CODE CORNER: Standalone Systems and the NEC

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Major changes occurred in the 2017 National Electrical Code regarding PV system disconnects; where a PV system ends; and what constitutes separate systems, even though they were historically thought of as parts of a PV system (see “Simpler NEC Disconnection Rules” in HP180). Rules that previously resided in Article 690 were relocated within the NEC with the objective of stripping out requirements that were not PV-system-specific. One example is stand-alone systems.

Article 710

While Article 710—“Stand-Alone Systems”—is a new “Special Condition” in Chapter 7 of the NEC, the language is essentially the same as in the 2014 NEC’s Section 690.10. One of the main additions is the scope of Section 710.1, which states that the article covers “power production sources operating in stand-alone mode.” The information is applicable both to complete stand-alone systems as well as to the wiring on the stand-alone side of a multimode inverter, even though the system may normally be operating in parallel with the utility grid.

Also added is the general requirement that all equipment be listed or field-labeled for the intended use. This requirement works in conjunction with 710.15(F), which stipulates that the power supplied by a stand-alone system stays within acceptable voltage and frequency limits of the loads (as a listed product would).

Note there is still a drawing in Figure 690.1(b) showing a stand-alone system; this drawing also includes a PV system (covered by Article 690) and an energy storage system (Article 706). A stand-alone system is defined in Articles 100 and 690 as a “system that supplies power independently of an electrical production and distribution network” (aka independently of the grid or another primary source of power). Expect future editions of the NEC to further segregate different system types so that rules and requirements can be applied only to the relevant equipment and wiring of each.

Section 690.56(A) specifies a labeling requirement for stand-alone PV systems: a directory in a readily visible location on the exterior of the building must state the presence of the system, as well as the location of the system’s disconnecting means. While there is no corresponding requirement in Article 710 (nor are there any rapid shutdown requirements for a stand-alone system without PV), providing this information is valuable to system users and first responders even for stand-alone systems that don’t include PV.

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