Rapid Shutdown – Everything Solar Installers Should Know

The update of 2017 of the NEC (National Electric Code) is now law in 30 states in the country as of NEC January 2020. The remaining states are currently in the process of adding the new rules to their current legislation.

By complying with the NEC of 2017, this means that any solar installation on any building must have the proper capacity of being able to quickly shut down in case of an emergency. This is known as module-level rapid shutdown.

These rule applies to PVs mounted on buildings, but it does not include solar carports because they are not considered buildings. Instead, solar carports are considered to be shelters.

There are several ways that solar installers can ensure that they are in compliance with the 2017 NEC.

Install A Field Labeled Or Listed Rapid Shutdown System

‘Listed’ is a term that derived from the first name that was given to the UL’s certification program that was developed over 100 years ago. The NEC uses this term, but it does not mention any systems or products that must have UL certification.

The rule instead discusses the types of organizations that would be able to perform this type of certification service. It has been suggested that manufacturers certify their products so they will be able to meet the rapid shutdown specifications given by UL. However, other testing labs that are nationally recognized could possibly be alternatives.

During the Solar Power International Conference in 2019, there were many rapid shutdown device and inverter manufacturers present that displayed their certifications with SunSpec. Even though SunSpec has developed specific protocols that allow for communication with different types of rapid shutdown equipment, it is not like UL. It is not a listed body.

The Installation Of A BIPV System That Does Not Have Metal Parts, No Conductors Exposed And More Than 8 Feet Of Grounded Metal

Solar tiles, shingles and other types of BIPV (PV)integrated systems meet the 2017 NEC requirements only if they do not have any metal parts, they are not located near grounded metal or have any exposed conductors. These systems must remain separate from any components that are conductive and grounded.

Install A Solar Energy System That Is Able To Reduce Its Voltage To 80 V Within A Minute

Microinverters are usually compliant with the rapid shutdown rule because they are able to change high-voltage power into low-voltage power in less than a minute. The lower voltage power is able to go down to around 80-V in less than half of a minute.

On the other hand, the NEC of 2017 does not mention microinverters specifically when discussing ways to be in compliance with rapid shutdown requirements.

There are some microinverters that have been designed to have capacitators that are located on the front part of the circuitry. This means that unless there is a voltage measurement done by an experienced inspector, it will be difficult to know if the microinverter is really under the 80-V restriction.

UL has been performing these types of tests regularly in order to provide verification as to whether specific microinverters are able to meet the threshold set by the NEC of 80-V. However, it is difficult to assess the information from this type of testing after the inverters are installed.

A revised edition of the NEC that is scheduled to be released in 2020, it will likely focus less on previous rules and focus more on the requirements for rapid shutdown.

So, is rapid shutdown the same as total shutdown? And how fast is rapid? Rapid shutdown is not an entire shut down of the system. This is why ‘PV Hazard Control’ was created as a way to help consumers better understand what is really being accomplished when discussing that type of protection.

Understanding the different necessities that are in place for solar installation in a certain jurisdiction is an ideal starting point to ensure that you will have a successful installation that is approved by the governing agency in the area.



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