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Code compliance with Fronius

Our solutions for compliance

We are committed to making sure that all our solutions are fully compliant with the latest codes and standards. Furthermore, our engineers are pro-actively involved in industry standardization groups.

NEC 2014 – Rapid Shutdown

All Fronius SnapINverters are compliant with the NEC 2014 (690.12) and NEC 2017 (Array Disconnect) compliance code requirements. We are proud to offer a bankable solution to the latest National Electrical Code (NEC) requirements of Rapid Shutdown function (NEC 690.12) on rooftop photovoltaic systems. The Fronius Rapid Shutdown Box ensures NEC 2014 (690.12) compliance code compliance while enhancing rooftop and firefighter safety, quality, reliability and the most seamless solution available on the market.

NEC 2017 – Module Level Shutdown


To offer solar installers an easy plug-and-play solution for the NEC 2017 module level shutdown requirement, Fronius believes that the best solutions are based on an industry standard with Power Line Communication (PLC). The SunSpec Communication Signal for Rapid Shutdown provides this standard. This industry standard is a multi-vendor and multi-device communication specification for inverters, modules, and string combiners to support NEC 2014, NEC 2017, and UL 1741 module-level rapid shutdown requirements. 

For more information about the SunSpec Alliance visit their website: 

Fronius Symo Advanced

The Fronius Symo Advanced comes with an integrated Power Line Communication (PLC) transmitter based on the SunSpec Rapid Shutdown communication standard. Solar installers get a simple and cost-effective solution for module level shutdown.   

Rule 21

“Rule 21” refers to the generator interconnection requirements of each CA Investor-Owned Utility (IOU). A years-long process has been underway to update Rule 21 with “smart inverter” requirements in a phased approach. Rule 21 Phase 1 contains the most important autonomous functions that can be set at installation time, and whose settings wouldn’t necessarily change over time. Phase 2 addresses communications requirements. Phase 3 development is ongoing and would address further autonomous functions and communications-based functions. This document only covers Phase 1 in which the timeline and most details have already been defined. Ongoing discussions with the CA IOUs and other stakeholders are addressing remaining Phase 1 implementation issues.

Rule 21 requires inverters to have new functions and a new certification under UL 1741. Inverters receive a new nameplate label that identifies it as a “Grid Support Utility Interactive Inverter.” Besides new firmware, certification and the label, all else remains the same. The following grid support functions are required:

  • / Voltage and frequency ride-through
  • / Set Power Factor
  • / Volt-var
  • / Soft start ramp rate
  • / Normal ramp rate

For more information about Rule 21 visit

Arc Fault Circuit Interrupter (AFCI)

The National Electrical Code (NEC) defines arcs as “arcing faults resulting from a failure in the intended continuity of a conductor, connection, module, or other system component.” To increase fire safety of solar systems, the NEC requires solar systems installed on buildings to be equipped with an Arc Fault Circuit Interrupter (AFCI) (section 690.11 of the NEC) and for the system to visually indicate if an arc occurred. When an arc occurs the NEC requires that the system be restarted manually.


There are various reasons for why an arc can occur. Typical examples for solar installations are:

  • Faulty system components
  • Loose connections
  • Installation errors
  • Physical damage to equipment
  • Damaged conductors
  • Aging


Nowadays, most inverters have an integrated UL certified AFCI to comply with the NEC requirements - including the Fronius SnapINverter generation and Fronius IG Plus Advanced. These features are turned on by default. However, there are also third party solutions available on the market, which are compatible with Fronius product. Your solar installer can choose between the Fronius internal AFCI solution, or an external third-party AFCI solution.


The American National Electrical Code is not a national standard adopted uniformly across the United States. Each state and municipality must individually adopt sections, variations, or additions of the NEC as that state or municipality deems necessary. Your solar installer will work with an Authority Having Jurisdiction (AHJ) to verify the exact PV configuration needed to meet your community’s local standard. The AHJ is the local, state, or federal official designated responsible for approving equipment, installation, or procedure. The local AHJ is responsible for enforcing the local standards at any PV installation site. The Standard for Electrical Safety in the Workplace (NFPA) publishes standards to help provide some guidance as to this person’s roles and responsibilities.

Installers are instructed to follow manufacturer's guidelines for installation and maintenance of the PV components. However, final decisions regarding site specifics components and requirements for individual PV installations, as an industry standard, are the responsibility of those most familiar with the site, your installer and the AHJ.

Practically speaking, the installer is the only entity capable of determining if the combination of component parts that make up a PV installation leaves the site vulnerable to arc flashes.


It's the installer’s responsibility to determine if AFCI is required in your jurisdiction; and if so required whether or not to use the Fronius integrated AFCI feature or a third-party solution. Since the feature is turned on by default, the installer can request a free AFCI Token for deactivating the feature, if the installer so chooses.

Access to this token is not a determination by Fronius that AFCI should or should not be activated on a particular site. The token is simply information, just like our manuals, of options within the inverter. It is still the responsibility of the installer to use appropriate and professional judgement and to follow all industry standards, rules, and regulations of the jurisdiction where the site is located.


Homeowners who acquire a PV system through the purchase of a new home should have an installer check the PV system and to make sure the proper AFCI regulations are being followed.

If you would like to get free access to the AFCI Token, please contact Fronius Technical Support at or (219) 734-5500