In keeping with our tradition of translating the NEC's changes every three years and keeping you informed of revisions that will affect you, EC&M presents the final installment in its 2002 NEC analysis. This month, we cover revisions to Chapters 6-9. (NOTE: As you make your way through each change, keep in mind that paraphrased excerpts from the NEC are shown as indented text, with new material and changes underlined. An explanation for the revision follows each discussion.)
600.21 Ballasts, Transformers, and Electronic Power Supplies
(F) Suspended Ceilings. You may install ballasts, transformers, and electronic power supplies above suspended ceilings, provided their enclosures are securely fastened in place and not dependent on the suspended ceiling grid for support. Ballasts, transformers, and electronic power supplies installed in suspended ceilings cannot be connected to the branch circuit by flexible cord.
Intent: This change correlates with 400.8(2) and (5), which prohibit flexible cords within the space above a suspended ceiling.
645.5 Supply Circuits and Interconnecting Cables
(2) Branch Circuit Supply Conductors. You must install the branch-circuit supply conductors to receptacles or field-wired equipment within a raised floor in rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, electrical metallic tubing, electrical nonmetallic tubing, metal wireway, nonmetallic wireway, surface metal raceway with metal cover, nonmetallic surface raceway, flexible metal conduit, liquidtight flexible metal conduit, or liquidtight flexible nonmetallic conduit, Type MI cable, Type MC cable, or Type AC cable.
Intent: The new text clarifies you can install metal or nonmetallic raceways of all types within the raised floor area in an information technology (IT) equipment room because this area is not subject to physical damage and it is not considered a plenum space [300.22(D)]. You can install control, signal, and communications cables such as CL2, CM, MP, or CATV within the raised floor area in an IT equipment room [645.5(D)(5)(c)].
An Article covering the wiring requirements for “Technical Power” or “Balanced Power Systems” was added to the 2002 NEC. Technical power is a separately derived, 120V line-to-line, single-phase, 3-wire system with 60V to ground from each ungrounded conductor. Technical power systems reduce objectionable noise in sensitive electronic equipment locations. They are restricted to commercial and industrial occupancies under close supervision by qualified personnel [647.3]. You cannot install them in dwelling units.
Intent: Technical power has been permitted in the NEC since 1996. However, it was located in Art. 530 — Motion Picture and Television Studios and Similar Locations, so its use was limited to these applications. By locating the requirements in a separate Article, its use can be greatly expanded.
Art. 680 was reorganized, and many of the rules were relocated within the article. These changes comply with the new style and format of the Code and make the Article easier to use.
(B) Communications Systems. Communications cables such as telephone, radio, and CATV cables within the scope of Arts. 800 through 820 must be located no less than 10 ft from the water's edge of swimming and wading pools, diving structures, observation stands, towers, or platforms.
Intent: This new subsection was added to establish the minimum overhead clearance from swimming pools and other structures for communications cables within the scope of Arts. 800 through 820.
(C) Network-Powered Broadband Communications Systems. Overhead network-powered broadband communications systems conductors must be located no less than 22.5 ft from the water's edge of swimming and wading pools or the base of diving structures, and there must be not less than 14.5 ft clearance in any direction from the observation stands, towers, or diving platforms.
Intent: This subsection establishes minimum overhead clearance for network broadband communications cables [Art. 830].
The word “maintenance” was added to the heading. The section's revised text reads:
One or more means to disconnect all ungrounded (hot) conductors must be provided for all utilization equipment other than lighting. Each means must be accessible and within sight of its equipment.
Intent: This change clarifies the maintenance disconnecting means does not apply to lighting equipment. All disconnecting means are switches [Art. 404], and switches must be located at least 5 ft horizontally from the inside walls of a pool unless separated from the pool by a solid fence, wall, or other permanent barrier [680.22(C)].
(4) Restricted Space. You can install one 15A or 20A, single-phase, 125V receptacle not less than 5 ft measured horizontally from the inside wall of the pool at a dwelling unit if the dimensions of the lot do not allow the receptacle outlet required in 680.22(A)(3) to be 10 ft from the water.
Intent: This new rule allows the required 15A or 20A, single-phase, 125V receptacle for outdoor pools and spas for dwelling units [680.22(A)(3)] to be located less than 10 ft, but not closer than 5 ft, from the pool, if the dimensions of the property prevent locating the receptacle 10 ft away as required in 680.22(A)(3).
(5) GFCI Protection. All 125V receptacles located within 20 ft of the inside walls of a pool or fountain must be protected by a ground-fault circuit interrupter. Receptacles supplying pool pump motors rated 15A or 20A, single-phase, 120V through 240V must be provided with GFCI protection.
Intent: The revised text clarifies GFCI protection is required for all 15A or 20A, 120V through 240V circuits that supply single-phase receptacles for pool pump motors.
(1) Metallic Parts of Pool Structure. You must bond all metallic parts of the water structure, including the reinforcing metal of the pool shell, coping stones, and deck to a common bonding grid [680.26(C)]. Steel tie-wires are suitable for bonding together reinforcing steel. Where the reinforcing steel is encapsulated with a nonconductive compound, you must make provisions for an alternate means to eliminate voltage gradients, which would otherwise be provided by unencapsulated, bonded reinforcing steel.
Intent: The revised text requires you to bond all reinforcing steel of the water structure to a common bonding grid, and any reinforcing steel that is encapsulated with a nonconductive compound must be provided with an alternate means to eliminate voltage gradients.
There is no acceptable method for bonding nonconductive-coated steel, so a task group has been assembled to investigate this issue and provide data to the industry on how this could be accomplished. Now, you can only use steel without a nonconductive coating for swimming pools, outdoor spas, and hot tubs because there is no way to use structural steel with nonconductive, anti-corrosion coating to eliminate voltage gradients.
(C) Requirements for Disconnecting Means. You must provide a means to disconnect all conductors in a building or other structure from the photovoltaic system conductors in accordance with the following:
Location. You must install the photovoltaic disconnecting means at a readily accessible location inside or outside of a building or structure nearest the point of entrance of the system conductors. You cannot install the disconnecting means in bathrooms.
Marking. You must permanently mark each photovoltaic system disconnecting means to identify it as a photovoltaic system disconnect.
Suitable for Use. Each photovoltaic system disconnecting means must be suitable for the prevailing conditions. Equipment installed in hazardous (classified) locations must comply with the requirements of Arts. 500 through 517.
Maximum Number of Disconnects. The photovoltaic system disconnecting means must consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard.
Intent: This new subsection clarifies the disconnecting means for the PV system must comply with similar requirements in Art. 230 for services.
A section was added to Art. 690 to cover the identification requirements for photovoltaic power systems supplying buildings, structures, or both:
(A) Facilities with Standalone Systems. Any building, facility, or structure with a photovoltaic power system that is not connected to a utility service source and is a standalone system must have a permanent plaque or directory installed on the exterior of the building or structure at a readily visible location acceptable to the Authority Having Jurisdiction (AHJ). The plaque or directory must provide the location of system disconnecting means and information regarding whether the structure contains a standalone electrical power system.
(B) Facilities with Utility Services and PV Systems. Buildings, facilities, or structures with both utility service and a photovoltaic system must have a permanent plaque or directory providing the location of the service disconnecting means and the photovoltaic system disconnecting means if they are not located at the same location.
Intent: The required plaque or label enables personnel to quickly locate the disconnecting means to facilitate and speed the shutdown of all power to a building in an emergency.
This Article identifies the requirements for the installation of fuel-cell power systems, which may be standalone or interactive with other electrical power production sources and may be with or without electrical energy storage, such as batteries.
Fuel Cell. An electrochemical system that consumes fuel to produce an electrical current. The main chemical reaction used in a fuel cell for producing electrical power is not combustion. There may, however, be sources of combustion used within the overall fuel cell system such as reformers/fuel processors.
Fuel Cell System. The complete aggregate of equipment used to convert chemical fuel into usable electricity. A fuel cell system typically consists of a reformer, stack, power inverter, and auxiliary equipment.
The fuel-cell system must be evaluated and listed for its intended application prior to installation.
Intent: Because of the complexity of a fuel cell system, the NFPA decided it was best to require these systems to be listed as a complete assembly.
(6) Disconnect. Where an outdoor-housed generator for emergency circuits is equipped with a readily accessible disconnecting means located within sight of the building or structure supplied, an additional disconnecting means is not required on or at the building or structure for the generator feeder conductors.
Intent: The new wording clarifies a disconnect for the feeder from the generator is not required at or on the building or structure, if the emergency generator disconnecting means is within sight of the building or structure.
(5) Disconnect. Where an outdoor-housed generator for legally required circuits is equipped with a readily accessible disconnecting means located within sight of the building or structure supplied, you don't need an additional disconnecting means on or at the building or structure for the generator feeder conductors.
Intent: The wording in this new subsection clarifies that a disconnect for the feeder from the generator is not required at or on the building/structure, if the emergency generator disconnecting means is within sight of the building or structure.
(E) Connection Ahead of Service Disconnecting Means. Where acceptable to the AHJ, the Code permits connections located ahead and not within the same cabinet, enclosure, or vertical switchboard section as the service disconnecting means. The legally required standby service disconnect must be sufficiently separated from the normal service disconnection means to prevent simultaneous interruption of supply through an occurrence with the building or groups of buildings served.
Intent: The new wording clarifies the NEC permits connections ahead of and not within the same cabinet, enclosure, or vertical switchboard section as the service disconnecting means to supply standby power, where acceptable to the AHJ.
The systems covered by this Article consist of those that are permanently installed, including prime movers, and those that are arranged for a connection to a premises wiring system from a portable alternate power supply.
Intent: The new sentence clarifies that Art. 702 applies to portable generators, which are commonly used for telecommunication facilities, water and wastewater pump stations, and backup power to homes and offices.
A temporary connection between any portable alternate power supply and the permanently installed premises wiring must comply with 527.2(C).
Intent: The new text alerts the reader that when a portable or vehicle-mounted generator provides temporary power and is connected to the permanent wiring system, a suitable means of transfer or isolation must be provided to prevent the inadvertent interconnection of normal and temporary power sources.
A transfer switch is required for all fixed or portable optional standby power systems for buildings or structures for which an electric-utility supply is either the normal or standby source.
Intent: Whenever a fixed or portable standby generator connects to premises wiring, you must have a transfer switch.
(A) Separately Derived Systems. If the transfer switch for a portable generator switches the grounded (neutral) conductor (separately derived system), then you must ground the portable generator in accordance with 250.30.
This new section means you must bond the case of the generator to the case, and you can use the building's grounding electrode for the generator.
(B) Nonseparately Derived System. If the transfer switch for a portable generator does not switch the grounded (neutral) conductor, then you must bond the equipment grounding conductor to the system grounding electrode.
This new section means the case of the generator must not be bonded to the case, but to a grounding electrode. You can use the building's grounding electrode for this purpose.
Intent: The new rule ensures portable generators are grounded properly. Effectively, this rule is only repeating the grounding requirements in Art. 250.
(A) Number and Size of Conductors in Raceway. The number and size of conductors in a raceway must be in accordance with the limitations listed in 300.17.
Intent: The new rule requires that the raceway fill limitations of 300.17 apply to Class 1, Class 2, and Class 3 conductors. When installing control and signaling cables in a raceway, you must limit the number in accordance with the percent fill limitations of Chapter 9, Table 1. The proposal that was submitted for this change was not intended to require Class 2 or Class 3 cables to comply with the raceway fill limitations [ROP 16-36], but the language has that effect. But this isn't important, because there is no physical way to install these cables anywhere near the 40% fill allowed in Chapter 9, Table 1 without destroying them.
Definitions for the following types of cable were added in several sections throughout Chapters 6, 7, and 8 — all of which state that if you do not terminate these cables at the equipment and identify them for future use with a tag, they will be considered abandoned:
640.2 Abandoned audio distribution cable
725.2 Abandoned Class 2, Class 3, and PLTC cable
760.2 Abandoned fire alarm cable
770.2 Abandoned optical fiber cable
800.2 Abandoned communications cable
820.2 Abandoned coaxial cable
830.2 Abandoned network-powered broadband communications cable
Requirements regarding the spread of fire or products of combustion were added in several sections throughout Chapters 6, 7, and 8 — all of which state you must remove the abandoned accessible portion of the following types of cables:
640.3 Audio distribution cable
725.3 Class 2, Class 3, and PLTC cables
760.3 Fire alarm cables
770.3 Optical fiber cables
800.52 Communications cable
820.3 Coaxial cables
830.2 Network-powered broadband communications cable
Intent: The new rules require you to remove “abandoned cables” to limit the spread of fire or products of combustion within a building. The rule does not require the removal of concealed cables abandoned in place.
Text was revised in several sections throughout Chapters 6, 7, and 8 regarding mechanical execution of work — stating you must install the following types of circuits in a neat and workmanlike manner. Cables installed exposed on the surface of ceilings and sidewalls must be supported by the structural components of the building in such a manner that the cable will not be damaged by normal building use. The following types of cables must be secured to structural components by straps, staples, hangers, or similar fittings designed and installed so as not to damage the cable:
725.6 Class 1, Class 2, and Class 3 cables
760.6 Fire alarm cables
770.8 Optical fiber cables
800.6 Communications cables
820.6 Coaxial cables
830.7 Network-powered broadband communications cable
840.6 Audio distribution cables
Intent: The revised text clarifies that cables must be properly secured and protected from physical damage in accordance with Sec. 300.4(D).
Chapter 9, Table 4 Dimensions and Percent Area of Conduit and Tubing
A 60% fill column was added for use with wire fill calculations for conduit or tubing nipples.
Intent: Note 4 to Table 1 of Chapter 9 identifies that where conduit or tubing nipples with a maximum length not exceeding 24 in. are installed between boxes, cabinets, and similar enclosures, the nipples are permitted to be filled to 60% of their total cross-sectional area. This new 60% column will be helpful when applying this requirement.
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