Key changes in the 2011 NEC
The most recent National Electrical Code (NEC) edition has some important changes.
Kenneth L. Lovorn, PE, Lovorn Engineering Assocs., Pittsburgh
With rare exception, the National Electrical Code (NEC) changes every three years. While many of these changes can be considered nominal rewording that just clarifies the intent of a particular code article, there are always some changes that have a major impact on the code’s scope. The most recent NEC is the 2011 edition, and the following are some of the more important changes that were implemented during this cycle.
110.24 Electrical service equipment must now be field-labeled with the maximum available fault current at the incoming terminals of the equipment and the date that the fault current calculation was made. The impact of this requirement is that when modifications are made to the electrical service (even by the serving utility), the available fault current must be recalculated. By the serving utility increasing the service transformer or replacing the transformer with one of lower impedance, the service equipment may be required to be replaced to withstand the new available fault duty.
110.3(A)(1) This article always required that equipment must be installed in accordance with the listing and labeling requirements. However, it now states that any special conditions that may be essential to the safe use or functioning of the equipment could be included as a part of the listing and labeling. This will reinforce the use of fuses for the installation if the equipment was tested by UL with fuses.
200.4 In the past, it was common to share neutral conductors for three single-phase circuits in a 3-phase, four-wire home run. With the new rule in 200.4, neutral conductors shall not be shared unless they are specifically permitted to be shared, as indicated elsewhere in the code. Due to the widespread occurrence of harmonic currents generated by switching power supplies, overloaded neutral conductors have become more of a problem. By requiring dedicated neutral conductors, this overload problem can be eliminated. (See Figure 1.)
210.8 Receptacle outlets have always been located based on code spacing and the environment, without any consideration as to what might be located in front of them. Now, ground-fault circuit interruption (GFCI) receptacles are required to be installed in a readily accessible location. This means that it is a code violation to locate a piece of furniture in front of a GFCI outlet. Either the outlet must be moved or the furniture must be relocated. We are certain that this will be very difficult to enforce, just like the rules against using dedicated electrical closets for material storage.
210.8(B)(5) Exception No. 2 Many engineers have assumed for years that any receptacle located near a sink should be a GFCI type. However, the code required GFCI receptacles in mostly residential and kitchen applications. Now this rule has been expanded and includes sinks in healthcare facilities. The details of this change should be carefully reviewed because there are some areas within a healthcare facility in which GFCI receptacles are not required because their use would create a greater hazard from the possible nuisance outages.
210.12(A) Types MC (metal clad) and AC (armor clad) cable may now be used between the panel and the first device, when arc-fault circuit interrupter (AFCI) protection is required for that circuit. The code panel felt that both conductor types would provide adequate physical protection for the home run, so that the first device could be a feed-through type AFCI, rather than having an AFCI branch circuit breaker.
210.12(B) When modifications or extensions are made to an existing branch circuit in a residence and the code requires that the area have AFCI protective devices, the modified or extended branch circuit must now have an AFCI device installed. This new AFCI device must be placed in the circuit, within the panel or at the first outlet.
230.44 If cable trays contain service entrance conductors (types SE (service entrance), MC, MI (mineral insulated), and IGS (integrated gas spacer)), then the trays must be labeled as such. The signage shall be located so that the service conductors may be readily traced through their entire length. (See Figure 2.)
250.92(B) Bonding conductors are required around reducing washers and concentric knock-outs for all service entrance conduit connections at the service entrance equipment. While concentric knock-outs are generally sturdy enough, the lack of adequate material to carry the possible short-circuit ground currents is of concern. By requiring bonding conductors around these areas, the ground current will have an adequate, low-impedance path to assist in tripping overcurrent devices during a fault condition.
300.4(E) Cables, conduits, boxes, and other raceways are not permitted to be installed closer than 1½ in. to the roof deck. This is intended to prevent damage to the electrical components by the typical roofing fasteners.
300.5(C) Type MI and MC cables that are listed for direct burial or in concrete are permitted to be installed in fill or within the concrete, below buildings. This is an exception to the requirement that all raceways below a building must be within a raceway.
300.11(A)(2) When independent electrical equipment support wires are installed within dropped-ceiling areas, they shall be distinguished by color, tagging, or other permanent effective means. (Note: While the code does not say “permanent,” it is very applicable to this change because the explanation says that identification is intended for identification in the future. Thus if the “effective means” is not permanent, then it cannot be used in the future.) This will assist both installers and inspectors in determining which suspension wires are intended to support electrical and which are intended to support other systems or the ceiling systems. (See Figure 3.)
300.50(B) While it would appear obvious, the NEC has now determined that the interior of underground raceways shall be considered to be wet locations. Therefore, all underground conductors and splices must be listed as suitable for wet locations.
310.10(H)(1) Conductors smaller than 1/0 are no longer permitted to be paralleled for increased ampacity. When conductors are paralleled, the rules are now much more restrictive because each conductor must be: the same length, same conductor material, same circular mil area, same insulation type, and terminated in the same manner. This change is attempting to assure that each of the paralleled conductors will carry its share of the total load. Any variance in the aforementioned parameters could modify the individual conductor impedance, which would result in unequal load sharing. This could, potentially, overload one of the conductors and cause it to fail.
Table 310.15(B)(2)(a) The temperature correction factors that were previously located as small print—below the conductor ampacity Table 310.16—have now been relocated to their own table. These factors were sometimes ignored by the industry, as was the note at the top of Table 310.16 that stated that the ampacities were at a 30 C ambient. Because many electrical spaces were designed to operate at 40 C ambient, the conductors would operate at temperatures greater than their rating. Now that the temperature correction factors have their own table, it should be clearer that these factors must be applied to all conductors that are operating in ambient conditions that exceed 30 C. In addition, most of 310.16 has been renumbered, changing Table 310.16 to Table 310.15(B)(16).
310.15(B)(3)(c) Raceways that are circular in cross-section (e.g., conduits) shall have temperature adjustment factors that are shown in Table 310.15(B)(3)(c) applied to their ampacities. These adjustment factors shall be applied in addition to the outdoor ambient temperature compensation factors.
348.42 angle connectors for flexible metal conduit (FMC) are not permitted to be used in locations where the connector is concealed. In the prior code, the phrase used was, “Angle connectors shall not be used for concealed raceway installations.” It was not clear that only the angle connector was not permitted to be in a concealed location, not all FMC installations.
392.18(H) Cable trays are now required to be marked “Danger--High Voltage--Keep Away” when the cable trays contain conductors rated above 600 V. These labels are similar to those required for cable trays containing service entrance conductors. (See Figure 4.)
406.4(D)(4) The language requiring that AFCI devices be installed when receptacles are being replaced, as noted in 210.12, is also included here.
406.4(D)(5) For installations in which tamper-proof receptacles are required and receptacles are being replaced, the installer is now required to install tamper-proof receptacles. In the past if there were major renovations, the current provisions of the code would kick in and the entire residence would have to be brought up to code, while minor renovations would typically permit the installation to be grandfathered. This is another effort to improve the safety of existing residential installations when grandfathering normally would have not required these areas to be modified.
406.13 Tamper-resistant receptacles are now required in all guest rooms and guest suites. This gives guest rooms the same level of safety for small children as residences.
406.13 Tamper-resistant receptacles are now required in all day-care facilities. Because small children are normally in day-care facilities, it only follows that those areas should be as safe as residences. Best practice indicates that an engineer should responsibly design a day-care center with tamper-resistant receptacles, even if this isn’t a code requirement.
410.16 Luminaires in clothes closets are now permitted to be either surface or recessed LED, fluorescent, or totally enclosed incandescent fixtures. It should be noted that the International Energy Conservation Code (IECC) limits the lighting power density to 1 W/sq ft or less in hotels, multifamily dwellings, and dorms. In addition, at least 50% of the permanently installed fixtures in single-family residential units must be of the high-efficiency type. While the NEC permits totally enclosed incandescent fixtures, they can be used very infrequently in single-family residences due to the IECC requirements and cannot be used at all in hotels or other multiple occupancy buildings due to the maximum lighting power density requirements.
410.130(G)(1) During the 2008 code cycle, each discharge light fixture was required to have an individual disconnecting means. This requirement has been modified to require that a disconnecting means be installed for existing fixtures not having disconnecting means, within sight of the fixture or within the light fixture itself when the ballast is replaced.
450.14 Transformers are now required to have line-side disconnecting means within sight of the transformer, or the disconnecting means must be lockable. This brings transformers into line with other electrical elements, such as motors, generators, and appliances.
500.2 A definition has been added for combustible dusts. There has been some confusion as to whether a dust was combustible or hazardous, so this definition is an attempt to define whether a dust is potentially combustible or whether it is just a nuisance.
501(B)(5) This new code paragraph clarifies the differences between Class 1, Division 1, and Division 2 installations for flexible conductors. In the past, the method of installation of flexible conductors was not clear in the two locations and these new rules should clarify the differences.
517.13(B) The requirement for redundant grounding conductors has been clarified and states that there must be an insulated bonding jumper from the metallic box to the equipment grounding conductor. The grounding/mounting screws are considered to be the redundant ground, and using only these screws does not meet this requirement.
517.16 In keeping with the previous redundant grounding requirement, isolated ground receptacles are not permitted to be installed within patient care areas.
517.17(B) If there is only one level of overcurrent protection between the incoming service entrance and transfer switches, the second level of ground fault protection that is normally required for healthcare facilities shall not be installed downstream of the transfer switches. This is consistent with the requirement that ground fault protection not be installed in the emergency power generating equipment distribution system. (See Figure 5.)
517.18(A) Receptacles in patient bed locations shall not be a part of a multiwire branch circuit (i.e., have a neutral in common with another phase conductor).
517.160(A)(5) Conductors for an isolated power system shall be identified by a continuous, distinctive colored stripe other than white, green, or gray along their entire length.
547.5(G) For engineers designing barns, the code no longer permits deleting GFCI protection on an outlet for a piece of dedicated equipment when that piece of equipment is within 3 ft of another GFCI outlet. This omission lasted for only a single code cycle; it was instituted in 2008 and deleted in 2011.
620.53 Exception disconnects are required for elevator cab lights and ventilation, but if the ventilation motor is less than 2 hp, a general-use snap switch may be used as this disconnecting means. The switch must still be able to be locked in the open position, but a nonfused safety switch or individually mounted breaker is no longer required.
645.17 Power distribution units (PDUs) in IT spaces were previously allowed to have multiple panelboards within a cabinet only if those panelboards were limited to 42 pole spaces. That restriction has now been lifted, making the requirements for PDU panelboards consistent with the requirements for other panelboards (restrictions limiting other branch-circuit panelboards to 42 poles were eliminated in the 2008 NEC revision cycle).
690 Due to the wide popularity of photovoltaic (PV) systems, broad changes have been made to article 690 that are too extensive to include here. For those engineers involved in the design and installation of PV systems, these new code requirements should be carefully reviewed.
694 A new article to address wind-powered electric generating systems has been added to the 2011 NEC. Like other renewable power sources, the increased popularity of these systems has required that a standard for design, installation, and inspection be established to maintain safe installations.
695 The code for electrically driven fire pumps has been modified to correlate to the requirements of NFPA 20. These changes are extensive and should be carefully reviewed when designing or installing fire pump installations.
700.10(D)(1) Feeder circuit cables for emergency systems must now be rated for a minimum of 2 hours. This will provide an additional margin of safety for occupant movement to a safe location, in case of a fire.
700.27 Exception Selective coordination is no longer required for overcurrent devices that are installed in series. Therefore, it is now legal for a distribution breaker to feed a downstream panelboard that has a main circuit breaker. This will make maintenance much easier and safer than previously possible because personnel can now have a local disconnect at the panel, without having to go back to the feeding breaker and lock it out for maintenance operations.
701.6(D) While ground fault protection is still not permitted on emergency distribution systems, and is still not required for legally required standby systems, there is now a requirement for ground fault indication for legally required standby systems similar to that previously required only for emergency systems. Therefore, maintenance personnel can be notified, both audibly and visually, that there is a ground fault on the emergency system, but this will not interrupt the operation of the system.
Lovorn is president of Lovorn Engineering Assocs. He is a member of the Consulting-Specifying Engineer editorial advisory board.
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