An image of a solar PV system appears on the cover of the 2017 National Electrical Code (NEC)—and for good reason.
“The 2017 NEC has more changes than any other version of the NEC since any of us have been alive. Most of those changes are due to what is on the cover of the NEC: a PV system,” says Dr. Sean White, instructor for HeatSpring’s Photovoltaic Systems and the 2017 NEC course, the 40-Hour Advanced Solar PV Installer Training, and others.
“In fact, the very definition of a PV system has changed. Before the 2017 NEC, a PV system included batteries and now it does not,” says White, whose latest book, “Photovoltaic Systems and the National Electric Code” is due out in April. He wrote the book with Bill Brooks, principal, Brooks Engineering, a well-known expert in the solar industry field. White and Brooks often give presentations together about the NEC and other solar issues.
The 2017 code updates include both good news and bad news for installers, their clients, and other industry members, says White, who was the 2014 Interstate Renewable Energy Council Trainer of the Year and is an ISPQ Certified Solar PV Master Trainer.
It’s likely the new requirements will make it more expensive to install PV systems, says White. However, the new regulations will also ensure PV systems are safer. They’ll do a better job of preventing fires, and this protection will prevent insurance rates from increasing for PV system owners.
One of the main changes to the 2017 NEC focuses on rapid shutdown, a term coined by Brooks, says White.
Rapid shutdown requirements were added to the 2014 NEC for PV systems on buildings. Their intent is to make it easier and quicker for first responders to control the PV system circuits associated with a roof-mounted array. The 2017 NEC alters those requirements to boost the safety for first responders by protecting them from PV systems’ energized conductors.
The new code creates a PV array boundary with requirements for circuits inside and outside the boundary, says Michael Johnston, executive director of standards and safety for the National Electrical Contractors Association (NECA).
“Three rapid-shutdown methods are provided for circuits inside the array boundary with an effective date of Jan. 1, 2019,” he says. The rapid shutdown gives first responders a way to reduce the output of PV systems to 30 volts within 30 seconds to ensure safety.
The new code also revised labeling requirements for PV systems to help first responders identify energized PV power circuits, Johnston says.
Companies that sell inverters unable to shut down at the module level aren’t happy about the details and timing of the rapid shutdown requirements in areas that have adopted the 2017 NEC, White notes. “They will require electronics at the module level, which most PV systems in the world do not have.”
However, the new regulations benefit microinverter companies and DC-to-DC converter companies, including Enphase and SolarEdge, whose products can shut down at the module level, White says.
The solar industry is abuzz with talk about these changes, and they even inspired a new name for a rock band, says White. A band called “Rapid Shutdowns” performed at the Intersolar Battle of the Bands, he says.
Other changes to the code are also major, says White. For example, energy storage is no longer considered part of a PV system, which means that energy storage, when paired with PV, is not subject to the 2017 NEC rapid shutdown requirements. All energy storage requirements are no longer part of Article 690, and are instead addressed in Article 706 of the code.
Article 706, a new article, focuses on “energy storage systems,” including capacitors, flywheels, compressed air flow batteries and pre-engineered energy storage systems, among others, says White.
Article 480 also applies to energy storage and has been part of the code for a long time. It focuses on stationary applications of batteries.
In addition, the new code covers large-scale PV electric power production facilities under the new Article 691. While the number of large-scale PV systems is small, they produce more power than the combined output of all residential and commercial PV systems, says Johnston.
The new code allows a PV system with a capacity of 100 kW or larger to have the maximum PV array voltage calculated under the supervision of an electrical engineer, he says.
Systems are considered large-scale PV if they have a capacity of 5,000 kilowatts and are not under exclusive utility control. Only qualified personnel are permitted to maintain and operate these systems, Johnston says.
Also changed in the 2017 NEC are definitions of grounded and ungrounded inverters, says White. He warns that these changes are especially confusing.
“Everything we taught you before the 2017 NEC has changed, or we could even say was wrong!” says White.
What were formerly known as both ungGrounded and grounded inverters are now both called functional grounded inverters. “These functional grounded inverters have the same wiring methods now. If a dc combiner fuse is required, it is only needed on positive or negative, not both. PV wire is no longer required, but you can still use it,” White explains.
But here’s where the new code can really make you perplexed. If you want to use a true ungrounded inverter under the 2017 NEC, you need a transformer.
“If you now want a grounded system, you are probably looking at something very small and definitely not utility interactive,” White says.
While these provisions of the code can be befuddling, White promises that learning about them won’t be so difficult.
When teaching people in the solar industry about the 2017 NEC, White likes to remind students about a quote from Albert Einstein, he says. “Everything should be made as simple as possible, not simpler.”
The 2017 NEC isn’t as complicated as quantum physics, especially when White is teaching it. “I simply get to the point and makes analogies about how things work, analogies that help you remember,” he says.
In addition to his upcoming book about the 2017 NEC, White’s books include “Solar PV Engineering and Installation: Preparation for the NABCEP PV Installation Professional Certification.” He also teaches HeatSpring courses that prepare students for NABCEP exams. They include Solar PV Installer Boot Camp + NABCEP PV Associate Exam Prep and 58-Hour NABCEP Advanced Solar PV Training Series.