Chapter 3--Wiring Methods
Chapter 3 has many significant changes. 300.4(E) has been revised to clarify the requirements for wiring near roof decks which were added in the 2008 NEC®, and a new subsection, 300.4(H), was added to address structural expansion and deflection joints.
300.11(A)(2) has been revised to require all suspended ceiling wires supporting electrical equipment to marked and distinguishable from the other ceiling wires. This provision previously only applied when the ceiling was fire-resistance rated.
300.22 has been extensively revised to provide consistency with the terms used in widely adopted mechanical codes, such as the International Mechanical Code.
Article 310 has been extensively revised. The experienced Code user will recognize a complete renumbering of not only the sections, but the tables as well. The ampacity adjustment provisions have been clarified, the correction factors for raceways on rooftops have been made more stringent, and the ampacities of some conductors have been reduced!
Changes to 312.8 now require a warning label on some cabinets, and the requirements for the weight ratings of boxes in 314.27 have been revised.
Changes to Article 334, Type NM Cable, clarify the permitted uses of Type NM Cable in dwelling unit accessory buildings, and the ampacity adjustment requirements of 334.80 have been clarified.
The controversial issue of unsupported raceways (added in the 2008 NEC) has been removed altogether, resulting in a different controversy now. Support requirements for Flexible Metal Conduit and Liquidtight Flexible Metal Conduit have been changed as well.
Article 392 experienced a much needed face-lift this Code cycle. Changes to this article include a uses permitted and uses not permitted section, similar to the 3xx.10 and 3xx.12 sections found in other Articles of Chapter 3. The provisions for the grounding and bonding of cable tray systems have also been made clearer in 2011.
Chapter 4--Equipment for General Use
Significant changes to Chapter 4 can be found throughout the chapter, beginning in Article 404, Switches. 404.2(C) contains a very substantial change--one that has many electricians grumbling. With this changes, the days of two conductor switch loops and dead-end three way switches are in the past, except for raceway systems and some unfinished areas of buildings. This new requirement will mandate a grounded conductor at each switch location for line-to-neutral switch controlled loads.
Another change in this article, this time to 404.9, will have some installers and many inspectors smiling. An allowance for certain switches to be installed without the benefit of an equipment grounding conductor has been made. These switch assemblies contain no metal parts, and can only be connected to nonmetallic cover plates, so safety is not compromised. Previously the AHJ was forced to use 90.4 and waive the requirement if this product was to be installed.
As wiring systems become older, the Code has added provisions for updating systems, and this edition of the Code is no different. Replacement of AFCI protected circuits, tamper-resistant receptacles, and weather-resistant receptacles are all now addressed in the Code, and tamper-resistant receptacles are now required in guest rooms, guest suites, and child care facilities.
Many revisions throughout Article 410 have been to address LED luminaires and their drivers.
Perhaps the most controversial change in this edition can be found in Article 445, which covers generators. 445.20 now requires that all 125V receptacles that are part of a generator, 15 kW or smaller, must have GFCI protection.
Last but certainly not least in Chapter 4, a new section 450.14 has been added, which requires a disconnecting means for transformers (other than Class 2 and Class 3 transformers). Although commonly thought to already be a requirement, it has never been found in the Code until now, and will require substantial consideration in the design of an electrical system.
Chapter 5--Special Occupancies
Listing requirements for different types of equipment in hazardous (classified) locations have been added for Class I, Class II, and Class III locations.
Clarifications to the disconnect requirements for fuel dispensers can be found in 514.11 and 514.13, and the "redundant" equipment grounding provisions in 517.13 have also been clarified.
Installers, and particularly designers, might be shocked to find that 517.16 now prohibits isolated ground receptacles from being used in patient care areas.
The GFCI requirements for assembly occupancies (Article 518) and carnivals, circuses, fairs, and similar events have been clarified. And a new requirement for GFPE protection at marinas and boatyards should result in a much safer environment in these areas.
Chapter 6--Special Equipment
Article 645, covering information technology equipment and rooms, has been revised with new definitions, revised requirements, and new provisions.
Article 680 has been changed to incorporate a new concept, that of the "low voltage contact limit." Perhaps most substantially in Article 680, the rules on equipotential bonding have been revised…again, and the bonding of hydromassage bathtubs has been expanded to provide for replacement motors.
Because solar photovoltaic systems are such an expanding technology, it should come as no surprise that the article experienced an incredible amount of changes. One need only glance at the Code book to recognize this fact. Of particular interest to those involved in these systems, 690.47(D) has been deleted, removing the requirement for an additional grounding electrode for a ground or pole mounted PV array.
As mentioned earlier, a new Article 694 covering small wind systems has been added, and there are some change in Article 695 for fire pumps, mostly having to do with the routing of fire pump circuitry.
Chapter 7--Special Conditions
Articles 701 and 702 have been reorganized in an effort to harmonize the numbering system for emergency systems, legally required standby systems, and optional standby systems. Article 725 and 760 saw little action in this Code revision cycle. 725.3 and 760.3 saw most of the changes, which inform the Code user about which Article 300 provisions apply to these installations.
As is often the case, Article 770, covering optical fiber cables, saw extensive revisions, but most of them were editorial in nature. New to the 2011 NEC is the concept of "cable routing assemblies", a wiring trough for limited energy circuits. The definition for this system can be found in 770.2
Chapter 8--Communications Systems
Like the past few Code cycles, Chapter 8 saw a lot of revisions in 2011, most of which were editorial in nature. With the removal of the term "grounding conductor" from the Code, many changes to the text were made. Removal of the requirement of insulated grounding electrode conductors makes for consistency throughout the Chapter 8 articles, and new tables added to these articles should make for easier navigation through these articles.
As discussed earlier in this book, a new Article 840 has been added, which covers premises-powered broadband communications systems.
A new Table 10 has been added, which addresses finely stranded conductor. Most of the information in this table is borrowed from UL 486A-B, Table 14.
Annexes A through I
A new Annex, Annex I, has been added to provide tightening torques for terminations. This new annex consists of two tables, each of which is borrowed from UL 486A-B.