Conductors requiring RSD control will be reduced from 10 feet to within 1 foot of the PV array, which will increase the numbers of systems needing RSD. The time frame for voltage to reach less than 30 V will be increased, from 10 seconds to 30 seconds, possibly decreasing the number of inverters that will require additional RSD on their input conductors (due to capacitor discharge time).
The 2017 NEC also will address requirements within the array boundary, offering three options for compliance:
• Option 1: List or field-label the PV array as an RSD PV array.
• Option 2: Limit controlled conductors within the array boundary to 80 V or less within 30 seconds of RSD initiation.
• Option 3: Install nonmetallic PV array with no exposed wiring and the array more than 8 feet from any grounded metal parts.
These new requirements for within the array boundary seem to imply module-level control may play a large role in meeting 2017 requirements, however the new requirements will not be enforced until 2019—giving the industry time to develop the necessary safety and certification standards and various manufacturers time to develop compliant solutions. Revised language will require listing of the RSD equipment as specifically providing RSD protection. Then, off-the-shelf contactors, motorized switches, and shunt trip breakers will only be able to be used if they are listed to a specific RSD UL-standard, which will need to be developed during this time frame.
Finally, section 690.56(C) revises field-labeling requirements for PV systems equipped with RSD, which will help first responders differentiate between systems designed to meet NEC 2014 versus 2017 (i.e. systems that do not control conductors within the array and those that do). In the situation that a building has multiple PV systems built to different NEC standards—such as no rapid shutdown (pre NEC 2014), NEC 2014 compliant, or NEC 2017 compliant. The plaque or directory needs to show a plan view of the building with a dotted line around array areas that remain energized after RSD has been initiated.
Various editions of the NEC are used across the country; not all areas are yet enforcing the 2014 NEC. Several states, including California, are currently operating under the 2011 NEC, and a few states are still enforcing the 2008 NEC. You can search nema.org to find out what NEC cycle is being enforced in each state (or by jurisdiction) and when it was adopted to get an idea of how quickly the next code cycle may be implemented.
In this effort to safely allow firefighters and emergency responders to easily and quickly shut down energized PV system circuits on buildings, the industry as a whole has stepped up with several solutions. With RSD requirements continuing to develop, it is important for system designers and installers to stay on top of the current standards, as well as the upcoming changes and the modern equipment and solutions being offered.