equipment shall be listed to UL 1741, and equipment that operates in parallel with the utility shall be listed to Supplement SB of UL 1741 as conforming to IEEE 1547 and tested to IEEE 1547.1, except where the serving utility requires Supplement SA in writing.
NOTE Supplement SA aligns the inverter with the California Rule 21 functions and Supplement SB demonstrates conformance to IEEE 1547-2018; the two are not interchangeable, nearly every utility outside California and most inside it now require SB, and an inverter listed to the supplement the utility did not ask for is rejected at interconnection review after it is installed. (4.1.3)
4.1.4 The mounting system, including its clamps, its bonding components, and its ground lugs, shall be listed to UL 2703 with the module furnished, and the system fire class rating under UL 2703 shall be established with that module.
4.1.5 A hazard control system furnished to satisfy rapid shutdown shall be listed to UL 3741 as the combination of module, module-level device where any, racking, wiring method, and inverter furnished, and a combination the listing does not cover shall not be accepted as a hazard control system.
4.1.6 Photovoltaic wire shall be listed to UL 4703, connectors to UL 6703, photovoltaic fuses to UL 248-19, circuit breakers in DC photovoltaic circuits to UL 489B, arc-fault protection to UL 1699B, DC surge protective devices to UL 1449 for photovoltaic DC application, and a power control system that limits export to UL 3141.
4.1.7 No listed product shall be modified in the field in a manner that departs from the configuration under which it was listed.

4.2 Manufacturer Qualifications

4.2.1 The module manufacturer and the inverter manufacturer shall each have produced the product type furnished for not less than the period indicated in the datasheet and shall each maintain a warranty service organization in North America.
Manufacturer Production Historyrange
Not less than
years
351020
NOTE Five years is the period most projects require and the period the common module and inverter makers all clear, which is why it is the default; a longer period narrows the field to the longest-established makers, and a shorter one or none admits a new cell technology or a new inverter platform that no maker has shipped for long, at the risk that the warranty outlives the company. A module warranty is only as good as the company honoring it in year twenty, so the period is a proxy for that company still existing. (4.2.2)
4.2.3 The module manufacturer shall state in the qualification statement the factory at which the modules furnished are produced and shall furnish the flash test data of each module shipped, identified by serial number.

4.3 Installer Qualifications

4.3.1 The photovoltaic system shall be installed by the installer indicated in the datasheet.
Installer Qualificationradio
○ Licensed electrical contractor with a NABCEP PV Installation Professional supervising the work on site
○ Licensed electrical contractor trained by the module, inverter, and racking manufacturers on the products furnished
○ Licensed electrical contractor holding the state's photovoltaic or solar contractor license where one exists
NOTE A NABCEP-certified supervisor is the qualification most Owners and incentive programs ask for and the one that proves photovoltaic competence independent of any product; manufacturer training proves competence on the products furnished and is the condition of most racking and inverter warranties; a state solar license is required in the states that issue one and proves nothing where none exists. Which is wanted depends on the state and on the program financing the system, so the field carries no default, and the three are often combined. (4.3.2)
4.3.3 The electrical connections, the disconnects, the overcurrent devices, and the interconnection shall be made by electricians licensed in the jurisdiction working under a licensed electrical contractor.
4.3.4 Each person who works inside the array boundary on energized DC circuits shall be qualified under NFPA 70E for the DC voltage present and shall be trained in the manufacturer's procedure for opening connectors under load.
4.3.5 The field tests this standard names shall be performed by a firm qualified under Electrical Acceptance TestingElectrical Acceptance TestingResolves to the current adopted revision.sync/electrical-acceptance-testing or by the installing contractor's own technicians, as the Testing article of this standard indicates.

4.4 Delegated Design of the Mounting System

4.4.1 The mounting system shall be designed by an engineer licensed in the state of the project, engaged by the Contractor or the racking manufacturer, for the loads of Adopted Building CodeAdopted Building CodeParameterEach project supplies its own value.adopted-building-code and ASCE/SEI 7 at the site, including the wind loads of ASCE/SEI 7 Chapter 29 for rooftop solar panels or Chapter 30 for a canopy, the snow load, the seismic loads of Chapter 13 for an attached or an unattached array for Seismic Design CategorySeismic Design CategoryParameterEach project supplies its own value.seismic-design-category, and the dead load of the array.
4.4.2 The delegated design shall state the reaction delivered to the roof structure or the foundation at every attachment or ballast block, and shall be checked by the structural engineer of record against the capacity of the roof or the foundations before the array layout is released.
NOTE The racking engineer designs the racking for the loads and reports what the racking puts into the building; whether the building carries it is the structural engineer of record's determination, and nothing in this standard transfers that determination to the Contractor or the racking manufacturer. An array laid out before that determination is made is the most common source of a redesign, because a ballasted array on a roof framed for a light membrane load moves the ballast to the columns and the array off the roof. (4.4.3)
4.4.4 The delegated design shall use the edition of ASCE/SEI 7 the adopted building code references, and the wind design shall use the exposure and the roof zone coefficients for the roof geometry of the project, with the array edge, corner, and interior zones set as that edition defines them.

4.5 Regulatory and Utility Requirements

4.5.1 The Contractor shall confirm in writing with the Authority Having Jurisdiction, before the action submittals, the edition of NFPA 70 in force and the rapid shutdown, arc-fault, and surge protection provisions it applies to the project.
NOTE Article 690 changed in each of the 2017, 2020, and 2023 editions in the rapid shutdown method inside the array, the arc-fault threshold, the maximum voltage, and the wiring methods on a roof, and jurisdictions adopt editions years apart; the edition the Authority Having Jurisdiction enforces, not the latest published, decides the equipment, which is why it is confirmed before the design is submitted. (4.5.2)
4.5.3 The Contractor shall confirm in writing with the serving utility, before the action submittals, the interconnection path and study the system falls under, the IEEE 1547 categories and the export limit the utility assigns, the utility's requirements for a visible, lockable disconnect and for metering, and whether the utility witnesses the commissioning.
4.5.4 The photovoltaic system shall not be operated in parallel with the utility until the interconnection agreement is executed and the utility's permission to operate is in hand.

5 Environmental and Service Conditions

5.1 Enclosure Type

5.1.1 The enclosure type of the inverters, the combiners, the disconnects, and the junction and pull boxes of the photovoltaic system shall be as indicated in the datasheet.
Enclosure Type per NEMA 250select
Type 1
Type 12
Type 3R
Type 4
Type 4X
NOTE Photovoltaic equipment stands with the array, on a roof or in a field, and the inverters, combiners, and disconnects of most systems are outdoors, which is why the field departs from the indoor Type 1 convention and defaults to Type 3R; string inverters are built in Type 4 or Type 4X enclosures as the manufacturer's standard and exceed the default without a change in product. Type 1 and Type 12 are the ratings of an inverter installed in an electrical room, with Type 12 for a dusty industrial room; Type 4 is gasketed against hose-directed water and wind-driven rain and is the rating of an exposed rooftop or coastal site; Type 4X adds corrosion resistance for salt air, de-icing chemical, or a chemical atmosphere. (5.1.2)
5.1.3 Enclosures shall comply with UL 50E and NEMA 250 for the type selected, and the type shall be marked on the enclosure.
5.1.4 Equipment installed outdoors, on a roof, or under a carport shall have an enclosure of Type 3R, Type 4, or Type 4X.
5.1.5 Equipment installed where the atmosphere carries salt, de-icing chemical, chemical vapor, or another corrosive agent, including a site within one mile of a saltwater coast, shall have a Type 4X enclosure.
5.1.6 Where the enclosure type these clauses require exceeds the datasheet selection at an installed location, the higher type shall be furnished at that location and the conflict reported to the Engineer of Record before procurement.
5.1.7 Raceway entries into a Type 3R, Type 4, or Type 4X enclosure shall be made only with fittings listed to maintain the enclosure type and only at the entry locations the manufacturer provides, and entries into the top of an outdoor enclosure shall be avoided where the manufacturer provides another location.

5.2 Temperature and Altitude

5.2.1 Inverters and module-level electronics installed outdoors, on a roof, or in an unconditioned space shall deliver their rated continuous output at Site Ambient Temperature MaximumSite Ambient Temperature MaximumParameterEach project supplies its own value.site-ambient-temperature-maximum, and where the manufacturer reduces the output above a stated ambient temperature, the output at the site maximum shall be stated in the product data and shall be the rating used in the energy model.
5.2.2 Inverters shall be derated for AltitudeAltitudeParameterEach project supplies its own value.altitude in accordance with the manufacturer's published correction factors where the altitude exceeds the rating basis of the listing, and the derated ratings shall be stated in the product data.
5.2.3 Modules, module-level electronics, connectors, and photovoltaic wire shall be rated for continuous operation from Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum to the cell and conductor temperatures reached in full sun at Site Ambient Temperature MaximumSite Ambient Temperature MaximumParameterEach project supplies its own value.site-ambient-temperature-maximum, and conductor ampacity on a roof shall include the temperature adder of NFPA 70 310.15 for the distance of the raceway above the roof where the adopted edition requires it.
NOTE A string inverter mounted on a roof in direct sun runs well above the air temperature, and a module in still air in full sun runs 25 °C to 35 °C above it, so the equipment is judged at the site maximum rather than at a nominal indoor value, and an inverter that derates at 45 °C delivers less than its nameplate through every summer afternoon the energy model counts on. (5.2.4)

5.3 Structural Loads at the Site

5.3.1 The mounting system shall be designed for the ultimate wind speed, the ground snow load, the exposure category, and the risk category stated on the structural general notes, and where the structural drawings state none, for the values of the adopted building code at the site.
5.3.2 A ballasted or an attached rooftop array shall be installed only where the structural drawings or the structural engineer of record's written confirmation show the roof framing designed for the array dead load, the ballast, the concentrated loads at the attachments, and the drifted snow the array causes.
5.3.3 Where Wind Borne Debris RegionWind Borne Debris RegionParameterEach project supplies its own value.wind-borne-debris-region places the site in a wind-borne debris region, modules shall carry the mechanical load ratings the delegated design requires for the design wind pressure at the array location, and the clamp zones used shall be those under which the module's load rating was established.

6 System Configuration

6.1 System Function

6.1.1 The function of the photovoltaic system shall be as indicated in the datasheet.
System Functionradio
● Utility-interactive, ceasing to energize on loss of the utility
○ Multimode, with storage under the energy storage standard, serving designated loads in an island
NOTE A utility-interactive system produces only while the utility is present and is the system of the large majority of commercial projects, which is why it is the default; a multimode system pairs the array with storage that forms an island when the utility fails, which puts the storage, the islanding device, and the island loads under Battery Energy Storage SystemsBattery Energy Storage SystemsResolves to the current adopted revision.sync/battery-energy-storage-systems and leaves the array, its inverter or its DC coupling, and its rapid shutdown here. (6.1.2)
6.1.3 Where the system is multimode, the coupling of the array to the storage, the anti-islanding coordination between the generation inverter and the storage inverter, and the island loads shall be as Battery Energy Storage SystemsBattery Energy Storage SystemsResolves to the current adopted revision.sync/battery-energy-storage-systems requires, and the array DC circuits, their overcurrent protection, and their rapid shutdown shall comply with this standard.

6.2 Maximum DC Voltage

6.2.1 The maximum photovoltaic system DC voltage shall be as indicated in the datasheet, and every module, conductor, connector, combiner, fuse, disconnect, surge protective device, and inverter input in the DC circuits shall be rated for not less than that voltage.
Maximum DC System Voltagerange
V
60010001500
NOTE A 1000 V system is the design of nearly every array on a commercial roof, because NFPA 70 690.7 limits DC circuits on or in a building other than a dwelling to 1000 V and the string, central, and optimizer products are built for it, which is why it is the default; 600 V is the limit on a dwelling and the design of older and of microinverter and AC-module arrays, where the DC never leaves the module; 1500 V is permitted only for an array not on or in a building and is the design of ground-mount and canopy arrays large enough to justify the longer strings, the smaller conductors, and the 1500 V equipment that goes with them. (6.2.2)
6.2.3 DC circuits on or in a building shall not exceed 1000 V, and a system rated 1500 V shall be installed only where the array is not located on or in a building, in accordance with NFPA 70 690.7.
6.2.4 The maximum voltage of each source circuit shall be calculated under NFPA 70 690.7 with Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum as the lowest expected ambient temperature, by the method indicated in the datasheet, and shall not exceed the maximum system voltage or the lowest voltage rating of any component in the circuit.
Maximum Voltage Calculation Methodradio
● Open-circuit voltage corrected by the module manufacturer's temperature coefficient
○ Open-circuit voltage corrected by the NFPA 70 Table 690.7(A) factor for crystalline modules
○ Industry-standard method under engineering supervision, for systems of 100 kW and larger
NOTE The manufacturer's coefficient is the method the module data sheet supports directly and the one nearly every design uses, which is why it is the default; the table factor is permitted for crystalline and multicrystalline modules where the coefficient is not available and is more conservative; the engineering-supervision method uses a statistical minimum temperature rather than the extreme and is permitted for systems of 100 kW and larger, where it adds a module or two to each string at the cost of a sealed calculation. (6.2.5)
NOTE A string one module too long is the defect the calculation exists to catch: the voltage is checked at standard test conditions and passes, the first cold clear morning after commissioning drives the open-circuit voltage past the inverter's input rating, and the inverter either refuses to start or is damaged, with the manufacturer's warranty excluding overvoltage. (6.2.6)

6.3 Power Conversion Architecture

6.3.1 The power conversion architecture of the system shall be as indicated in the datasheet.
Power Conversion Architectureselect
String inverters
String inverters with DC optimizers at the modules
Microinverters at the modules
Central inverter
NOTE String inverters convert the output of a group of strings at the roof or the ground, carry the lowest cost per watt at commercial scale, are replaced one at a time without a crane, and are the architecture of most commercial arrays, which is why the field defaults to them, with rapid shutdown inside the array met by module-level shutdown devices or a hazard control system; DC optimizers add a converter at each module that tracks that module's maximum power point, reports per-module data, and performs the module-level shutdown, which recovers the output of an array with partial shade, several orientations, or mismatched modules at the cost of a device per module and a dependence on the inverter maker that lists with it; microinverters convert at each module, carry no DC beyond the module, meet rapid shutdown inherently, and are replaced module by module, at the highest cost per watt and with the most devices on the roof, which suits a small or a heavily shaded array; a central inverter converts a whole array of several hundred kilowatts or more in one enclosure on a pad, at the lowest cost per watt at that scale and with a single point of failure that takes the whole array down, which suits a large ground mount or canopy. (6.3.2)
6.3.3 Where DC optimizers or microinverters are selected, the module-level device shall be listed with the inverter or the gateway it communicates with as one system, and a module-level device of one maker shall not be combined with the inverter of another unless the combination is listed.
6.3.4 Where a central inverter is selected, it shall be set on a pad constructed under Concrete PadsConcrete Equipment PadsResolves to the current adopted revision.sync/concrete-pads or in an electrical room with the working space NFPA 70 110.26 requires for its voltage, and the DC combiners and recombiners feeding it shall be furnished under this standard.

7 Modules

7.1 Cell Technology

7.1.1 The cell technology of the modules shall be as indicated in the datasheet, and every module in an array shall be of one manufacturer, one model, and one power class.
Module Cell Technologyselect
Monocrystalline silicon, tunnel oxide passivated contact (TOPCon)
Monocrystalline silicon, passivated emitter and rear cell (PERC)
Monocrystalline silicon, heterojunction (HJT)
Monocrystalline silicon, back contact
Thin film, cadmium telluride
NOTE Tunnel oxide passivated contact cells are the large majority of modules shipped since the industry moved off PERC, with efficiencies in the low to mid twenties, a lower temperature coefficient than PERC, and a bifacial construction as standard, which is why the field defaults to them; PERC modules are the previous generation, still produced, a point or two lower in efficiency and warmer in their coefficient, at the lowest price where stock remains; heterojunction cells carry the lowest temperature coefficient and the highest bifaciality of the silicon technologies and cost more, which pays on a hot site or a high-albedo ground mount; back-contact cells move the contacts to the rear and reach the highest efficiencies in a given frame, at a premium, which pays where the roof area is the constraint; cadmium telluride thin film carries a low temperature coefficient and a low embodied energy, is produced by few makers, is built in a frameless glass-glass form with its own racking, and is the choice of a large ground mount that buys on domestic content or on hot-climate yield rather than on efficiency per square foot. (7.1.2)
7.1.3 The module power tolerance shall be positive only, and the flash-test power of each module shipped shall be not less than its nameplate power.
7.1.4 Modules shall have passed the potential-induced degradation test of IEC TS 62804-1 at the maximum system voltage selected under this standard with a power loss not exceeding 5 percent, and the manufacturer shall state the result in the product data.
NOTE Modules of a given technology lose power when the array voltage drives ions through the encapsulant toward the cells, and the loss is largest at 1000 V and 1500 V on a hot humid site and on the modules at the negative end of a string; the test demonstrates that the module furnished resists it, and a module that was never tested cannot be shown to. (7.1.5)

7.2 Module Construction

7.2.1 The construction of the modules shall be as indicated in the datasheet.
Module Constructionradio
○ Glass front, polymer backsheet, monofacial
○ Glass front, glass rear, bifacial
○ Glass front, glass rear, monofacial
NOTE A polymer backsheet is the lighter and lower-cost construction and is what a roof whose load capacity is the constraint is specified with, and it is the construction whose backsheets have cracked in the field on some product lines after a decade; a glass-glass bifacial module collects the light reflected from the roof or the ground onto its rear face, which adds from a few percent on a dark membrane to twenty percent or more on a white roof or a high-albedo ground mount, carries a longer performance warranty on most product lines, and weighs more; a glass-glass monofacial module has the rear glass without the bifacial cell and is bought for the durability alone. The construction follows the roof capacity and the albedo, so the field carries no default. (7.2.2)
7.2.3 Where bifacial modules are selected, the short-circuit current used in the NFPA 70 690.8 calculations shall include the rear-side gain the manufacturer publishes for the mounting height, the row spacing, and the albedo of the installation, and the inverter maximum input current shall be checked against the same value.
7.2.4 The frame of the modules shall be as indicated in the datasheet.
Module Frameradio
● Anodized aluminum frame
○ Frameless
NOTE A framed module is clamped or bolted by its frame, bonds through the frame to the UL 2703 racking, and is the construction of nearly every module on the market, which is why the field defaults to it; a frameless module is held by edge clamps bearing on the glass, is bonded only where a rail or clamp is listed to bond it, and is the construction of the cadmium telluride product and of a few glass-glass silicon lines, and it is installed only with the racking listed for it. (7.2.5)

7.3 Module Power Rating

7.3.1 The nameplate power of the modules at standard test conditions shall be as indicated in the datasheet.
Module Nameplate Power at Standard Test Conditionsrange
Not less than
W
300800
Per drawings — the photovoltaic equipment schedule (deferred by default)
NOTE The module power is the product of the technology, the cell count, and the format the manufacturer builds, and with the module count on the drawings it sets the array size, so the value is read from the photovoltaic equipment schedule; a module of higher power in the same frame dimensions is accepted against the schedule value, and one in a larger frame changes the layout and the attachment loads and is a substitution. (7.3.2)
7.3.3 Each module shall bear the nameplate NFPA 70 690.51 requires, stating the open-circuit voltage, the short-circuit current, the maximum power voltage and current, the maximum power, the maximum system voltage, and the maximum series fuse rating.

7.4 Fire Classification

7.4.1 The system fire class rating of the modules with the mounting system under UL 2703 shall be as indicated in the datasheet.
System Fire Class Ratingselect
Class A
Class B
Class C
Derived — the roof covering fire classification that Adopted Building CodeAdopted Building CodeParameterEach project supplies its own value.adopted-building-code requires for the roof the array is installed on (by default)
NOTE The building code requires a rooftop array to carry the fire classification it requires of the roof covering beneath it, and the classification is established for the module and the racking together under UL 2703, because the gap between the module and the roof changes how a fire spreads under the array; a module's own fire type under UL 61730 is one input to that system rating and is not the rating itself. The roof classification is set by the construction type and the occupancy, which is why the field is derived from it. (7.4.2)
7.4.3 A rooftop array shall carry a system fire class rating not lower than the roof covering classification the adopted building code requires for the building, established by the UL 2703 listing of the racking with the module furnished and the module's fire type under UL 61730.

8 Inverters

8.1 Interconnection Functions

8.1.1 The IEEE 1547 normal performance category of the inverters shall be as indicated in the datasheet.
IEEE 1547 Normal Performance Categoryradio
○ Category A
○ Category B
Per drawings — the utility interconnection agreement (deferred by default)
8.1.2 The IEEE 1547 abnormal performance category of the inverters shall be as indicated in the datasheet.
IEEE 1547 Abnormal Performance Categoryradio
○ Category I
○ Category II
○ Category III
Per drawings — the utility interconnection agreement (deferred by default)
NOTE The serving utility assigns both categories in the interconnection agreement and the inverters are set to them, which is why both fields are deferred to that document. Normal Category A requires the minimum reactive power capability; Category B requires more and the volt-var and volt-watt functions, and most utilities now assign it to photovoltaic inverters. Abnormal Category I rides through the least disturbance, Category II rides through the disturbances a bulk-system event imposes, and Category III rides through the most and is assigned on circuits with a high penetration of distributed resources, where the utility wants every inverter to stay connected through a fault elsewhere. (8.1.3)
8.1.4 The inverters shall provide the constant power factor, voltage-reactive power, active power-reactive power, voltage-active power, and frequency-droop functions of IEEE 1547, each settable in the field, and shall be set to the values of the interconnection agreement, recorded in the settings as left, and protected from change by a password or a utility-controlled access level.
8.1.5 The anti-islanding protection shall detect the loss of the utility and cease to energize the utility side within the time IEEE 1547 requires, by a method stated in the product data, and the inverters shall not reconnect until the utility has returned within the IEEE 1547 enter-service criteria for the time the serving utility requires.
8.1.6 The export of power from the photovoltaic system to the utility shall be as indicated in the datasheet.
Export to the Utilityradio
○ Export permitted up to the limit in the interconnection agreement
○ Limited export enforced by a power control system listed to UL 3141
○ No export, enforced by a power control system listed to UL 3141 or a reverse-power relay
Per drawings — the utility interconnection agreement (deferred by default)
NOTE Whether the array is allowed to push power past the service point is the utility's decision in the interconnection agreement, which is why the field is deferred to it. A system permitted to export sells its surplus under net metering or a tariff and needs the full interconnection review; a limited-export system is held below the circuit's hosting capacity and often clears a shorter review; a non-export system is interconnected under the simplest review and is the arrangement where the utility will not accept generation on the circuit or where the array is sized to the daytime load. The power control system that enforces a limit is listed to UL 3141 and recognized by NFPA 70 705.13, and it is also one of the devices 705.12 recognizes for satisfying the bus limits at a load-side interconnection. (8.1.7)
8.1.8 Where limited or no export is selected, the power control system shall measure the power at the service point or at the point the interconnection agreement names, shall hold the export at or below the limit within the time its listing states, and shall reduce the inverter output to zero on loss of the measurement.

8.2 AC Output

8.2.1 The AC output voltage and phase of the inverters at the point of interconnection shall be as indicated in the datasheet.
Inverter AC Output Voltage and Phaseselect
240/120 V, 1Φ
208Y/120 V, 3Φ
480Y/277 V, 3Φ
600Y/347 V, 3Φ
Medium voltage, through a step-up transformer
Per drawings — the photovoltaic one-line diagram (deferred by default)
NOTE The inverter output matches the bus it lands on, which the one-line diagram fixes, and where the array is large relative to a 208 V service the inverters are furnished at 480 V and a step-down transformer is placed between them and the bus, or the array is interconnected at medium voltage through its own transformer; the transformer in either case is furnished under its own standard and the loss it adds is carried in the energy model. (8.2.2)
8.2.3 The inverters shall deliver their rated output at the power factor the interconnection agreement requires at the point of interconnection, and the harmonic current they inject shall comply with IEEE 1547 and with IEEE 519 at the point of common coupling.
8.2.4 The weighted efficiency of the inverters shall be not less than the value indicated in the datasheet.
Inverter Weighted Efficiencyrange
Not less than
%
9499.5
NOTE The weighted efficiency is the California Energy Commission figure the inverter listing publishes, averaged over the loading profile an array actually runs at, and it is the figure the energy model uses; transformerless string inverters publish in the upper nineties, central inverters at the top of that range, and microinverters a point or two lower. The value follows the architecture selected, so the field carries no default. (8.2.5)
8.2.6 The ratio of the array nameplate DC power to the inverter rated AC power shall not exceed the value indicated in the datasheet.
DC-to-AC Ratiorange
Not more than
ratio
11.6
NOTE An array larger than its inverter clips its output at midday on clear days and gains more energy in the mornings, the afternoons, and the cloudy months than it loses at noon, up to a ratio the energy model finds and the inverter's maximum input current permits; ratios between 1.2 and 1.35 are where most commercial designs land, a ratio near 1.0 suits a utility that limits AC capacity tightly against DC, and a higher ratio suits an array paired with storage that recovers the clipped energy. The value is an energy-model result, so the field carries no default. (8.2.7)
8.2.8 The inverter maximum DC input current, the maximum input voltage, and the maximum power point tracking window shall be matched to the source circuits connected to it, with the voltage at Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum below the maximum input and the voltage at the maximum cell temperature above the tracking minimum.

8.3 Ground-Fault and Arc-Fault Protection

8.3.1 The photovoltaic system shall be provided with DC ground-fault protection in accordance with NFPA 70 690.41, integral to the inverter or by a separate listed device, and the protection shall detect the fault, interrupt the faulted circuit or the inverter output, and indicate the fault at the inverter and through the monitoring system.
8.3.2 Where a non-isolated inverter is furnished, the manufacturer shall state in the product data how the inverter detects a ground fault and an insulation deterioration on the array and how it limits DC injection into the AC system.
8.3.3 DC circuits operating at 80 V or more between any two conductors shall be protected by a listed photovoltaic arc-fault circuit interrupter or by inverter-integral arc-fault protection listed to UL 1699B, in accordance with NFPA 70 690.11, and the protection shall be verified compatible with the module-level electronics and the rapid shutdown devices furnished.
NOTE Arc-fault detection reads a signature in the DC current, and a module-level device, a long home run, or a combiner of another maker can mask that signature or mimic it; the compatibility of the detector with everything on the DC side is a listing question the inverter maker answers in writing, and a system assembled from parts whose makers never tested them together trips on nuisance arcs or misses the real one. (8.3.4)

9 Rapid Shutdown

9.1 Rapid Shutdown Method

9.1.1 The photovoltaic system installed on or in a building shall include a rapid shutdown function in accordance with NFPA 70 690.12 for the adopted edition, and the method of controlling the conductors inside the array boundary shall be as indicated in the datasheet.
Rapid Shutdown Method Inside the Array Boundaryradio
○ Module-level shutdown devices or module-level power electronics
○ Photovoltaic hazard control system listed to UL 3741
○ Rapid shutdown not required, array not on or in a building
NOTE Module-level devices open or short each module or each pair of modules when the initiator operates, bring every conductor in the array to the limit within the time, work with any racking and any wiring method, and add a device per module or per two modules that communicates with or is powered by the inverter; a hazard control system listed to UL 3741 reaches the same level of protection for a firefighter by the construction of the array itself, with the specific modules, racking, wiring, and inverter tested as a combination, and it removes the module-level devices at the cost of being bound to that listed combination for the life of the system and to the few combinations listed; an array that is not on or in a building, as a ground mount or a detached canopy, is outside 690.12 and needs neither. The method follows the architecture and the mounting selected, so the field carries no default. (9.1.2)
9.1.3 Conductors leaving the array boundary shall be reduced to not more than 30 V within 30 seconds of rapid shutdown initiation, and conductors inside the array boundary shall be reduced to not more than 80 V within 30 seconds where module-level devices or electronics are furnished, in accordance with NFPA 70 690.12.
9.1.4 Where a hazard control system is furnished, the modules, the module-level devices where any, the racking, the wiring method, and the inverter shall be the combination the UL 3741 listing names, and no component of the combination shall be substituted without a listing that covers the substitute.
9.1.5 The array boundary shall be as NFPA 70 690.12 defines it for the adopted edition, shall be shown on the array layout plan, and the rapid shutdown label shall be placed and worded as the Identification article requires.

9.2 Rapid Shutdown Initiation

9.2.1 The rapid shutdown initiation device shall be as indicated in the datasheet.
Rapid Shutdown Initiation Deviceradio
○ The service disconnecting means
○ The photovoltaic system disconnecting means
○ A dedicated rapid shutdown switch at a readily accessible outdoor location
NOTE Initiating from the service disconnect lets the fire department shut down the array with the same switch that kills the building and is the arrangement most fire departments ask for on a building with one service; initiating from the photovoltaic system disconnect works where that disconnect is outdoors and readily accessible, and fails where it is in an electrical room; a dedicated switch at the exterior near the fire department connection gives responders one marked device whatever the service arrangement and is required by some jurisdictions. The device follows the service arrangement and the fire department's preference, so the field carries no default. (9.2.2)
9.2.3 The initiation device shall be readily accessible, shall be located outside the building or at the service equipment, shall not be inside a locked room or behind a locked gate the fire department cannot open, and shall initiate rapid shutdown of every photovoltaic system on the building when operated.
9.2.4 Where more than one initiation device serves a building, operation of any one shall initiate rapid shutdown of every system, and the devices shall be marked as the Identification article requires.
9.2.5 The rapid shutdown function shall operate on loss of AC power to the inverter whether or not the initiation device is operated, so that an inverter that loses the utility brings the array conductors to the limit without a person at the switch.

10 DC Circuits, Combiners, and Disconnects

10.1 Source and Output Circuit Conductors

10.1.1 Single-conductor cable exposed outdoors within the array shall be of the type indicated in the datasheet, and the home runs and the output circuits beyond the array shall be building wire and raceway under Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables and Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit.
Exposed Single-Conductor Cable Within the Arrayradio
● Photovoltaic wire listed to UL 4703
○ USE-2 listed to UL 854
NOTE Photovoltaic wire is the cable the modules themselves are fitted with, is rated 1000 V or 1500 V, sunlight-resistant, wet-rated, flexible, and permitted by NFPA 70 690.31 for every exposed single-conductor application within the array including an ungrounded array, which is why the field defaults to it; USE-2 is permitted for the same exposed runs on a functionally grounded array and costs less in the larger sizes, and it is rated 600 V, which limits it to a 600 V system. (10.1.2)
10.1.3 Source circuit conductors shall be sized to the currents of NFPA 70 690.8 with the short-circuit current multiplied by 125 percent for the maximum circuit current, or determined under engineering supervision for a system of 100 kW and larger as 690.8 permits, and with the conductor ampacity corrected for the rooftop temperature, the conduit fill, and the continuous duty of 690.8(B).
10.1.4 DC circuits inside a building shall be installed in a metal raceway, in Type MC cable listed for the purpose, or in a metal enclosure from the point of penetration to the first readily accessible disconnecting means, in accordance with the provisions of NFPA 70 690.31 for DC circuits on or in a building, and shall be marked as the Identification article requires.
10.1.5 Exposed cable within the array shall be supported and secured at intervals not exceeding those the cable listing and NFPA 70 690.31 permit, shall be kept off the roof surface and out of standing water, shall be protected from the module edges and the racking by clips or sleeves listed for the purpose, and shall not be secured with ties that degrade in sunlight.
NOTE Cable lying on a roof membrane is the most common finding of a five-year inspection: the ties have failed, the cable has abraded on the module frames, and the insulation at the low points has been under water every winter, and an insulation fault that the ground-fault detector then finds is traced to a cable tie that cost a cent. (10.1.6)

10.2 Connectors

10.2.1 Connectors in the DC circuits shall be listed to UL 6703, rated for the maximum system voltage and the circuit current, of a locking type requiring a tool to open where readily accessible, and the mating halves of each connection shall be of the same manufacturer and series unless the combination is listed as intermateable, in accordance with NFPA 70 690.33.
NOTE Connectors of different makers engage mechanically and fail electrically; a mismatched pair that heats, arcs, and melts is the leading cause of fire in a photovoltaic array, and the connector on the module lead sets the series for every field-installed connector, which is why the module connector series is stated in the product data and the field connectors and the crimp tool are bought to it. (10.2.2)
10.2.3 Field-installed connectors shall be assembled with the crimp tool and the die the connector manufacturer specifies for the conductor furnished, and the installer shall verify each crimp by the pull or inspection method the manufacturer's instructions state.

10.3 Combiners and Overcurrent Protection

10.3.1 The source circuits shall be combined by the provision indicated in the datasheet.
Source Circuit Combining Provisionradio
○ Fused combiner boxes located at the array
○ Fuse holders integral to the inverter DC input
○ Wiring harnesses with in-line fuses at the array
NOTE A combiner box at the array collects the strings of a block, carries a fuse for each, a disconnect where the design calls for one, and the DC surge protective device, and reduces the home runs to one output circuit, which suits a central inverter or a string inverter far from its strings; fuse holders in the inverter input are the arrangement of most string-inverter arrays, where each string runs to the inverter and the inverter holds the fuses, so that no combiner stands on the roof; in-line fused harnesses are factory-made assemblies that combine strings at the racking and suit a large ground mount with trackers, where they save the labor of a combiner at each row. The provision follows the architecture and the distance from the strings to the inverter, so the field carries no default. (10.3.2)
10.3.3 Overcurrent devices in DC photovoltaic circuits shall be furnished where NFPA 70 690.9 requires them, shall be photovoltaic fuses listed to UL 248-19 or circuit breakers listed to UL 489B, rated for the maximum system voltage and for not less than 125 percent of the maximum circuit current, and shall not exceed the maximum series fuse rating of the module.
10.3.4 Where the sum of the short-circuit currents of the parallel source circuits that can backfeed a circuit does not exceed the ampacity of its conductors and the maximum series fuse rating of its modules, overcurrent protection of that circuit is not required by 690.9, and the calculation that shows it shall be included in the action submittals.
10.3.5 Combiner boxes shall be listed, shall carry the enclosure type the Environmental and Service Conditions article requires for their location, shall have touch-safe fuse holders rated for the fuse furnished, and shall be furnished with a DC disconnecting means where the one-line diagram shows one at the combiner.

10.4 DC Disconnecting Means

10.4.1 The photovoltaic system DC disconnecting means and the isolating devices at the inverter input shall be furnished as NFPA 70 690.13 and 690.15 require, in the form indicated in the datasheet.
Inverter DC Disconnecting Meansradio
● Integral to the inverter, load-break rated, lockable
○ Separate enclosed DC-rated disconnect switch at the inverter
NOTE Nearly every string inverter and central inverter is furnished with an integral load-break DC disconnect that opens every ungrounded conductor and locks open, which is why the field defaults to it; a separate enclosed DC switch is added where the Authority Having Jurisdiction or the Owner requires a disconnect that is not part of the inverter, where the inverter is mounted out of reach, or where the inverter furnished has only an isolating device, and it is a DC-rated switch rated for the maximum system voltage, the circuit current, and the DC interrupting duty of a photovoltaic source. (10.4.2)
10.4.3 A DC disconnecting means shall open every ungrounded conductor of the circuit simultaneously, shall be rated for the maximum system voltage and the maximum circuit current, shall be load-break rated where NFPA 70 690.15 requires a load-break device, shall be lockable in the open position, and shall be marked with the voltage and the current as the Identification article requires.
10.4.4 An isolating device that is not load-break rated shall be marked as such and shall be opened only after the inverter has ceased to operate, and a connector used as an isolating device shall be of the tool-opened locking type NFPA 70 690.33 requires.
NOTE A DC arc does not extinguish at a current zero as an AC arc does, so a switch rated for AC and opened under DC load draws an arc that does not stop, which is why every DC disconnect carries a DC rating for the voltage and current it opens and why an isolating device that has none is opened only on a dead circuit. (10.4.5)

10.5 DC Surge Protection

10.5.1 Surge protection of the DC circuits shall be as indicated in the datasheet.
DC Surge Protectionradio
○ Surge protective device integral to the inverter DC input
○ Separate DC surge protective device at each inverter input and at each combiner
○ No DC surge protection beyond the inverter listing
NOTE An array is a wide conductor loop on the highest part of a building, and a nearby strike induces a surge in it that reaches the inverter input; an integral device protects the inverter at no added cost and is furnished in most string inverters; a separate device at each combiner adds protection at the array end of long home runs on a ground mount or a large roof, and is the arrangement where the building has a lightning protection system or the site has a high flash density; no protection beyond the listing leaves the inverter's own input stage as the protection and is the arrangement of a small array on a low building in a low-flash region. The arrangement follows the array extent and the exposure, so the field carries no default. (10.5.2)
10.5.3 A DC surge protective device shall be listed to UL 1449 for photovoltaic DC application, rated for the maximum system voltage, connected positive to negative and each pole to the equipment grounding conductor, and furnished with a status indicator readable without opening the enclosure.
10.5.4 Where the building has a lightning protection system, the bonding of the array and the surge protection of the DC and AC circuits shall be coordinated with Lightning ProtectionLightning Protection SystemsResolves to the current adopted revision.sync/lightning-protection, and the surge protective device at the AC point of interconnection shall comply with Surge Protective DevicesSurge Protective DevicesResolves to the current adopted revision.sync/surge-protective-devices.

11 Interconnection

11.1 Interconnection Method

11.1.1 The method by which the photovoltaic system connects to the premises wiring shall be as indicated in the datasheet.
Interconnection Methodradio
○ Load side of the service disconnecting means, under NFPA 70 705.12
○ Supply side of the service disconnecting means, under NFPA 70 705.11
○ Dedicated service for the photovoltaic system
Per drawings — the one-line diagram (deferred by default)
NOTE A load-side connection backfeeds a breaker in an existing switchboard or panelboard and is limited by the bus rules of NFPA 70 705.12, of which the 120 percent rule is the best known: the inverter breaker and the main together are limited to 120 percent of the bus rating, with the inverter breaker at the opposite end of the bus from the main, and the alternatives of 705.12 let a power control system or a sum-of-breakers calculation serve where the bus will not; a supply-side connection taps the service conductors ahead of the service disconnect under 705.11, avoids the bus limits entirely, and requires a service-rated disconnect, service-entrance conductors, and the utility's agreement, which Electrical Service EntranceElectrical Service EntranceResolves to the current adopted revision.sync/electrical-service-entrance governs on its side of the tap; a dedicated service gives the array its own meter and service and is the arrangement of a tariff that meters generation separately. The method is a one-line decision and is deferred to that drawing. (11.1.2)
11.1.3 A load-side connection shall comply with NFPA 70 705.12, with the backfed breaker rated for the inverter output under 705.30, located as 705.12 requires, and the bus and the conductors it lands on checked against the applicable rule of 705.12(B), and the check shall be included in the action submittals.
11.1.4 A supply-side connection shall be made with the tap conductors, the overcurrent device, and the disconnecting means NFPA 70 705.11 requires, and the disconnecting means, the service conductors, and the tap shall comply with Electrical Service EntranceElectrical Service EntranceResolves to the current adopted revision.sync/electrical-service-entrance.
11.1.5 The equipment at the point of interconnection and its bus ratings are governed by the standard for that equipment named in Scope, and the fault current contribution of the inverters, as the manufacturer publishes it with its duration, shall be stated in the product data for the study under Short Circuit StudyShort-Circuit StudyResolves to the current adopted revision.sync/short-circuit-study.

11.2 AC Disconnecting Means

11.2.1 The photovoltaic system AC disconnecting means shall be furnished as NFPA 70 690.13 and 705.20 require, and a utility-accessible disconnect shall be furnished as indicated in the datasheet.
Utility-Accessible AC Disconnectradio
○ Visible-break, lockable disconnect at the location the utility requires, accessible to the utility at all hours
○ Not required by the serving utility
Per drawings — the utility interconnection requirements (deferred by default)
NOTE Most utilities require a lockable, visible-break AC disconnect outdoors near the meter that their crews can open before working on the circuit, some accept the inverter's own disconnect or the listed anti-islanding function, and the requirement is stated in the utility's interconnection handbook, which is why the field is deferred to it. (11.2.2)
11.2.3 The AC disconnecting means shall open every ungrounded conductor of the inverter output, shall be rated for the inverter maximum output current and the available fault current at its terminals, shall be lockable in the open position, shall be of the form the Device Family article of Enclosed Switches And DisconnectsEnclosed Switches and DisconnectsResolves to the current adopted revision.sync/enclosed-switches-and-disconnects describes for a UL 98 switch or a UL 489 breaker, and shall be marked as the Identification article of this standard requires.
11.2.4 The AC disconnecting means of a system interconnected on the supply side of the service disconnect shall be listed as suitable for use as service equipment.

11.3 Interconnection Application

11.3.1 The responsibility for the utility interconnection application shall be as indicated in the datasheet.
Interconnection Application Responsibilityradio
○ The Contractor prepares and files the application in the Owner's name and carries it to permission to operate
○ The Owner or the Engineer files the application and the Contractor furnishes the technical data and the as-built documents
NOTE The Contractor filing the application is the arrangement of a design-build project and puts the party that controls the schedule and the equipment data in contact with the utility; the Owner or the Engineer filing is the arrangement of a design-bid-build project where the application precedes the award and the Contractor inherits a conditional approval. Both are routine, so the field carries no default. (11.3.2)
11.3.3 The interconnection application shall be filed at the earliest date the equipment data permits, and the Contractor shall report to the Engineer of Record within five working days any utility requirement that changes the equipment, the settings, the export limit, or the point of interconnection from the reviewed submittals.
NOTE The utility's study and approval run from weeks on a small system to a year or more on a large one or on a constrained circuit, and the interconnection, not the construction, is what sets the date the array produces; a project that files late discovers the circuit's hosting capacity after the inverters are on the wall. (11.3.4)

12 Mounting System

12.1 Mounting Type

12.1.1 The mounting type of the array shall be as indicated in the datasheet.
Mounting Typeselect
Roof, mechanically attached through the roof covering
Roof, ballasted, no penetrations
Roof, ballasted with supplementary attachments
Roof, standing-seam clamps
Ground mount, fixed tilt
Ground mount, single-axis tracker
Carport or canopy
NOTE A mechanically attached roof array is the lightest, holds on any slope, and puts a flashed penetration through the roof at every attachment, each one needing the roofing manufacturer's acceptance to keep the roof warranty in force; a ballasted array penetrates nothing and holds by weight, which adds 3 to 6 psf of dead load, more at the array edges and corners, requires a roof slope of a few degrees or less and a membrane that tolerates the bearing of the ballast trays, and in a high seismic category or a high wind zone needs more weight than many roofs carry; a ballasted array with a few attachments trades some penetrations for most of the weight and is the arrangement where the structure carries neither alone; standing-seam clamps hold without penetrating or ballasting, with the panel and the seam carrying every load, and are the arrangement wherever that roof exists; a fixed-tilt ground mount costs the land, the foundations, and the fence, and nothing on the roof; a single-axis tracker follows the sun east to west, yields 15 to 25 percent more energy than fixed tilt at the latitude of most of the country, and adds motors, controllers, a wind stow, and maintenance; a carport or canopy shades the parking, carries the highest structure cost per watt, and is built where the roof is unavailable and the land is already paved. The type follows the site and the structure, so the field carries no default. (12.1.2)
12.1.3 The mounting system shall be installed within the limits of its UL 2703 listing and its delegated design for module orientation, clamp location within the module's clamp zone, span, tilt, and ballast or attachment quantity, and no module shall be clamped outside the zone its load rating was established in.
12.1.4 The array and its equipment shall be kept clear of the fire-service pathways, the setbacks, the smoke ventilation areas, and the roof access the adopted fire code requires on the roof, as indicated on the array layout plan, and the pathways shall remain clear of conduit, cable, and combiner boxes.
NOTE IFC Section 1205 and NFPA 1 Section 11.12 set the perimeter pathways, the ridge setbacks, the access aisles through a large array, and the ventilation opportunities a roof keeps clear so that the fire department can reach and vent the roof with the array in place, and the widths and the array size thresholds in them are the fire code's rather than a project selection; a layout that fills the roof to the parapet is the most frequent cause of a fire plan review rejection. (12.1.5)

12.2 Attached Roof Mounting

12.2.1 Where the array is mechanically attached, each attachment shall be fastened to the structural framing or the structural deck as the delegated design states, through a flashed penetration or a curb constructed under Membrane RoofingMembrane RoofingResolves to the current adopted revision.sync/membrane-roofing for a membrane roof and under the standard for the roof covering in place for another, and no attachment shall be fastened to the deck alone unless the delegated design and the structural engineer of record accept it.
12.2.2 The attachment flashing, the sealant, and the penetration detail shall be those the roofing manufacturer accepts in writing for the roof covering in place, and the acceptance shall state that the roof warranty remains in force with the array installed.
12.2.3 The attachment layout shall be as indicated on the delegated mounting design drawings, and an attachment moved in the field to clear a purlin, a drain, or a seam shall be relocated only within the tolerance the delegated design states.

12.3 Ballasted Roof Mounting

12.3.1 Where the array is ballasted, the ballast shall be the blocks the delegated design specifies by weight and location, placed in the trays the racking listing provides, and the installed ballast shall be verified block by block against the ballast plan before the modules are set.
12.3.2 A ballasted system shall be set on a slip sheet or protection pad compatible with the roof membrane as the roofing manufacturer requires, and the roofing manufacturer's acceptance shall cover the pad, the ballast weight, and the point loads at the tray feet.
12.3.3 Where Seismic Design CategorySeismic Design CategoryParameterEach project supplies its own value.seismic-design-category is D, E, or F, an unattached ballasted array shall comply with the displacement-based provisions of ASCE/SEI 7 Section 13.6.12 for unattached rooftop solar arrays, with the clearances to the roof edge, the parapet, the equipment, and the pathways that the calculated displacement requires, or the array shall be attached.
NOTE Ballast holds an array still only until the wind or the earthquake moves it, and an array that slides a foot in a seismic event takes its wiring with it; ASCE/SEI 7 permits an unattached array in the higher categories only where the calculated slide is kept inside a clear zone, which is why the clearance to every edge and obstruction is part of the delegated design and not a field adjustment. (12.3.4)

12.4 Standing-Seam Roof Mounting

12.4.1 Where the array is mounted on a standing-seam metal roof, the clamps shall be listed for the specific seam profile and panel gauge, shall not penetrate the panel, and the confirmation that the seam and the panel carry the clamp reactions shall be obtained under Metal Roof PanelsMetal Roof PanelsResolves to the current adopted revision.sync/metal-roof-panels before the racking is ordered.
12.4.2 The clamp spacing and the clamp torque shall be as the delegated design and the clamp manufacturer's instructions state for the seam profile, and the clamps shall accommodate the thermal movement of the panels without loosening.

12.5 Ground Mounting

12.5.1 Where the array is ground-mounted, the foundation type shall be as indicated in the datasheet.
Ground-Mount Foundation Typeselect
Driven steel pile
Helical pile
Ground screw
Drilled concrete pier
Ballasted precast or cast-in-place footing
NOTE A driven steel pile is the lowest-cost foundation in soil that takes a pile and is set by a machine at a rate of hundreds a day; a helical pile is screwed in, has its capacity read from the installation torque, and suits a soil with cobbles or a shallow refusal; a ground screw is a smaller helical for lighter racking; a drilled concrete pier suits rock or a soil that will not hold a pile, at the highest cost per foundation; a ballasted footing sits on the surface and is the foundation of a landfill cap, a brownfield, or a site where driving is prohibited. The type follows the geotechnical report, so the field carries no default, and the foundations as constructed are governed by Deep FoundationsDeep Foundations (Piles and Drilled Piers)Resolves to the current adopted revision.sync/deep-foundations for the piles and piers and by Concrete PadsConcrete Equipment PadsResolves to the current adopted revision.sync/concrete-pads for a cast-in-place footing. (12.5.2)
12.5.3 The foundations shall be designed under the delegated design from a geotechnical report for the site and from a pull-out and lateral load test program on test piles at the site where the delegated design requires one, with the embedment set below Frost DepthFrost DepthParameterEach project supplies its own value.frost-depth where frost heave governs.
12.5.4 A single-axis tracker shall stow at the wind speed its listing and delegated design state, shall carry a backup power source or a mechanical lock that stows it on loss of power, and shall be furnished with the controller, the sensors, and the communication to the monitoring system that report its position and its faults.
12.5.5 The ground-mount array shall be enclosed by fencing constructed under Fencing And GatesFencing and GatesResolves to the current adopted revision.sync/fencing-and-gates where the drawings so indicate, with the clearance between the fence and the array that the delegated design and NFPA 70 110.26 require, and the equipment pads, the vegetation management, and the grading beneath the array shall be as indicated on the civil site plan.

12.6 Carport and Canopy Mounting

12.6.1 Where the array is mounted on a carport or canopy, the structure shall be designed and constructed under Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing for the array loads of the delegated design, with the clear height, the column protection, and the lighting indicated on the site plan and the structural drawings, and the racking, the modules, and the wiring shall comply with this standard.
12.6.2 The wiring beneath a canopy shall be concealed within the structure or in raceway, protected from vehicle impact to a height of 8 ft above the pavement, and arranged so that water shed by the modules is collected and discharged clear of the parking spaces.

13 Bonding of the Array

13.1 The modules, the racking, and every exposed non-current-carrying metal part of the array shall be bonded and connected to the equipment grounding conductor in accordance with NFPA 70 690.43 and Article 250, by the method indicated in the datasheet.
Module and Racking Bonding Methodradio
● Integrated bonding through the UL 2703 listed clamps and splices, with a listed ground lug per row
○ Separate bonding jumper and equipment grounding conductor to every module and rail
NOTE A UL 2703 racking system whose clamps and splices are listed as bonding devices bonds the module frames and the rails to one another through the clamps themselves, so that one equipment grounding conductor connection per row through a listed lug grounds the whole row, and it is the method of nearly every framed-module installation, which is why the field defaults to it; a separate jumper to every module and rail is the method of a racking whose clamps are not listed for bonding, of a frameless module, and of an Owner who requires a visible conductor, at the cost of a lug and a jumper at every module. (13.2)
13.3 Where integrated bonding is selected, the clamps, the splices, and the ground lugs shall be the listed bonding components of the racking system installed at the torque the listing states, and the bonding path shall not depend on a component the listing does not name as a bonding device.
13.4 The equipment grounding conductor of each source and output circuit shall be sized under NFPA 70 690.45 and 250.122, shall run with the circuit conductors, and shall be connected to the grounding electrode system of the building or the structure as Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding requires, with any auxiliary electrode at the array furnished under that standard.
13.5 Where the racking is on a standing-seam roof or a structure that is itself bonded to the lightning protection system, the bonding between the array and that system shall be as Lightning ProtectionLightning Protection SystemsResolves to the current adopted revision.sync/lightning-protection requires.

14 Metering and Monitoring

14.1 Production Metering

14.1.1 The production of the photovoltaic system shall be metered as indicated in the datasheet.
Production Meteringradio
○ Revenue-grade meter on the inverter output, ANSI C12.1 accuracy class
○ Production reported by the inverters alone
○ Production meter furnished by the serving utility or the incentive program
NOTE A revenue-grade meter on the inverter output records the production independently of the inverters and is what settles a production guarantee, an incentive payment, a renewable energy certificate, or a power purchase agreement, at the cost of a meter and its current transformers; inverter-reported production is accurate to a few percent and costs nothing, and it is unverifiable by a third party and lost when an inverter is replaced; a utility or program meter is furnished and read by the party that pays and is the arrangement of a feed-in or performance-based incentive. The arrangement follows who pays for the energy, so the field carries no default, and the meter as a product is governed by Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring. (14.1.2)
14.1.3 Where a revenue-grade meter is selected, it shall comply with Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring for the accuracy class, the current transformers, and the communications, shall be read by the monitoring system, and shall be the instrument the performance acceptance test and the production guarantee are settled against.

14.2 Monitoring Granularity

14.2.1 The monitoring system shall record the production and the status of the system at the granularity indicated in the datasheet.
Monitoring Granularityradio
○ Inverter level
○ String level
○ Module level
NOTE Inverter-level monitoring reports the output and the faults of each inverter and finds a failed inverter the same day and a failed string never; string-level monitoring reads the current of each string at the inverter input or the combiner and finds a failed string, an open fuse, or a shaded row by comparison with its neighbors, and it is what a commercial array of any size is maintained from; module-level monitoring comes with optimizers and microinverters and finds a single degraded module, at the cost of those devices and the data they generate. The granularity follows the architecture and the maintenance organization, so the field carries no default. (14.2.2)
14.2.3 The monitoring system shall record, at an interval of fifteen minutes or shorter, the AC energy and power of each inverter, the DC voltage and current of each input at the granularity selected, the inverter status and every fault code, the production meter reading where a meter is furnished, and the sensor readings selected under this standard, and shall retain the data for not less than the production guarantee term or five years, whichever is longer.
14.2.4 The monitoring system shall alarm by electronic message to the Owner's designated recipients on an inverter fault, a ground fault, an arc fault, a rapid shutdown operation, a communication loss exceeding one hour, and a daily production below a threshold the Owner sets, and the alarm configuration shall be demonstrated at commissioning.

14.3 Monitoring Instruments

14.3.1 The monitoring system shall be furnished with the instruments indicated in the datasheet, installed in accordance with IEC 61724-1 for the monitoring class the performance acceptance method selected under this standard requires.
Monitoring Instrumentscheckbox
☐ Plane-of-array irradiance sensor
☐ Reference cell of the module technology furnished
☐ Module back-of-cell temperature sensor
☐ Ambient temperature sensor
☐ Wind speed sensor
☐ Soiling measurement
NOTE A plane-of-array irradiance sensor and a module temperature sensor are what turn a production figure into a performance ratio, and without them a low month cannot be told from a cloudy one; a reference cell of the same technology as the modules responds to the spectrum and the angle as the modules do and is the instrument IEC 61724-2 settles a capacity test with; ambient temperature and wind speed feed a model that predicts the module temperature; a soiling measurement separates dirt from degradation on a dusty or agricultural site. A production guarantee cannot be settled without the first two, which is why they are selected wherever a guarantee is. (14.3.2)

14.4 Communications

14.4.1 The monitoring system shall communicate with the Owner's systems by the interfaces indicated in the datasheet.
Monitoring Interfacescheckbox
☑ Manufacturer-hosted monitoring portal with Owner administrator access
☐ Modbus TCP or SunSpec Modbus to the building automation system
☐ IEEE 2030.5, IEEE 1815, or SunSpec Modbus interface to the serving utility as the interconnection agreement requires
☐ Data export by open application programming interface to a third-party platform
NOTE The inverter manufacturer's portal is the interface every system ships with and the one the warranty and the production guarantee are read through, which is why it is the default; a Modbus connection lets the building automation system display and log the production under Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system; the utility interface is the one IEEE 1547 requires an interactive resource to present where the utility uses it; an open interface lets an Owner with a portfolio read every site into one platform. (14.4.2)
14.4.3 The monitoring gateway and the inverters shall support authenticated and encrypted communication, shall be placed on a network segment the Owner controls behind a gateway the Owner administers, and the manufacturer's remote access shall be logged and revocable by the Owner, with the network cabling under Structured CablingStructured Cabling SystemsResolves to the current adopted revision.sync/structured-cabling.

15 Identification

15.1 Every label, placard, and marking this article requires shall be permanent, weather-resistant, and legible for the life of the system, of the material, lettering, and attachment Equipment LabelingElectrical Equipment LabelsResolves to the current adopted revision.sync/equipment-labeling requires, and red with white lettering where NFPA 70 690.56 requires that color.
15.2 A rapid shutdown placard shall be installed at the service equipment and at each initiation device in accordance with NFPA 70 690.56(C), stating the type of rapid shutdown furnished and the conductors it controls, with the diagram and the wording the adopted edition requires, and each initiation device shall be labeled as the rapid shutdown switch for the solar PV system.
15.3 A permanent plaque or directory shall be installed at the service equipment and at each point of interconnection in accordance with NFPA 70 705.10, identifying every power source on the premises and the location of every disconnecting means, with the plaque furnished under Equipment LabelingElectrical Equipment LabelsResolves to the current adopted revision.sync/equipment-labeling.
15.4 Each DC photovoltaic circuit disconnecting means and each combiner shall be marked in accordance with NFPA 70 690.53 with the maximum circuit voltage and the maximum circuit current, as calculated under this standard for the adopted edition, and the disconnecting means shall be marked as the photovoltaic system disconnect in accordance with 690.13.
15.5 The point of interconnection shall be marked in accordance with NFPA 70 690.54 with the rated AC output current and the nominal operating AC voltage of the system.
15.6 A backfed breaker at a load-side interconnection shall be marked in accordance with NFPA 70 705.12 to warn that it is a power source output connection and is not to be relocated, and the equipment it is installed in shall be marked with the sum of the ratings of the sources connected to its bus.
15.7 DC raceways, cable trays, enclosures, and junction boxes inside a building shall be marked in accordance with the provisions of NFPA 70 690.31 for DC circuits on or in a building, at intervals not exceeding 10 ft, on every section separated by a wall or a ceiling, and on every enclosure, with the warning that identifies a photovoltaic power source.
15.8 Each inverter, combiner, and disconnect shall carry a nameplate stating its designation on the one-line diagram, the circuits it serves, and the location of its source, and the arc-flash warning label required under Arc Flash StudyArc-Flash StudyResolves to the current adopted revision.sync/arc-flash-study where the study covers the AC equipment.
15.9 Where the system is multimode or is paired with storage, the disconnecting means and the service equipment shall carry the additional markings of NFPA 70 Article 706 and 705.10 for the storage, as Battery Energy Storage SystemsBattery Energy Storage SystemsResolves to the current adopted revision.sync/battery-energy-storage-systems requires.

16 Testing

16.1 Commissioning Tests

16.1.1 The photovoltaic system shall be commissioned in accordance with IEC 62446-1 and this standard after installation is complete and before it is operated in parallel with the utility, and the commissioning shall include the tests indicated in the datasheet.
Commissioning Testscheckbox
☑ Continuity of the equipment grounding and bonding of every module row and enclosure
☑ Polarity of every source and output circuit
☑ Open-circuit voltage of every source circuit with irradiance and temperature recorded
☑ Operating or short-circuit current of every source circuit with irradiance recorded
☑ Insulation resistance of every DC circuit
☑ Functional test of every inverter, disconnect, ground-fault and arc-fault function, and alarm
☑ Rapid shutdown operation and timing from every initiation device
☑ Anti-islanding and IEEE 1547 settings verification, witnessed by the utility where it requires
☐ Current-voltage curve trace of every source circuit
☐ Infrared thermography of the modules, the connectors, and the terminations under load
☑ Torque verification of terminations
☑ Monitoring and production meter data verification against field readings
NOTE The default set is the Category 1 test sequence of IEC 62446-1, which every grid-connected system receives, plus the rapid shutdown and the utility tests NFPA 70 and the interconnection agreement add; the curve trace and the thermography are the Category 2 tests, added on a system large enough that a string a few percent low or a connector a few degrees warm is worth finding on the first day rather than in the first year. (16.1.2)
16.1.3 Open-circuit voltage and current readings shall be taken with the irradiance and the module temperature recorded at the time of each reading, corrected to standard test conditions, and compared string to string, and a string whose corrected voltage or current departs from the mean of its group by more than 5 percent shall be investigated and the cause corrected before acceptance.
16.1.4 The insulation resistance of each DC circuit shall be measured at the test voltage IEC 62446-1 states for the system voltage, with the modules connected and the inverter and the surge protective devices isolated, and shall be not less than the minimum IEC 62446-1 states for the array size.
16.1.5 The rapid shutdown test shall operate each initiation device in turn, measure the voltage at the array boundary and within it at the time limit, and confirm that every inverter and every system on the building responded, and the test shall be repeated after any change to the inverters or the module-level devices.
16.1.6 The commissioning tests shall be performed by the party indicated in the datasheet.
Commissioning Test Performerradio
○ Independent testing firm qualified under the acceptance testing standard
○ Installing contractor's own technicians, with the inverter manufacturer's commissioning service for the inverters
NOTE An independent firm reports against a published standard with no stake in the result and is what a financed system or a production guarantee is accepted on; the installing contractor's own technicians, with the inverter maker commissioning its own equipment, is the arrangement of most small and mid-size systems and costs the project only the day. Which the Owner wants follows the size of the system and who is relying on the report, so the field carries no default, and the AC equipment at the point of interconnection is tested under Electrical Acceptance TestingElectrical Acceptance TestingResolves to the current adopted revision.sync/electrical-acceptance-testing in either case. (16.1.7)
16.1.8 A circuit, an inverter, or a function that fails a commissioning test shall not be placed in service, the Contractor shall report the failure to the Engineer of Record within one working day with the measured values, and the cost of the correction and of every repeated test shall be borne by the Contractor.

16.2 Performance Acceptance

16.2.1 The performance of the photovoltaic system shall be accepted by the method indicated in the datasheet.
Performance Acceptance Methodradio
○ Commissioning tests only, no performance test
○ Capacity test in accordance with IEC 61724-2 after commissioning
○ Energy performance evaluation in accordance with IEC 61724-3 over the first twelve months
NOTE The commissioning tests prove that every circuit works and say nothing about whether the array produces what the energy model promised; a capacity test under IEC 61724-2 measures the power at a measured irradiance and temperature over a few clear days after commissioning and compares it with the model at the same conditions, which settles the installed capacity before final payment; an energy evaluation under IEC 61724-3 compares the metered energy over a year with the model run on the measured weather, which settles the production guarantee and catches a soiling, a shading, or an availability loss a capacity test cannot see. The method follows whether a production guarantee is carried, so the field carries no default. (16.2.2)
16.2.3 Where a capacity test is selected, the measured capacity corrected to the reference conditions shall be not less than the percentage of the modeled capacity indicated in the datasheet, and a system that measures below it shall be corrected and retested at the Contractor's cost or the shortfall settled as the Contract provides.
Capacity Test Acceptance, Measured as a Percentage of Modeled Capacityrange
Not less than
%
90100
NOTE The modeled capacity is the design value and the installed array is expected to reach it, and an acceptance below 100 percent recognizes the uncertainty of the irradiance sensor, the temperature correction, and the meter, which together run a few percent; where the threshold is set depends on how the project treats that uncertainty, so the field carries no default. (16.2.4)

16.3 Owner Training

16.3.1 The Contractor shall conduct training for the Owner's operating staff before substantial completion, of the duration indicated in the datasheet, covering the monitoring portal and its alarms, the normal and the emergency shutdown of the system including rapid shutdown, the restart after a utility outage or a fault, the isolation of a string for service, the cleaning and the inspection schedule the warranties require, and the records the production guarantee requires the Owner to keep.
Owner Training Durationrange
Not less than
hours
216
NOTE Two hours covers a string-inverter array whose operation is a portal and whose maintenance is an annual inspection; a day covers a tracker array, a central inverter, or a multimode system with an island mode the Owner's staff will operate. The duration follows the system, so the field carries no default. (16.3.2)

17 Installation

17.1 Array Installation

17.1.1 Modules shall be handled by their frames or by the edge-lift the manufacturer specifies for a frameless module, shall not be walked on, stood on, or used as a work surface, shall not be set down on a corner, and shall not be lifted or carried by their junction boxes, leads, or connectors.
NOTE A cell cracks under a boot and keeps producing, and the crack opens over a few winters until the string is a few percent low and the module is out of warranty for mishandling; the damage is invisible on installation day and is seen later only by electroluminescence, which is why handling is a requirement and not a care note. (17.1.2)
17.1.3 Modules shall be installed in the orientation and the clamp zones the module listing and the delegated design permit, with the clamp torque the racking manufacturer states and verified with a calibrated tool, and the module serial numbers shall be recorded by position before the modules are covered by the next row.
17.1.4 The work on a roof shall be performed with the fall protection OSHA 29 CFR 1926 Subpart M requires, and the anchors that remain for the Owner's maintenance shall be furnished under Fall Protection AnchorageRoof and Facade Fall Protection AnchorageResolves to the current adopted revision.sync/fall-protection-anchorage.
17.1.5 The roof covering, the flashing, the drains, and the walkway pads shall be protected during the installation, and damage to the roof covering caused by the photovoltaic work shall be repaired by the roofing contractor under the roofing manufacturer's details at the Contractor's cost.
17.1.6 Roof penetrations shall be flashed and sealed by the roofing contractor or by an installer the roofing manufacturer accepts, under the roofing standard for the covering in place, and no attachment shall be made until the roofing manufacturer's written acceptance under the Informational Submittals article is in hand.

17.2 Electrical Installation

17.2.1 Every conductor termination shall be torqued to the manufacturer's published value with a calibrated torque tool in accordance with NFPA 70 110.14(D), and the values applied shall be recorded in the commissioning report.
17.2.2 Source circuits shall be connected to the inverter or the combiner only after the polarity and the open-circuit voltage of each have been measured and recorded, and no DC connector shall be opened or closed under load.
17.2.3 The inverters shall be mounted at the height, the spacing, and the clearance from the roof, the wall, and each other that the manufacturer's instructions require for cooling, shaded from direct sun where the manufacturer so requires, and with the working space of NFPA 70 110.26 in front of every enclosure the disconnects or the fuses are serviced from.
17.2.4 The DC and the AC conductors beyond the array, the raceways, the supports, and the penetrations shall be installed under Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables, Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit, and, below grade, Underground DuctbankUnderground Electrical Duct BanksResolves to the current adopted revision.sync/underground-ductbank, with the rooftop raceways supported clear of the roof surface and the expansion fittings the raceway standard requires.
17.2.5 The system shall not be energized or operated in parallel with the utility until the commissioning tests this standard names for energization have passed, the Authority Having Jurisdiction has inspected the installation, and the utility's permission to operate is in hand.

18 Delivery, Storage, and Handling

18.1 Modules shall be delivered on the manufacturer's pallets in the manufacturer's packaging, with the flash test data and the serial numbers of each pallet, and shall be inspected at receipt for broken glass, damaged frames, damaged connectors, and conformance with the reviewed submittal.
18.2 Module pallets shall be stored upright on a level surface, protected from rain and standing water, strapped against wind, and not stacked higher than the manufacturer permits, and modules removed from a pallet shall be stored on edge in the manufacturer's orientation and not laid flat.
18.3 Inverters, module-level electronics, and monitoring equipment shall be stored within the manufacturer's published temperature and humidity range, off the ground, and protected from construction dust and water until installed, and an inverter stored outdoors shall be in its sealed packaging or installed on its mount with its covers closed.
18.4 Racking shall be stored off the ground and sorted by component, and galvanized or anodized components shall be protected from standing water and from contact with dissimilar metals during storage.
18.5 A module with broken glass, a cracked backsheet, a damaged connector, or a frame deformed enough to open the glass edge seal shall be rejected and removed from the site, and shall not be installed or kept as a spare.

19 Warranty and Production Guarantee

19.1 Module Warranties

19.1.1 The module manufacturer shall warrant the modules against defects in materials and workmanship for not less than the term indicated in the datasheet, measured from the date of substantial completion.
Module Product Warranty Termrange
Not less than
years
1030
19.1.2 The module manufacturer shall warrant the power output of the modules for not less than the term indicated in the datasheet, with the power at the end of the term not less than the percentage of nameplate power indicated in the datasheet and a linear or stepped degradation schedule between.
Module Performance Warranty Termrange
Not less than
years
2030
Default: 25 years
Module Power Retained at the End of the Performance Warrantyrange
Not less than
% of nameplate
8095
NOTE A twenty-five-year performance warranty is the term nearly every module is sold with, which is why that field defaults to it, and thirty years is offered on glass-glass product lines; the product warranty, which covers the module failing rather than fading, has moved from ten or twelve years to fifteen or twenty-five on the common product lines and has no single norm, so that field carries none. The retained power follows the technology: a passivated emitter module is warranted in the low to mid eighties at twenty-five years, a tunnel oxide module in the upper eighties, and a heterojunction or glass-glass module near ninety, so that field carries no default either. (19.1.3)
19.1.4 The module warranties shall be registered in the Owner's name, shall be transferable to a subsequent owner of the building, and shall not be conditioned on a maintenance more frequent than an annual inspection and a cleaning when soiling is observed.

19.2 Inverter, Electronics, and Racking Warranties

19.2.1 The inverter manufacturer shall warrant the inverters and the module-level electronics against defects in materials and workmanship for not less than the term indicated in the datasheet, with the coverage indicated in the datasheet.
Inverter Warranty Termrange
Not less than
years
525
Inverter Warranty Coverageradio
○ Parts
○ Parts and on-site labor
NOTE String inverters are sold with five or ten years and an extension to fifteen or twenty for a price, microinverters and optimizers with twenty-five years to match the modules, and central inverters with five years and a service contract, so the term follows the architecture and the field carries no default; a parts warranty ships the replacement and leaves the Owner to pay the technician, which suits an Owner with a maintenance contract, and a parts and labor warranty brings the manufacturer to the roof, which suits an Owner with no one trained on the equipment. Neither coverage is the norm, so that field carries no default. (19.2.2)
19.2.3 The racking manufacturer shall warrant the racking, its finish, and its bonding components against defects and against corrosion for not less than the term indicated in the datasheet.
Racking Warranty Termrange
Not less than
years
1025

19.3 Installation Warranty

19.3.1 The Contractor shall warrant the installation, including every termination, connector, attachment, flashing by the photovoltaic work, and the results of the commissioning tests, for not less than the term indicated in the datasheet, and shall correct a defect in it, including a roof leak at a photovoltaic attachment, at no cost to the Owner.
Installation Warranty Termrange
Not less than
years
110
19.3.2 A component or a module replaced under warranty shall be warranted for the remainder of the original term or for one year from the date of replacement, whichever ends later, and a replacement module shall be matched in electrical characteristics to the string it joins as the manufacturer's instructions require.
19.3.3 The roofing warranty shall remain in force with the array installed, and where a roof leak occurs at a photovoltaic attachment, the Contractor shall bear the cost of the investigation and the repair unless the roofing contractor's work under its own details is shown to be the cause.

19.4 Production Guarantee

19.4.1 The production guarantee carried by the Contractor shall be as indicated in the datasheet.
Production Guaranteeradio
○ No production guarantee beyond the equipment warranties
○ Energy production guarantee by the Contractor for the term and the percentage indicated
NOTE A production guarantee makes the Contractor answer for the energy the model promised, settled annually against the revenue-grade meter and the measured weather, and it is the instrument a financed system, a power purchase agreement, or an Owner who bought on a payback requires; without one the Owner holds the equipment warranties and the energy model as a prediction. Whether one is carried follows how the system is financed, so the field carries no default, and a guarantee cannot be settled without the production meter and the irradiance and temperature instruments selected under this standard. (19.4.2)
19.4.3 Where a production guarantee is selected, the guaranteed annual energy shall be not less than the percentage of the modeled annual production indicated in the datasheet, weather-corrected under IEC 61724-3, for the term indicated in the datasheet, and the shortfall shall be settled as the Contract provides.
Production Guarantee Termrange
years
110
Guaranteed Annual Energy as a Percentage of Modeled Productionrange
Not less than
%
80100
NOTE The modeled figure is a fifty percent probability of exceedance, so a guarantee at 100 percent of it is missed half the time by a perfect system; guarantees are written at 90 to 95 percent of the model for the uncertainty of the weather correction, the soiling, and the availability, and over terms of two to five years in construction contracts and up to the financing term in a power purchase agreement. Both values follow the financing, so neither field carries a default. (19.4.4)

20 Spare Parts

20.1 The spare part types to be delivered with the system shall be as indicated in the datasheet.
Spare Part Typescheckbox
☐ Modules of the model installed
☑ DC connectors of the series installed, with the crimp tool and die
☑ Photovoltaic fuses of each rating installed
☐ Module-level electronic devices or rapid shutdown devices of each type installed
☐ Racking clamps, bonding components, and ground lugs
☐ Inverter fans, filters, and surge protective device modules
☐ Monitoring gateway and sensors
20.2 The number of spare modules shall be as indicated in the datasheet, as a percentage of the installed module count, rounded up to a whole module.
Spare Modulesrange
% of installed modules
0.5125
NOTE A module model is in production for two or three years and a replacement bought later is a different module, with a different voltage and current that mismatch the string and a different frame that often does not fit the clamps, which is why spares of the installed model are bought with the array; one percent covers the breakage of a decade on most arrays, and a zero records that the Owner accepts a mismatched replacement or a reconfigured string. The connectors and the fuses are the spares that are used, and the crimp tool is what keeps a replacement connector in the listed series. No quantity is the norm, so the field carries no default. (20.3)
20.4 Spare modules shall be stored by the Owner in the manufacturer's packaging, on edge, indoors, and the Contractor shall deliver them with a written storage instruction and obtain a signed receipt.
20.5 Spare parts shall be identical to and interchangeable with the installed parts, shall be the parts the manufacturers list for the system, and shall be delivered in their original packaging and labeled with the equipment they serve.

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"Photovoltaic Systems," SynC Standards, revision 4. Licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://synergyinconstruction.com/standards/general/photovoltaic-systems. Reference material only; not professional engineering advice and provided without warranty. Verify against governing codes and have a licensed professional review before use.