It’s that time again—a new edition of the National Electrical Code (NEC) has been published. Early-adoption states are already beginning to enforce it, and folks in the industry—ranging from installers to designers to manufacturers—are studying it. And in case you haven’t noticed, a PV array made the cover—a clear indication of both the rapid growth in deployment of PV systems, as well as the significant changes in regard to PV systems that have occurred in the NEC.
Section 690.10 now refers to the new Article 710, “Stand-Alone Systems.” While the majority of requirements in Article 710 are the same as they were in Section 690.10 in 2014, the article’s scope applies to sources “operating in stand-alone mode,” thus covering multimode systems (which can be both grid-tied and stand-alone, and to which Article 690 also applies). Load-side wiring of stand-alone systems is covered in 710 as well as many other articles in chapters 1 through 4 of the NEC. Since stand-alone systems may or may not incorporate a PV system, it made sense to move them from PV-specific Article 690.
New Article 691 applies to “Large-Scale Photovoltaic (PV) Electric Power Production” facilities—specifically those with a generating capacity of at least 5 megawatts AC. Generating capacity is a newly defined term—it is the sum of the rated continuous power output of all parallel-connected inverters at 40°C (104°F). The popularity of large-scale PV systems is rapidly growing. Since these systems are “operated for the sole purpose of providing electric supply to a system operated by a regulated utility” and only accessible by qualified personnel, large-scale PV systems now have exemptions from a few requirements in Article 690, as well as the opportunity for engineered designs that may result in methods and materials not permitted under other sections of the NEC.
The introduction of Article 706, “Energy Storage Systems (ESS),” reflects NEC efforts to keep up with industry developments. Article 706 focuses on systems—both AC and DC—including unconventional storage technologies (such as flow batteries, capacitors, and flywheels) and associated equipment. Three types of ESS are defined: “self-contained” (assembled, packaged, and installed in a single unit or container, and usually “manufactured by a single entity”); “pre-engineered of matched components” (field-installed, consisting of separate components supplied as a system); and “other.” ESS of up to 100 V are allowed in dwelling units; if there are no live parts accessible during routine maintenance, the voltage can be higher (with no stated limit). Products already on the market that exceed 100 volts and that are intended for use in residential applications will fall under this allowance.
Also new in the 2017 NEC is Article 712, “Direct Current Microgrids.”