NEC Mandatory Code: building PV must have rapid shutdown capability
The 2017 update to the National Electrical Code – NEC requires that all photovoltaic (PV) arrays on buildings have module-level rapid shutdown capabilities in the event of an emergency. Starting in January 2019, 24 states are required to implement PV module-level power control and safety (“rapid shutdown“), with 30 states now in effect, which will affect millions of PV panels and all solar inverters.
The rule applies to any PV installed on a building, and the US National Electrical Code uses the term “Listed”, but does not explicitly state that products and systems must be UL certified, but rather talks about the general characteristics of the units that will perform the certification service.

Therefore, the industry believes that UL believes that manufacturers should certify their products for fast shutdown through UL, but other nationally recognised testing laboratories can also be used.
Sunspec’s listing is equivalent to the product already meeting the requirements of the NEC’s mandatory specifications and being “Listed” for use in the building PV market. And because Sunspec’s approved communication protocols have been authorised for use with the inverters, the inverters have been Reday for the Building, not just lab certified.
In other words, having a UL List listing only proves that the product has this function, it is a passport, not necessarily a Ready for Sale product, but with a Sunspec listing, you must be Ready, not only with this function, but also with the function of the function has been able to communicate with other components, into the practical.

Safe swithes

Rapid shutdown device

What is SunSpec?
The SunSpec Alliance is a consortium of more than 100 PV and energy storage distributed energy industry participants pursuing information standards to enable interoperability of “plug and play” systems. SunSpec standards address the operational aspects of PV power generation and storage plants in the Smart Grid, including residential, commercial and utility-scale systems, to reduce costs, promote technological innovation and accelerate industry growth.

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The SunSpec-certified Rapid Shutdown procedure verifies compliance with the SunSpec Rapid Shutdown Functional Specification’s communication signals, which are tested using the UL 1741 SA standard to meet the requirements of the National Electrical Code (NEC) 2017. The Compliance Option is a limited engineering evaluation after installation in a specific location, and if the installation meets the NEC 2017 requirements, it can be labelled as a fast shutdown system if allowed by the AHJ.String inverters require a “Listed Listed” accessory to comply with fast shutdown requirements, where a transmitter or initiator with fast shutdown functionality is installed into the inverter during the manufacturing process or aftermarket. The transmitter is paired with a sensor connected to the array, and in the event of a fire, a first responder activates the quick shutdown switch or circuit breaker on the inverter, and the transmitter deploys the sensor on the array and stops power.
SunSpec has developed important protocols for the communication between different devices during the fast shutdown process, SunSpec Fast Shutdown is usually implemented with inverters and PV modules, but other configurations are also possible, it guarantees:
First responder safety: providing a simple, reliable solution to shut down module-level voltage to 1V per module (NEC1017 requires <80V);
Industry benefits and growth: the lowest cost solution is a fundamental market need. Reduce installation and interconnection costs with plug-and-play system components. Report on system operation whenever the sun rises or the system is restarted.
Consumer Benefits and Protection: Open standards that protect consumers through competitive pricing, multi-vendor choice, differentiated options and value availability. Ensure system service and upgrades through vendor selection and interoperable components. Increase consumer safety and confidence in DER technology.
Future PV Hazard Controls require rapid shutdown functionality to be fully integrated into the solar system, rather than the current standard requirement of allowing the use of different components that are certified for rapid shutdown.