A Peek at the 2014 NEC - Part 1

Intermediate
Three-phase string inverter
Three-phase string inverters ranging from 8 kW to 30 kW with a maximum input voltage of 1,000 VDC are becoming common in commercial applications.

The 53rd edition of the National Electrical Code (NEC) is available from the National Fire Protection Association (nfpa.org). It has numerous additions and edits, and some sections have been deleted and some have been reorganized. Technological changes in the industry resulted in particular attention being given to Articles 690 and 705. Plus, there were several Code-wide changes. While adoption dates will vary by state and local authorities having jurisdiction (AHJs), these changes will drive new equipment availability, as well as design and installation best practices. This article provides a broad overview of just some of the changes—other changes will be subjects of future “Code Corners.”

Code-Wide Changes

The definition for “Photovoltaic (PV) System” has been moved out of Article 690 and now resides in Article 100, “Definitions.” Perhaps the move indicates that PV is now fully mainstream, and while the definition hasn’t changed, it still has big implications when it comes to disconnects or conductors sharing a raceway or junction box. 

A more significant Code-wide change is 110.21(B), “Field-Applied Hazard Markings.” PV systems have lots of labeling requirements (see “Code Corner” in HP154), and now the NEC mandates that Code-required labels effectively convey the hazard, be permanently affixed, and be suitable for the environment in which they are installed.  Two Informational Notes reference ANSI Z535.4-2011 standards for guidance on effective words, colors, and symbols to use based on the level of hazard, as well as location requirements and durability standards.  While Informational Notes are recommendations, not enforceable requirements, following the ANSI standards as a best practice will ensure that hazards are clearly identified, ideally with labeling that will last for the system’s life.

Another Code-wide change is the reclassification of high voltage, as defined in Article 490, to “equipment operating at more than 1,000 volts.” This is reflected throughout numerous other Articles, such as 690, Part IX, “Systems over 1,000 Volts.” Section 690.7(C) still limits PV systems for one-and two family dwellings to 600 VDC, and although 1,000 VDC systems were never prohibited on commercial buildings, those applications are now specifically excluded from the category of high-voltage systems, which will make Code-compliant installation more straightforward. Expect to see more 1,000 VDC systems in commercial applications as equipment manufacturers introduce more modules, inverters, and balance-of-system (BOS) components rated for this voltage. Note that workspace clearances have not changed and are still different for systems greater than 600 V [Table 110.34(A)] and systems less than or equal to 600 V [Table 110.26(A)(1)].

Article 690: Solar Photovoltaic (PV) Systems

In many cases, throughout Article 690, “photovoltaic” has been abbreviated to “PV,” which helps to shorten the text. New definitions include:

DC-to-DC Converter: A device on a DC PV circuit that can manipulate voltage and current, such as products from SolarEdge, Tigo, and others.

Direct-Current (DC) Combiner: The Code says that basically any devices where two or more DC inputs are paralleled to form one DC output fall into this category (including combiner boxes, and sub- or recombiners).

Multimode Inverter: An inverter that can operate in both utility-interactive and stand-alone modes, such as in grid-tied with battery backup systems or SMA America’s Secure Power Supply inverters.

Section 690.4 was broadly titled “Installation,” and now is more appropriately named “General Requirements.” Specific sections that dealt with installation, such as “Identification and Grouping” and “Module Connection Arrangement” have been moved to “Part IV: Wiring Methods.” Others, such as “Circuit Routing,” have been moved and modified—changed to 690.31(G)(1), “Embedded in Building Surfaces,” which no longer addresses routing inside of a building.

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