CODE CORNER: Rapid Shutdown Requirements of the 2014 & 2017 NECs

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The Fronius Rapid Shutdown box is an RS solution for all Fronius SnapINverters in systems up to 600 V.
SolarBOS’s Rapid Shutdown Solution combiner for string inverters provides an RS solution for inverters located more than 10 feet away from the PV array.
SMA’s Rapid Shutdown System provides RS compliance for systems using Sunny Boy inverters, and allows continued use of the inverter’s Secure Power Supply feature when the grid is down.

Many jurisdictions are adopting and enforcing new electrical codes. In some locations, such as Massachusetts, this means jumping on board with the 2017 National Electrical Code (NEC), the most up-to-date version. Other locations, like California, are using the 2014 NEC as the new code. If you are unsure which code your jurisdiction is using, you can look it up on a NEMA map (see bit.ly/NEMAmap) or contact your local permitting office. Additionally, many states use the NEC as a model, but have amendments modifying some language.

Since the majority of states now use either 2014 or 2017, you’ll be seeing the implementation of one of the most contentious sections in Article 690—rapid shutdown (RS). In the previous “Code Corner,” Brian Mehalic introduced the changes for 2017. Given the different versions that have been implemented across the country and the varying levels of understanding on all the requirements, this article details RS in the 2014 and 2017 editions.

The intent of the 690.12 RS requirement is to remove PV system shock hazards to individuals, particularly firefighters. This is given further attention in 2017 with added language in the introductory sentence.

Section 690.12, “Rapid Shutdown of PV Systems on Buildings,” was introduced in the 2014 NEC. This requirement applies only to PV systems with AC or DC circuits located on or in a building. The section consists of five requirements for controlling conductors:

(1)        Requirements for controlled conductors shall apply only to PV system conductors of more than 1.5 m (5 ft.) in length inside a building, or more than 3 m (10 ft.) from a PV array.

(2)        Controlled conductors shall be limited to not more than 30 volts and 240 volt-amperes within 10 seconds of rapid shutdown initiation.

(3)        Voltage and power shall be measured between any two conductors and between any conductor and ground.

(4)        The rapid shutdown initiation methods shall be labeled in accordance with 690.56(B).

(5)        Equipment that performs the rapid shutdown shall be listed and identified.

Many installers have pointed out that the lack of more concrete requirements—such as a location for the RS controller—allow multiple interpretations. As for the last requirement, that “equipment that performs the rapid shutdown shall be listed and identified,” there’s currently no RS standard for equipment manufacturers to follow. This leaves installers often asking, “Listed and identified to what?” Thankfully, solutions are coming to market to help address these concerns. Also, there is a group working on the standard for the RS listing.

Comments (1)

Brian Cunningham_2's picture

Good article. Hope you're ready for the disCUSSion at the NABCEP Training conference. See you then.

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