It's hard to believe it's that time again, but the 2008 NEC is upon us. In this latest Code cycle, the Code Making Panels (CMPs) sifted through 3,688 change proposals. Some of the resulting changes were minor editorial revisions. Others were more significant, such as new articles, sections, exceptions, and fine print notes.
Why does the NEC undergo revision every three years? For one thing, it must keep up with changes in methods and materials as technology marches forward. Other factors behind those 3,688 proposals include fire data and efforts to make the NEC more user-friendly.
Although we've highlighted what we consider to be the top 25 Code changes for the electrical industry in the following article, it's important to realize that this cycle produced hundreds of changes. Which ones really apply to the work you do? Use this simple three-step process to find the answer:
Review a sampling of typical jobs you completed over the past year.
Note which NEC requirements apply.
Look up those requirements in the 2008 NEC. Compare them to the 2005 requirements.
Now it's time to see what's new. Let's take a look at some important changes to the 2008 Code.
How to Use This Guide
Confused by all the different-looking text in this article? Refer to these descriptions to clear things up.
Each Code section that contains a change includes a summary of the change followed by a paraphrase of the NEC text affected by the change. Any specific change is denoted by blue text.
Author's comment is Mike Holt's opportunity to speak directly to you, in most cases offering insightful commentary and background on why the change was made.
Graphics with red borders contain a 2008 change; those without a red border support the concept discussed but nothing in the graphic was affected by a 2008 Code change.
- 100 — DEFINITION OF “GROUND”
The Grounding Task Group revised the definition for “ground” to improve the usability of the NEC.
or some conducting body that serves in place of the earth.
Author's comment: The revised definition is a good improvement because it provides a simple description. Previous language, “some conducting body that serves in place of the earth” was deleted, as the phrase left Code users wondering what “conducting body serving as a substitute for the earth” really was. Coordinating changes were made throughout the NEC to reflect the new definition.
- 100 — DEFINITION OF “NEUTRAL CONDUCTOR”
A new term, “neutral conductor,” was added to Art. 100.
The conductor connected to the neutral point of a system that is intended to carry current under normal conditions (click here to see Fig. 1).
Author's comment: The neutral conductor of a solidly grounded system is required to be grounded to the earth; therefore, this conductor is also called a “grounded conductor.” The 2005 NEC did not include a definition for “neutral conductor,” although it was used in many Articles. The lack of a definition of a term used throughout the Code caused confusion regarding the differences and similarities between the neutral conductor and the grounded conductor. Having a clear definition for the neutral conductor will help provide clarity in making this distinction.
This definition differentiates between the “neutral conductor” and the “equipment grounding conductor,” both of which are ultimately connected to the neutral point of a system. Under normal conditions, the “neutral conductor” is expected to be current-carrying, whereas the equipment grounding conductor is not.
Where necessary, rules throughout the NEC were revised to use the term “neutral conductor” or “neutral point” of a supply system. The term “neutral conductor” is intended to be used in conjunction with the new term “neutral point.”
- 100 — DEFINITION OF “NEUTRAL POINT”
A new term, “neutral point,” was added to Art. 100.
The common point on a 4-wire, 3-phase, 120/208V or 277/480V wye-connected system, the midpoint of a 3-wire, 120/240V single-phase system, or the midpoint of the single-phase portion of a 120/240V 3-phase delta-connected system (click here to see Fig. 2).
FPN: The potential of the vectorial sum of the nominal voltages from all other phases that utilize the neutral, with respect to the neutral point, is zero volts.
Author's comments: Rather than attempting to include all the concepts needed for the definition of the term “neutral” in a single definition, the Task Group of the Technical Correlating Committee chose to use two interdependent definitions. The definition of “neutral point” describes the point to which the neutral conductor is connected at the source.
- 210.4 — MULTIWIRE BRANCH CIRCUITS
The rule on “simultaneous disconnecting means” requirements for multiwire branch circuits was expanded.
(B) Disconnecting Means. Each multiwire branch circuit shall have a means to simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates (click here to see Fig. 3).
Author's comment: Multiwire branch circuits can offer unexpected shock hazards when work is being done on them — unless all ungrounded conductors from the multiwire branch circuit are disconnected simultaneously. This revised section requires each ungrounded conductor of a multiwire branch circuit to be disconnected simultaneously by common trip 2-pole or 3-pole circuit breakers or single-pole circuit breakers with an identified handle tie. Individual single-pole circuit breakers with handle ties identified for the purpose, or a breaker with a common internal trip, can be used for this application [240.15(B)(1)].
CAUTION: This rule is intended to prevent people from working on energized circuits they believe are disconnected.
- 210.4 — MULTIWIRE BRANCH CIRCUITS
A new subsection requires all conductors associated with a particular multiwire branch circuit to be physically grouped at the point of origin.
(D) Grouping. The ungrounded and neutral conductors of a multiwire branch circuit shall be grouped together in at least one location by wire ties or similar means at the point of origination (click here to see Fig. 4).
Exception: Grouping is not required where the circuit conductors are contained in a single raceway or cable that makes the grouping obvious.
Author's comment: Multiwire branch circuits offer the advantage of fewer conductors in a raceway, smaller raceway sizing, and a reduction of material and labor costs. In addition, multiwire branch circuits can reduce circuit voltage drop by as much as 50%. This new subsection requires that all associated conductors of a multiwire branch circuit be physically grouped together at least once with wire ties or other means within the panel or origination point of the circuit to make it easier to visually identify the conductors of the multiwire branch circuit. Grouping is intended to assist in terminating multiwire branch-circuit conductors to circuit breakers correctly, particularly where twin (tandem) breakers are used.
This new rule includes an exception that relaxes this requirement where the entry of the circuit conductors of a cable or raceway makes it obvious which conductors are associated with each other, without the need for additional grouping or tie wraps.
CAUTION: If care is not used when making these connections, two circuit conductors can be connected to the same phase conductor. If the ungrounded conductors of a multiwire circuit are not terminated to different phases, the currents on the neutral conductor will not cancel, but will add, which can cause an overload on the neutral conductor (click here to see Fig. 5).
Conductor overheating is known to decrease insulating material service life, which creates the potential for arcing faults in hidden locations and can ultimately lead to fires. It isn't known just how long conductor insulation lasts, but heat does decrease its life span.
If the continuity of the neutral conductor of a multiwire circuit is interrupted (open), the resultant over- or undervoltage can cause a fire and/or destruction of electrical equipment.
- 210.8 — GROUND-FAULT CIRCUIT-INTERRUPTER PROTECTION FOR PERSONNEL (GFCI)
Outdoor GFCI-protection requirements for 15A and 20A, 125V receptacles at nondwelling unit occupancies were revised.
(B) Other Than Dwelling Units
in public spaces. All 15A and 20A, 125V receptacles installed outdoors in public spaces — for the purpose of this section a public space is defined as any space that is for use by, or is accessible to the publicshall be GFCI-protected (click here to see Fig. 6).
Author's comment: The 2005 NEC only required 15A and 20A, 125V receptacles “outdoors in public spaces” to have GFCI protection. This change now requires GFCI protection for these types of receptacles installed at all outdoor locations, except as provided by the exceptions for snow-melting and deicing equipment and industrial establishments.
- 210.8 — GROUND-FAULT CIRCUIT-INTERRUPTER PROTECTION FOR PERSONNEL (GFCI)
A new subsubsection expands GFCI-protection requirements for 15A and 20A, 125V receptacles near sinks in nondwelling unit occupancies.
(B) Other Than Dwelling Units
(5) Sinks. All 15A and 20A, 125V receptacles installed within 6 ft of the outside edge of the sink shall be GFCI-protected (click here to see Fig. 7).
Exception No. 1: In industrial laboratories, receptacles used to supply equipment where removal of power would introduce a greater hazard can be installed without GFCI protection.
Exception No. 2: For receptacles located in patient care areas of health care facilities, other than those covered under 210.8(B)(1), GFCI protection shall not be required.
Author's comment: Sections 517.20 and 517.21 further modify the requirements for GFCI protection in health care facilities [90.3]. This new subsection is intended to require GFCI protection near sinks for nondwelling units. Exception No. 1 was added for industrial laboratories where the tripping of a GFCI will introduce a greater hazard. The AHJ will need to interpret and apply this rule since no explanation is provided as to what constitutes a “greater hazard.”
Exception No. 2 leaves the requirement for GFCI protection of receptacles installed in bathroom areas of health care facilities in place [210.8(B)(1)], but excludes the GFCI-protection requirement if located near the sinks in patient care areas of health care facilities.
- 210.12 — ARC-FAULT CIRCUIT-INTERRUPTER PROTECTION (AFCI)
AFCI-protection requirements for 15A and 20A, 120V dwelling unit circuits were expanded again.
(B) Dwelling Units. All 15A or 20A, 120V branch circuits that supply outlets in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways or similar areas shall be protected by a listed AFCI device of the combination type (click here to see Fig. 8).
Author's comment: The 120V circuit limitation means AFCI protection isn't required for equipment rated 230V, such as baseboard heaters or room air conditioners.
Supporters asserted that AFCIs have had an excellent track record in the field, and that both wiring errors and wiring damage have been found through the installation of AFCIs, reducing potential sources of electrical fires. Opponents asserted that combination AFCIs have no track record at all and that this change will result in high costs to consumers, estimated by at least one source to exceed $2.1 billion annually. Opponents do not believe there was sufficient documentation to support the expansion of AFCI requirements in the 2008 NEC. The 2008 NEC requirement does not require AFCI protection in rooms or areas where GFCI protection of receptacle outlets is required. Though not required by the Code, both AFCI and GFCI protection can be provided for the same branch circuits or receptacle outlets, as the different protection technologies are compatible.
In addition, a new Fine Print Note clarified dwelling unit AFCI-protection requirements of fire alarm circuits, and the rules on locating the AFCI device were rewritten to relax the restrictions.
FPN No. 3: See 760.41 and 760.121 for power-supply requirements for fire alarm systems.
Author's comment: Smoke alarms connected to a 15A or 20A circuit must be AFCI-protected if the smoke alarm is located in the bedroom of a dwelling unit. The exemption from AFCI protection for the “fire alarm circuit” contained in 760.41 and 760.121 doesn't apply to the single and multiple station smoke alarm circuit typically installed in dwelling unit bedroom areas. This is because a smoke alarm circuit isn't a fire alarm circuit as defined in NFPA 72, National Fire Alarm Code. Unlike single and multiple station smoke alarms, fire alarm systems are managed by a fire alarm control panel. (click here to see Fig. 9)
Exception No. 1: The AFCI-protection device can be located at the first outlet if the circuit conductors are installed in RMC, IMC, EMT or steel Type AC, and the AFCI device is contained in a metal outlet or junction box.
Author's comment: Type MC cable without a bare aluminum grounding/bonding conductor does not fall within the scope of this exception because the armor cable is thinner than that of Type AC cable.
Exception No. 2: AFCI protection can be omitted for branch- circuit wiring to a fire alarm system in accordance with 760.41(B) and 760.121(B), if the circuit conductors are installed in RMC, IMC, EMT, or steel armored Type AC cable.
Author's comment: The new fine print note is intended to alert Code users to the fact that AFCI protection is not required for the “fire alarm circuit,” but caution must be exercised because 760.41 and 760.121 don't apply to the single and multiple station smoke alarm circuit typically installed in dwelling unit bedroom areas! This is because a smoke alarm circuit isn't a fire alarm circuit as defined in NFPA 72, National Fire Alarm Code. Unlike single and multiple station smoke alarms (smoke detectors), fire alarm systems are managed by a fire alarm control panel, which qualifies it as a fire alarm system.
Exception No. 1 in the 2005 NEC required that the circuit conductors to the AFCI device be no longer than 6 ft in order to use an AFCI device not located in the panelboard. Because of this stringent requirement, no manufacturer produced a stand-alone AFCI device. Manufacturers indicated that they would make the product available in a receptacle form if there were enough demand, and believed that the exception in the 2005 NEC was written in a way that stifled demand. The 2008 exception allows the AFCI device to be located any distance from the panelboard, so long as the specified wiring methods are used to protect against physical damage.
- 240.24 — LOCATION OF OVERCURRENT DEVICES
A new subsection addresses the installation of overcurrent devices in stairways.
(F) Not Located Over Steps. Overcurrent devices shall not be located over steps of a stairway (click here to see Fig. 10).
Author's comment: This change prohibits the installation of overcurrent devices over steps in stairways. Clearly, it's difficult for electricians to safely work on electrical equipment that is located on uneven surfaces such as over stairways. However, such overcurrent devices can be located over landings adjacent to stairways.
- 250.4 — GENERAL REQUIREMENTS FOR GROUNDING AND BONDING
A new Fine Print Note alerts Code users to the advantage of reducing the length of the grounding electrode conductor.
(A) Grounded Systems
(1) Electrical System Grounding. Electrical power systems, such as the secondary winding of a transformer, are grounded to the earth to limit the voltage caused by lightning, line surges, or unintentional contact by higher-voltage lines.
FPN: An important consideration for limiting the imposed voltage is the routing of bonding and grounding conductors so that they are not any longer than necessary to complete the connection without disturbing the permanent parts of the installation and so that unnecessary bends and loops are avoided (click here to see Fig. 11).
Author's comment: System grounding helps reduce fires in buildings as well as voltage stress on electrical insulation, thereby ensuring longer insulation life for motors, transformers, and other system components. This new Fine Print Note is intended to call attention to the instructions contained in Secs. 800.100(A)(5), 810.21(E), and 820.100(A)(5) that grounding conductors be run as short as possible and as straight as possible. This provides an effective path to the earth for line surges caused by lightning events.
- 250.32 — BUILDINGS OR STRUCTURES SUPPLIED BY FEEDER OR BRANCH CIRCUIT
The rule that permitted the regrounding of the neutral conductor at separate buildings and structures was deleted.
(B) Equipment Grounding Conductor. To quickly clear a ground fault and remove dangerous voltage from metal parts, the building or structure disconnecting means shall be connected to the circuit equipment grounding conductor of a type described in 250.118. Where the supply circuit equipment grounding conductor is of the wire type, it shall be sized to 250.122, based on the rating of the supply circuit overcurrent device rating (click here to see Fig. 12).
Exception: For existing premises, when an equipment grounding conductor was not run to the building or structure disconnecting means, the building or structure disconnecting means can remain connected to the neutral conductor where there are no continuous metallic paths between buildings and structures, ground-fault protection of equipment isn't installed on the supply side of the circuit, and the neutral conductor is sized no smaller than the larger of:
The maximum unbalanced neutral load in accordance with 220.61.
The rating of the circuit overcurrent device, in accordance with 250.122.
Caution: To prevent dangerous objectionable neutral current from flowing onto metal parts [250.6(A)], the supply circuit neutral conductor is not permitted to be connected to the remote building or structure disconnecting means [250.142(B)] (click here to see Fig. 13).
Author's comment: In the 2005 NEC, 250.32(B)(2) permitted the neutral conductor to serve as the effective ground-fault current path. This rule was converted into an exception for existing premises. Using the neutral conductor to connect metal objects to the effective ground-fault current path is a dangerous practice, especially if the neutral becomes open.
- 250.52 — GROUNDING ELECTRODES
The requirements for a concrete-encased electrode now include vertical electrodes as well as what to do when multiple isolated concrete-encased electrodes are present.
(A) Electrodes Permitted for Grounding.
(3) Concrete-Encased Grounding Electrode. A concrete-encased electrode is an electrode that is encased by at least 2 in. of concrete, located horizontally near the bottom or vertically within a concrete foundation or footing that is in direct contact with the earth consisting of one of the following (click here to see Fig. 14):
Twenty feet of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars bonded together by the usual steel tie wires not less than ½ in. in diameter, or
Twenty feet of bare copper conductor not smaller than 4 AWG.
Author's comment: If a moisture/vapor barrier is installed under a concrete footer, then the steel rebar is not considered a concrete-encased electrode.
Where multiple concrete-encased electrodes are present at a building or structure, only one is required to serve as the grounding electrode system (click here to see Fig. 15).
The grounding electrode conductor to a concrete-encased grounding electrode isn't required to be larger than 4 AWG copper [250.66(B)].
The concrete-encased grounding electrode is also called a “Ufer Ground,” named after Herb Ufer, the person who determined its usefulness as a grounding electrode in the 1960s. This type of grounding electrode generally offers the lowest ground resistance for the cost.
The requirements for concrete-encased electrodes have been expanded to allow structural steel rebar in vertical foundations to be suitable as a grounding electrode, as long as it meets all of the requirements for horizontal structural steel rebar electrodes. In addition, the 2008 NEC clarified that in a building or structure where multiple isolated concrete-encased electrodes are present, such as for spot footings, only one of these “present” electrodes will be required to be used. The purpose of the NEC [90.1] is the “practical safeguarding of persons and property,” and requiring all of the concrete-encased electrodes to be bonded together served no safeguarding purpose.
- 250.94 — INTERSYSTEM BONDING TERMINAL
A new rule requires an intersystem bonding terminal for communications systems.
An external accessible intersystem bonding terminal for the grounding and bonding of communications systems shall be provided at service equipment and disconnecting means for buildings or structures supplied by a feeder (click here to see Fig. 16).
The intersystem bonding terminal shall not interfere with the opening of any equipment enclosure and be one of the following:
Terminals listed for grounding and bonding attached to a meter socket enclosure.
Bonding bar connected to the equipment grounding conductor with a minimum 6 AWG copper conductor.
Bonding bar connected to the grounding electrode conductor with a minimum 6 AWG copper conductor.
Author's comment: According to Art. 100, an intersystem bonding terminal is a device that provides a means to connect communications systems grounding and bonding conductors to the building grounding electrode system.
Exception: At existing buildings or structures, an external accessible means for bonding communications systems together can be:
- Nonflexible metallic raceway,
- Grounding electrode conductor, or
- Connection approved by the authority having jurisdiction.
FPN No. 2: Communications systems shall be bonded to the intersystem bonding terminal in accordance with the following:
- Antennas/Satellite Dishes, 810.15 and 810.21
- CATV, 820.100
- Telephone Circuits, 800.100
Author's comment: All external communications systems must be bonded to the intersystem bonding terminal to minimize the damage to communications systems from induced potential (voltage) differences between the systems from a lightning event.
This is one of several correlated proposals to improve the requirements related to the intersystem bonding and grounding of communications systems. This provides a more accessible, safer means of bonding all systems, such as power and communications, together.
- 250.146 — CONNECTING RECEPTACLE GROUNDING TERMINAL TO BOX
A new sentence adds bonding requirements for receptacles attached to exposed work covers.
(A) Surface-Mounted Box.
An equipment bonding jumper is not required for receptacles attached to listed exposed work covers when the receptacle is attached to the cover with two permanent fasteners (rivets), or have a threaded or screw locking means; and the cover mounting holes are located on a flat non-raised portion of the cover (click here to see Fig. 17).
Author's comment: This rule was added because exposed work covers with two fasteners to attach the receptacle to the cover are listed as a suitable bonding means.
- 310.15 — AMPACITIES FOR CONDUCTORS RATED 0 TO 2,000V
A new subsection adds ambient temperature adjustments for conduits installed on rooftops.
(2) Adjustment Factors
(c) Raceways Exposed to Sunlight on Rooftops. The ambient temperature adjustment contained in Table 310.15(B)(2)(c) is added to the outdoor ambient temperature for conductors or cables that are installed in raceways exposed to direct sunlight on or above rooftops when applying ampacity adjustment correction factors contained in Table 310.16.
FPN No. 1: See ASHRAE Handbook-Fundamentals (www.ashrae.org) for the average ambient temperatures in various locations.
FPN No. 2: The temperature adders in Table 310.15(B)(2)(c) are based on the results of averaging the ambient temperatures.
Table 310.15(B)(2)(c) Ambient Temperature Adjustments for Raceways Exposed to Sunlight On or Above Rooftops Distance Above Roof Temperature Added to Bottom of Conduit °C °F 0 in. to ½ in. 33 60 Above ½ in. to 3½ in. 22 40 Above 3½ in. to 12 in. 17 30 Above 12 in. to 36 in. 14 25
Author's comment: When adjusting conductor ampacity, use the conductor ampacity as listed in Table 310.16, based on the conductor's insulation rating. In this case, it's 75A at 90°F. Conductor ampacity adjustment is not based on the temperature terminal rating as per 110.14(C).
This new subsection requires the ambient temperature used for ampacity correction to be adjusted where conductors or cables are installed in conduit on or above a rooftop, and the conduit is exposed to direct sunlight. The reasoning behind this change is that the air inside conduits in direct sunlight is significantly hotter than the surrounding air, and appropriate ampacity corrections must be made in order to comply with 310.10.
- 406.8 — RECEPTACLES IN DAMP OR WET LOCATIONS
Receptacles installed in wet locations are now required to be weather resistant.
(B) Receptacles in Wet Locations.
(1) 15A and 20A Receptacles. All 15A and 20A receptacles installed in a wet location shall be within an enclosure that is weatherproof when an attachment plug is inserted, and all nonlocking 15A and 20A, 125V and 250V receptacles in a wet location shall be listed as weather resistant (click here to see Fig. 18).
Exception: Receptacles subject to routine high-pressure washing spray may have an enclosure that is weatherproof when the attachment plug is removed.
Wet locations are those subject to saturation with water, and unprotected locations exposed to weather [Art. 100].
Exposed plastic surface material of weather-resistant receptacles must have UV resistance to ensure deterioration from sunlight does not take place or is minimal. In testing, receptacles are subjected to temperature cycling from very cold to very warm conditions and then additional dielectric testing. The rapid transition from the cold to warm temperature will change the relative humidity and moisture content on the device and the dielectric test ensures that this will not present a breakdown of the insulation properties.
The change to this subsection was made in response to concerns that receptacles located outdoors are not always protected from detrimental conditions such as low temperatures, exposure to ultraviolet radiation (UV), physical damage, etc., and that weatherproof covers and enclosures do not always provide sufficient protection from the elements. The new exception allows receptacle covers in high-pressure spray washing areas to be of the type that is weatherproof when the attachment plug is removed. When a weatherproof while-in-use cover is used with high-pressure spray cleaning, liquid can spray into the enclosure through the cable openings. This change allows the use of a snap cover that does not have a cable opening in it while closed.
- 406.11 — TAMPER-RESISTANT RECEPTACLES IN DWELLING UNITS
Requirements for tamper-resistant receptacles were added to the 2008 NEC.
In dwelling units, all 15A and 20A, 125V receptacles shall be listed as tamper resistant.
Author's comment: This rule applies to receptacles installed behind appliances, above countertops, and other locations out of the reach of children.
This new section requires the use of listed tamper-resistant receptacles for all 15A and 20A, 125V receptacles installed in dwelling units.
- 422.52 — ELECTRIC DRINKING FOUNTAINS
GFCI protection for electric drinking fountains was added.
Electric drinking fountains shall be connected to a GFCI-protected outlet.
Author's comment: This new requirement was brought about without documentation of an electrical accident or incident.
- 522 — CONTROL SYSTEMS FOR PERMANENT AMUSEMENT ATTRACTIONS
A new Article addressing Control Systems for Permanent Amusement Attractions was added.
This new Article covers the installation of control circuit power sources and control circuit conductors for electrical equipment, in or on all structures that are an integral part of a permanent amusement attraction. The Article is divided into three parts:
- Part I. General
- Part II. Control Circuits
- Part III. Control Circuit Wiring Methods
Author's comment: This new article was created because theme parks bring together a unique combination of rides, show elements, transportation, theaters, other facilities, live shows, and new technologies.
- 626 — ELECTRIFIED TRUCK PARKING SPACE EQUIPMENT
A new Article addressing Electrified Truck Parking Space Equipment was added.
This new Article covers the electrical conductors and equipment external to the truck or transport refrigerated unit that connect trucks and transport refrigerated units to a supply of electricity, and the installation of equipment and devices related to electrical installations within an electrified truck parking space.
A truck parking space is a location with an electrical system that allows truckers to “plug in” their vehicles while stopped, and use off-board power sources in order to operate onboard systems such as air-conditioning, heating, and appliances, without any engine idling.
An electrified truck parking space may also include dedicated parking areas for heavy-duty trucks at travel plazas, warehouses, shipper and consignee yards, depot facilities, border crossings, etc. It does not include areas such as the shoulders of on and off highway ramps and access roads, camping and recreational vehicle sites, residential and commercial parking areas used for automotive parking or other areas where AC power is provided solely for the purpose of connecting automotive and other light electrical loads, such as engine block heaters, and at private residences.
Author's comment: This new Article covers the electrical installation requirements for conductors and equipment that connect trucks and transport refrigerated units to electric power within an electrified parking space.
This issue was driven by the U.S. Environmental Protection Agency (EPA), which has been pressing the transportation industry to reduce the idling of trucks at truck stops so as to reduce air pollution and the use of millions of gallons of fuel each year. The intent of this article is to provide an electrical standard for the transportation industry.
- 680.26 — EQUIPOTENTIAL BONDING
The bonding rules for reducing voltage gradients around permanently installed pools, outdoor spas, or outdoor hot tubs were changed again.
(A) Performance. Equipotential bonding is intended to reduce voltage gradients in the area around permanently installed pools, outdoor spas, or outdoor hot tubs by the use of a common bonding grid in accordance with 680.26(B) and (C).
(B) Bonded Parts. The parts of a permanently installed pool, outdoor spa, or outdoor hot tub listed in (B)(1) through (B)(7) shall be bonded together with a solid copper conductor not smaller than 8 AWG with listed pressure connectors, terminal bars, exothermic welding, or other listed means [250.8(A)] (click here to see Fig. 19).
Equipotential bonding is not required to extend to or be attached to any panelboard, service equipment, or grounding electrode.
Conductive Pool, Outdoor Spa, and Outdoor Hot Tub Shells.
(a) Structural Reinforcing Steel. Unencapsulated structural reinforcing steel secured together by steel tie wires is considered bonded.
Perimeter Surfaces. An equipotential bonding grid shall extend 3 ft horizontally beyond the inside walls of a pool, outdoor spa, or outdoor hot tub, including unpaved, paved, and poured concrete surfaces (click here to see Fig. 20).
The bonding grid shall comply with (a) or (b) and be attached to the conductive pool reinforcing steel at a minimum of four points uniformly spaced around the perimeter of the walls of a pool, outdoor spa, or outdoor hot tub.
(a) Structural Reinforcing Steel. Structural reinforcing steel [680.26(B)(1)(a)] (click here to see Fig. 21).
Author's comment: The 2008 NEC does not provide any guidance on the installation requirements for structural reinforcing steel when used as a perimeter equipotential bonding grid.
(b) Alternate Means. Equipotential bonding conductor meeting the following (click here to see Fig. 22):
8 AWG bare solid copper bonding conductor.
The bonding conductor shall follow the contour of the perimeter surface.
Listed splicing devices.
Bonding conductor shall be 18 to 24 in. from the inside walls of the pool.
Bonding conductor shall be secured within or under the perimeter surface 4 to 6 in. below the subgrade.
(3) Metallic Components. Metallic parts of the pool, outdoor spa, or outdoor hot tub structure shall be bonded to the equipotential grid.
(4) Underwater Metal Forming Shells. Metal forming shells and mounting brackets for luminaires and speakers shall be bonded to the equipotential grid.
(5) Metal Fittings. Metal fittings sized 4 in. and larger that penetrates into the pool, outdoor spa, or outdoor hot tub structure, such as ladders and handrails shall be bonded to the equipotential grid.
(6) Electrical Equipment. Metal parts of electrical equipment associated with the pool, outdoor spa, or outdoor hot tub water circulating system, such as water heaters, pump motors, and metal parts of pool covers shall be bonded to the equipotential grid (click here to see Fig. 23).
Exception: Metal parts of listed equipment incorporating an approved system of double insulation is not required to be bonded to the equipotential grid.
(a) Double-Insulated Water Pump Motors. Where a double-insulated water-pump motor is installed, a solid 8 AWG copper conductor from the bonding grid shall be provided for a replacement motor.
(b) Pool Water Heaters. Pool water heaters shall be grounded and bonded in accordance with equipment instructions.
(7) Metal Wiring Methods and Equipment. Metal-sheathed cables and raceways, metal piping, and all fixed metal parts shall be bonded to the equipotential grid.
Exception No. 1: Where separated from the pool, outdoor spa, or outdoor hot tub structure by a permanent barrier.
Exception No. 2: Where located more than 5 ft horizontally of the inside walls of the pool, outdoor spa, or outdoor hot tub structure.
Exception No. 3: Where located more than 12 ft measured vertically above the maximum water level.
(C) Pool Water. A minimum conductive surface area of 9 sq in. shall be installed in contact with the pool, outdoor spa, or outdoor hot tub structure water. This water bond is permitted to consist of metal parts that are bonded in 680.26(B).
Author's comment: This section was completely rewritten to clarify equipotential bonding requirements for permanently installed pool, outdoor spa, or outdoor hot tub areas.
- 700.9 — WIRING
The rules on “emergency circuits independent of all other wiring” when a single generator supplies emergency, legally required, and/or optional loads were clarified.
(B) Wiring. To ensure that a fault on the normal wiring circuits will not affect the performance of emergency wiring or equipment, all wiring to emergency loads shall be kept entirely independent of all other wiring, except:
Wiring in transfer equipment.
Luminaires supplied from two sources of power.
Junction box attached to luminaires supplied from two sources of power.
Wiring within a common junction box attached to unit equipment, containing only the branch circuit supplying the unit equipment and the emergency circuit supplied by the unit equipment.
Wiring from an emergency source is permitted to supply any combination of emergency, legally required, or optional loads in accordance with the following:
a. From separate vertical switchboard sections or from individual disconnects mounted in separate enclosures.
b. By single or multiple feeders without overcurrent protection at the source.
c. Legally required and optional standby circuits shall not originate from the same vertical switchboard section, panelboard enclosure, or disconnect as emergency circuits.
Author's comment: New subsection to clarify that separation of the circuits served by a generator source for emergency, legally required, and optional circuits may be accomplished by running feeders from a single generator to individual overcurrent devices or to a distribution switchboard that separates emergency circuits in different vertical sections from other loads.
- 702.5 — CAPACITY AND RATING
The sizing for Optional Standby Power Systems is now based on the type of transfer switch used; manual versus automatic.
(A) Available Short-Circuit Current. Optional standby system equipment shall be rated for the maximum available short-circuit current at its terminals.
(B) System Capacity. The calculated load on the standby source shall be in accordance with Art. 220 or by a method approved by the authority having jurisdiction.
(1) Manual Transfer Equipment. The optional standby power source shall have adequate capacity for all equipment intended to operate at one time. The user of the optional standby system selects the loads to be connected to the system.
Author's comment: When a manual transfer switch is used, the user of the optional standby system selects the loads to be connected to the system, which determines the system size.
(2) Automatic Transfer Equipment.
(a) Full Load. The optional standby power source shall have adequate capacity to supply the full load transferred.
Author's comment: If an automatic transfer switch is used in an optional system, the power source — typically a generator — must be capable of supplying the full load transferred. The load is determined by using Art. 220 as a basis on system sizing or an alternate method approved by the AHJ.
For existing facilities, the optional standby source can be sized to the maximum demand data available for one year or the average power demand of a 15-minute period over a minimum of 30 days [220.87].
This section was extensively revised and new subsections added in response to the growth of generator installations and the concern about the sizing of an optional standby source that uses automatic transfer switching.
If an automatic transfer switch is used in an optional system, the power source — typically a generator — must be capable of supplying the full load transferred. The load is determined by using Art. 220 as a basis on system sizing or an alternate method approved by the AHJ. However, the conditions are not the same for optional standby power supply when a manual transfer switch is used. In this case, the user of the optional standby system selects the loads to be connected to the system, which determines the system size.
- 708 — CRITICAL OPERATIONS POWER SYSTEMS
A new article addressing Critical Operations Power Systems was added to the 2008 NEC.
The provisions of this article apply to the installation, operation, monitoring, control, and maintenance of premises wiring intended to supply, distribute, and control electricity to designated critical operations areas in the event of disruption to elements of the normal system.
Critical operations power systems are those systems so classed by municipal, state, federal, or other codes, by any governmental agency having jurisdiction, or by facility engineering documentation establishing the necessity for such a system. These systems include but are not limited to power systems, HVAC, fire alarms, security, communications, and signaling for designated critical operations areas.
Critical Operations Power Systems are generally installed in vital infrastructure facilities that, if destroyed or incapacitated, will disrupt national security, the economy, public health or safety; and where enhanced electrical infrastructure for continuity of operation is deemed necessary by governmental authority.
Threats to facilities that may require transfer of operation to the critical systems include both naturally occurring hazards and human-caused events.
Author's comment: Recent terrorist events and natural disasters, such the World Trade Center attack and Hurricane Katrina, highlighted the need to assess the adequacy of the National Electrical Code requirements for electrical infrastructure protection and reliability. This new Article 708 was created by a task group that was established in response to Homeland Security activity and specifically directed to set rules on how to keep an emergency system operating for days. The task group was formed to review requirements in the NEC and other NFPA codes and standards covering emergency and standby power systems and sources and signaling systems.
- 800.156 — DWELLING UNIT COMMUNICATIONS OUTLET
A new section was added addressing communications outlets within dwelling units.
No less than one communications outlet shall be installed within each dwelling unit (click here to see Fig. 24).
Author's comment: This section was added to require that a communications outlet be provided at the location of the communications service entrance to a dwelling for new construction. There was previously no requirement for this.
Sidebar: The Change Process
It takes about two years to complete each NEC change cycle. Let's take a quick look at this 10-step process, with dates included for the 2008 cycle:
Step 1. Submit Proposals. November 2005. Anybody can submit a proposal to change the Code before the proposal closing date.
Step 2. Review Proposals. January 2006. The 20 CMPS in the 2008 Code revision process voted to accept, reject, or modify the proposals.
Step 3. Publish Report on Proposals (ROP). July 2006. The ROP is a document for public review, which contains the results of Step 2.
Step 4. Submit ROP Comments. October 2006. Members of the public submitted their feedback on the ROP, asking CMPs to revise their earlier actions on change proposals.
Step 5. Review ROP Comments. December 2006. The CMPs met again to review, discuss, and vote on public comments.
Step 6. Report on Comments (ROC). April 2007. The voting on the “Comments” was published for public review in a document called the “Report on Comments,” frequently referred to as the “ROC.”
Step 7. Review at Electrical Section. June 2007. The NFPA Electrical Section discussed and reviewed the work of the CMPs. The Electrical Section developed recommendations on last-minute motions to revise the proposed NEC draft that would be presented at the NFPA annual meeting.
Step 8. Adopt at NFPA Annual Meeting. June 2007. The 2008 NEC was officially adopted at the annual meeting, after several motions (often called “floor actions”) were voted on.
Step 9. Approve the 2008 NEC. July 2007. The NFPA Standards Council reviewed the record of the Code-making process and approved publication of the 2008 NEC.
Step 10. Publish 2008 NEC. September 2007. The 2008 National Electrical Code was published, following NFPA Board of Directors review of appeals.