Bigger than ever: the 2005 National Electrical Code

This 772-page document summarizes a century of electrical industry progress

EXERCISING LEGAL AUTHORITY OVER ELECtrical installations throughout most of the U.S., NFPA 70-the National Electrical Code-has now been republished in its 2005 edition, following the customary three-year revision cycle, by the National Fire Protection Association of Quincy, Mass.

The document's steady growth continues-from 644 pages in 1999 and 711 pages in 2002, the NEC has expanded to 772 pages for 2005. One reason, of course, is growth in technology. For example, the advent of photovoltaics, fuel cells, fiber optics, and arc fault protection has required repeated addition of new Code Articles. Yet the earliest electrical art has remained in place. Article 394 continues to govern installation of "knob-and-tube" wiring-a century-old practice.

Adding to Code content in the 2005 edition are four new Articles. Taking them in order:

A relatively new product that, according to the manufacturer's representative who proposed this addition to the Code, had been "restricted in its uses," high-density polyethylene (HDPE) conduit is now covered by a new Article 353. The text governs HDPE use in non-exposed, non-hazardous locations, outside buildings, and with certain size and temperature limitations. Details of bends, joints, and ground conductor usage are also spelled out.

Despite initial rejection for lack of a two-thirds vote (there were many objections), a new Article 409 eventually made its way into the 2005 Code. Titled "Industrial Control Panels," it defines such apparatus as "An assembly of a systematic and standard arrangement of . . . components such as motor controllers, overload relays, fused disconnect switches, and circuit breakers [with such related devices as] pushbutton stations, selector switches, timers . . . with associated terminal blocks, pilot lights, and similar components."

That describes most line-ups of motor control centers (MCC's). What the Code Panel apparently had in mind, however, was "field manufactured" panels designed to control lighting, conveyor, and air conditioning systems. Features dealt with in the text (mostly by reference to other Articles) include busbars and connections, wire space, markings, grounding, and overcurrent protection. The proposal argued that rules for such installations were "long overdue" because of "a significant increase in the use" of control panels, and that "many misapplications" of control products had resulted from the absence of such rules. Opponents claimed that such problems weren't identified, and that parts of the proposed Article duplicated material elsewhere in the Code.

Following lengthy controversy, the European concept of Zones 0, 1, and 2 was adopted in the 1996 NEC as an alternative method of defining Class I areas involving flammable liquids, gases, and vapors. A new Article 506 now extends that concept to Classes II and III (combustible dusts, fibers, and flyings) by creating Zones 20, 21, and 22. Equipment features suited to such areas include "dust-ignitionproof," "dusttight," and "pressurized."

A fourth new Article 682 provides for "Natural and Artificially Made Bodies of Water." Article 680 continues to govern electrical installations involving swimming pools and "similar" facilities. However, that wasn't considered applicable to "storm retention basins, sewage treatment ponds, fish farms, and irrigation channels." Water levels there may change frequently. Various floating structures may be present.

Most provisions of Article 682 concern ground fault protection, electrical services, and disconnecting means. Written by a Task Group within Code Panel 17, following various proposals dating back to 1996, the Article requires determination of an "electrical datum plane" based on the highest expected water level. Electrical connections below that plane must be suitable for submergence. When water level rises to that plane, "service equipment must disconnect."

Semantic hairsplitting

Space does not permit detailed review of the many changes to existing NEC articles, most of them involving minor style or editorial revision. As an example of the type of semantic hairsplitting common during each Code cycle, consider Section 547.6, dealing with "agricultural buildings." One passage was worded this way in the 2002 Code:

"The disconnecting means shall not be required to contain overload protection."

In the 2005 edition, the same provision now reads:

"The disconnecting means shall not be required to provide overcurrent protection." Is there really a difference?

A further illustration involves the term used to describe how certain numbers should be derived. In Section 430(D), for example, the Code explains how to size conductors feeding multiple loads, saying that "the conductor ampacity shall be computed" in a certain way. Similar wording has appeared in many places throughout the Code. For the 2005 edition, the NEC's Technical Correlating Committee (following the lead of a Usability Task Group) replaced the word "computed" with "calculated" throughout the document. The reason? "Calculate" was already the basic word in many places including titles.