Understanding Rapid Shutdown Requirements for Your DIY Solar Project
What Is Solar Rapid Shutdown?
If you are installing your own solar system, it must meet rapid shutdown requirements. Solar rapid shutdown enables rooftop solar panel systems to de-energize quickly in case of emergency.
The National Electrical Code (NEC) set this critical safety measure and has been updated since its inception in 2014. The National Fire Protection Association (NFPA) wrote rapid shutdown functionality requirements into the NEC to keep first responders safe from exposure to live electricity sources.
The NEC receives updates every three years from the NFPA. While it’s in effect nationwide, state and local governments dictate and enforce different code versions. Be sure you understand which ones apply to your solar system.
Dangers of Live Solar PV Systems
A PV (photovoltaic) system’s DC conductors are usually live any time the sun is out. Without a rapid shutdown system, there is no safe way to turn off your system’s DC wiring on your roof, in the attic or running down the side of your house. If you have called firefighters to respond to a fire at your home, there usually isn’t time to figure out how to deal with live solar conductors. Consequently, the NFPA established guidelines for rapid shutdowns to keep first responders -- and homeowners -- safe.
Differences Between NEC 2014 and NEC 2017
Exactly where and how you must control your PV conductors changed between NEC 2014 and NEC 2017. Understand which code version your city or county follows to ensure you comply.
- NEC 2014: Makes no mention of the location of the device that starts the rapid shutdown process.
- NEC 2017: Clarifies that the device that starts the rapid shutdown process must be in a readily accessible location outside the building.
Distance From The Solar Array
- NEC 2014: PV conductors inside a building, more than 10 feet from the array or more than 5 feet long, must be shut down to 30 volts or less within 10 seconds of rapid shutdown initiation.
- NEC 2017: PV conductors inside a building, more than 1 foot from the array or more than 3 feet long, must be brought down to 30 volts within 30 seconds. Conductors within the array must be brought down to 80 volts within 30 seconds.
How Do You Meet Rapid Shutdown Requirements?
The easiest way to meet rapid shutdown requirements is to install a system that is already listed or field labeled with rapid shutdown capabilities. The SolarEdge system incorporates DC optimizers at every solar panel, while Enphase incorporates microinverters installed at every panel.
These devices shut off the power around and within the solar array at the flip of a switch. Adhere to the appropriate rapid shutdown labeling from your solar kit distributor and you’re good to go!
If you want to install a more traditional central inverter, you still have options. For NEC 2014 compliance, include a rapid shutdown device on the roof at the edge of the PV array and link it to the switch at ground level.
To meet NEC 2017 requirements, install module-level equipment to manage the rapid shutdown at each solar panel. Order the correct equipment and install it at the same time as the solar panels.
If you’re reading this before installing your solar panel system, great! You’re well prepared to install your system within the NEC compliance guidelines for your area. If you’ve already done your array without rapid shutdown, it’s not an easy fix, unfortunately.
If you need help getting into compliance with NEC guidelines, contact us today.