EC&M presents the second in a four-part analysis of the most important revisions to the 1999 NEC.

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 second installment in its 2002 NEC analysis. This month, we cover revisions to Chapters 3 and 4. (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.)

Chapter 3

Art. 300 — Wiring Methods

300.1 Scope

(C) Metric Designators and Trade Sizes. Metric designators and trade sizes for conduit, tubing, and associated fittings and accessories are designated in Table 300.1(C).

Intent: The preceding metric designators were necessary because the NEC uses the metric system as the primary unit of measurement, as now required in 90.9. The metric units appear first throughout the NEC, and the inch-pound units follow in parentheses.

300.4 Protection Against Physical Damage

(B) Through Metal Framing Members.
(1) Nonmetallic-Sheath Cable (NM).
Where NM cables pass through factory or field opening in metal members, the NM cable must be protected by listed bushings or listed grommets that cover metal edges. The protection fitting must be securely fastened in the opening prior to installation of the cable.

Intent: The NFPA added the term “listed” to coordinate this section with 334.17, which now requires listed bushings or listed grommets to cover metal edges. The change was necessary because unlisted grommets and bushings may fall out.

300.5 Underground Installations

(K) Directional Boring. The Authority Having Jurisdiction (AHJ) must approve cables or raceways installed using directional boring equipment for this purpose.

Intent: As the frequency of directional boring installations has increased, so have the reports of elongations of continuous reeled raceways, which reduce the cross-sectional area of the raceway, and in some cases separate it. The requirement that the raceway be approved allows the AHJ to examine the installation and determine if any necking down or other damage may have occurred.

300.7 Raceways Exposed to Different Temperatures

The new NEC reworded the requirement for sealing against the flow of warm air to a colder section.

(A) Sealing. Where portions of a cable, raceway, or sleeve are known to be subjected to different temperatures and where condensation is known to be a problem (such as in cold storage areas of buildings or where the wiring passes from the interior to the exterior of a building), the raceway or sleeve must be filled with material approved by the AHJ to prevent the circulation of warm air to a colder section or sleeve. An explosionproof seal is not required to prevent the circulation of warm air to a colder section or sleeve.

Intent: The new wording better addresses the problem of heating and cooling energy loss (federal energy requirement) as well as condensation problems within raceways and enclosures when proper sealing is not provided. The last sentence clarifies you must use an approved material (not necessarily an explosionproof seal).

Art. 310 — Conductors for General Wiring

310.8 Locations

(D) Locations Exposed to Direct Sunlight. Insulated conductors and cables used where exposed to direct rays of the sun must be listed for sunlight resistance or listed and marked “sunlight resistant.”

Intent: The revised text clarifies the listing and/or marking requirements for conductors and cables exposed to direct sunlight. According to the UL White Book, conductors within SE cables must be suitable for direct rays of the sun. Due to rules in place by UL, you cannot market these conductors as “sunlight resistant.” However, single insulated conductors like THHN must be listed for sunlight resistance, and the “sunlight resistant” marking is optional. Keep in mind that THHN 2 AWG and larger (in the color black) is typically listed for sunlight resistance, and the conductor will be marked “sunlight resistant.”

310.15 Ampacities for Conductors

(B) Table 310.16 Ampacity.
(2) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a Raceway or Cable.
Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are stacked or bundled longer than 24 in. without maintaining spacing, the allowable ampacity of each conductor must be reduced as shown in Table 310.15(B)(2)(a).

Exception No. 5A: The ampacity adjustment factors of Table 310.15(B)(2)(a) do not apply to AC or MC cable without an overall outer jacket under the following conditions:

(a) Each cable has not more than three current-carrying conductors.
(b) The conductors are 12 AWG copper.
(c) No more than 20 current-carrying conductors are bundled or stacked.

Exception No. 5B: When more than 20 current-carrying conductors are bundled or stacked for more than 24 in., you must apply an ampacity adjustment factor of 60%.

Intent: The new exceptions (depending on the conditions) apply to 12 AWG AC or MC cable only without an outer cover. The new exception allows as many as 20 current-carrying conductors (for example, 10 two-wire cables or six three-wire cables) to be bundled without any ampacity adjustment. The second exception allows for an ampacity factor of only 60% if more than 20 current-carrying conductors (11 two-wire or seven three-wire cables, for example) are bundled together.

Art. 320 (333) — Armored Cable

320.30 Securing and Supporting

(B) Unsupported. AC cable can be unsupported where the cable is:

  1. Fished between concealed access points in finished buildings or structures and support is impracticable.

  2. Not more than 2 ft in length at terminals where flexibility is necessary.

  3. Not more than 6 ft from the last point of support within an accessible ceiling for the connection of luminaires.

Intent: The revised text permits you to run AC cable from lighting fixture to lighting fixture as long as the unsupported length of AC cable is not more than 6 ft.

Art. 330 (334) — Metal-Clad Cable

330.30 Securing and Supporting

(B) Unsupported. MC cable can be unsupported where the cable is:

  1. Fished between concealed access points in finished buildings or structures and support is impracticable.

  2. Not more than 2 ft in length at terminals where flexibility is necessary.

  3. Not more than 6 ft from the last point of support within an accessible ceiling for the connection of luminaires.

Intent: This new rule allows you to run MC cable from lighting fixture to lighting fixture as long as the unsupported length of MC cable is not more than 6 ft.

Art. 342 (345) — Intermediate Metal Conduit

342.30 Securing and Supporting

(B) Supports
(3) Exposed vertical risers for industrial machinery or fixed equipment can be supported at intervals not exceeding 20 ft, if the conduit is held up with threaded couplings, firmly supported at the top and bottom of the riser, and no other support means is available.

Intent: The additional words are intended to permit an expanded use of vertical risers to other equipment that is fixed in place. In addition, the change clarifies you can use vertical risers of IMC for fixed equipment in any occupancies, not just machinery in an industrial facility.

This change correlates with a change made with respect to Rigid Metal Conduit (RMC) in 344.30(B)(3).

Art. 362 (331) — Electrical Nonmetallic Conduit (ENT)

362.10 Uses Permitted

(2) In buildings exceeding three floors, you must install ENT concealed in walls, floors, or ceilings that provides a thermal barrier having a 15-min. finish rating as identified in listings of fire-rated assemblies.

Exception: When a building is supplied with an approved fire sprinkler system, you can install ENT exposed or concealed in buildings of any height.

Intent: The new exception permits ENT exposed or concealed in a fire-sprinklered building without the restriction of requiring a 15-min. finish rated thermal barrier.

(5) You can install ENT above a suspended ceiling if the suspended ceiling provides a thermal barrier having a 15-min. finish rating as identified in listings of fire-rated assemblies.

Exception: When a building is supplied with an approved fire sprinkler system, ENT can be installed above a suspended ceiling that does not have a 15-min. finish rated thermal barrier material.

Intent: The new exception permits ENT exposed or concealed above a suspended ceiling in a fire-sprinklered building without the restriction of requiring a 15-min. finish rated thermal barrier. 300.22(C)(1) does not allow nonmetallic raceways above suspended ceilings when that space is used for environmental air.

Art. 392 (318) — Cable Tray

392.3 Uses Permitted

You can use cable trays as a support system for services, feeders, branch circuits, communications circuits, control circuits, and signaling circuits. Cable tray installations are not to be limited to industrial establishments. Where exposed to direct rays of the sun, you must identify insulated conductors and jacketed cables as being sunlight resistant. The manufacturer must identify cable trays and their associated fittings for the intended use.

Intent: The additional wording clarifies you can use cable trays for the support of power, lighting, signaling, and communications circuits. Cable trays are manufactured in many forms, from a simple hanger or wire mesh to a substantial, rigid, steel support system. Cable trays are designed and manufactured to support a specific wiring method. To assure a safe support system, cable trays must be identified for their intended use.

392.6 Installation

(J) Raceways, Cables, and Boxes Supported from Cable Trays. In industrial facilities where conditions of maintenance and supervision ensure that only qualified persons will service the installation and where the cable tray system is designed and installed to support the load, you can use such cable tray systems to support raceways, cables, boxes, and conduit bodies.

For raceways terminating at the tray, you must use a listed cable tray clamp or adapter to securely fasten the raceway to the cable tray system. The raceway must be supported in accordance with the requirements of the appropriate raceway Article.

You can attach raceways or cables running parallel to the cable tray system to the bottom or side of a cable tray system. The raceway must be fastened and supported in accordance with the requirements of the appropriate raceway Article.

For boxes and conduit bodies attached to the bottom or side of a cable tray system, fastening and supporting must be in accordance with the requirements of Art. 314, specifically 314.23.

Intent: The revised text clarifies you can attach any size box, as well as conduit bodies, to the bottom or side of a cable tray system. And where raceways or cables are run parallel to and attached to the bottom or side of a cable tray system, the fastening and supporting must be in accordance with the requirements of the appropriate raceway or cable Article.

Chapter 4

Art. 400 — Flexible Cords and Cables

400.4 Types

Voltage ratings were added to Table 400-4.

Intent: Voltage markings on flexible cords and cables are optional. You can now find the voltage rating in this table when it is not marked on the flexible cord or cable.

400.7 Uses Permitted

(A) Uses. Flexible cords and cables must be used only for:
(2) Wiring of luminaires
(6) Connection of utilization equipment to facilitate frequent interchange.

Intent: The Code replaced the word “stationary” with “utilization.” The revised text clarifies you can use flexible cords for any utilization equipment to facilitate frequent interchange — whether or not the equipment is stationary.

400.8 Uses Not Permitted

Unless specifically permitted in 400.7, you cannot use flexible cords and cables for the following:

(5) Where concealed by walls, floors, or ceilings, or located above suspended or dropped ceilings.

Intent: The change clarifies flexible cords must be within sight (not concealed), because the cords might be subject to damage or fatigue that would not be readily detected.

Art. 404 (380) — Switches

404.9 Provisions for General Use Snap Switches

(B) Grounding. Snap switches, including dimmer and similar control switches, must be effectively grounded and must provide a means to ground metal faceplates, whether or not you install a metal faceplate. Snap switches must be considered effectively grounded according to (1) or (2) below.

  1. The switch is mounted with metal screws to a metal box or to a nonmetallic box with integral means for grounding devices.

  2. An equipment grounding conductor or equipment bonding jumper is connected to an equipment grounding termination of the snap switch.

Intent: This change clarifies fan control and other similar control switches, such as timers and dimmers, must be effectively grounded.

404.14 Rating and Use of Snap Switches (including dimmers)

(E) Dimmer. General use dimmer switches must only be used to control permanently installed incandescent luminaires unless otherwise listed for control of other loads, and installed accordingly.

Intent: This requirement is contained in the listing and installation instructions for dimmers. Inserting the text in the Code should help ensure that dimmers will be installed in accordance with the manufacturer/listing requirements. Dimmers are not listed to control a receptacle.

404.15 Switch Marking

(B) Off Indication. When in the OFF position, a switching device with a marked OFF position must completely disconnect all ungrounded (hot) conductors of the load it controls.

Intent: This rule requires switches with an OFF marking to disconnect all power. Where an electronic occupancy sensor is used, voltage will be present and a small current of 0.5 mA can flow — even when the switch is in the OFF position. This small amount of current can startle a person, perhaps causing a fall from a ladder. To solve this problem, manufacturers of wiring devices will most likely remove the word OFF from the switch.

Art. 406 — Receptacle, Cord Connectors, and Attachment Plugs (Caps)

NFPA added a new Article covering receptacles, cord connectors, and attachment plugs (caps).

Intent: This new Article contains the receptacle requirements formerly located in 210-7 and the receptacle, cord connector, and attachment plug requirements that were located in Part L of Art. 410 of the 1999 NEC. Consolidating the requirements for receptacles into one Article is part of the overall effort to make the Code more user-friendly.

406.8 Receptacles in Damp or Wet Locations

(A) Damp Locations. A receptacle installed outdoors in a location protected from the weather or in other damp locations must have an enclosure for the receptacle that is weatherproof when the receptacle is covered (attachment plug cap not inserted and receptacle covers closed).

An installation suitable for wet locations is also considered suitable for damp locations. A receptacle that is located outdoors is considered to be in a “location protected from the weather” if it is located under roofed open porches, canopies, marquees, and the like, and it is not subjected to beating rain or water runoff.

(B) Wet Locations

  1. 15A and 20A Outdoor Receptacles. 15A and 20A, 125V and 250V receptacles installed outdoors in a wet location must have an enclosure that is weatherproof when you insert the attachment plug.

  2. Other Receptacles. All other receptacles installed in a wet location must comply with (a) or (b):

(a) A receptacle installed in a wet location must have an enclosure that is weatherproof with the attachment plug cap inserted, if the equipment plugged into it is not attended while in use.

(b) A receptacle installed in a wet location must have an enclosure that is weatherproof when the attachment plug is removed, if the equipment plugged into it is attended while in use.

Intent: The revised text in (B)(1) is intended to ensure that all 15A and 20A, 125V and 250V receptacles installed outdoors in a wet location be within an enclosure and cover that is weatherproof at all times, even when you insert an attachment plug.

Art. 408 (384) — Switchboards and Panelboards

408.4 Circuit Directory

The purpose of all circuits must be legibly identified on a circuit directory on the face or inside of the panel door, and at each switch on a switchboard.

Intent: The new text clarifies all circuits must be properly identified. This includes each switch on a switchboard. See 110.22 for the revised requirements for the identification of disconnecting means.

408.21 Grounded Conductor Terminations

Each grounded (neutral) conductor must terminate within the panelboard in an individual terminal that is not also used for another conductor.

Intent: This new section should ensure the grounded (neutral) conductor would terminate within the panelboard in an individual terminal. This has been a UL requirement (UL Std. 67 — Panelboard Standard) for some time, but the NEC wanted to bring this information to the installer. Technically, this is covered by 110.3(B), which requires all equipment to be installed in accordance with the manufacturer's installation instructions and markings, but nobody knew it existed.

UL Std. 67 — Panelboard Standard permits up to three 10 AWG equipment grounding conductors to terminate in a single terminal, if the terminal is marked for this purpose.

The intent of this requirement is to ensure the grounded (neutral) conductor of a multiwire branch circuit is not momentarily disconnected, which could result in the destruction of electrical equipment and fires from overvoltage.

If two grounded (neutral) conductors are in the same terminal and someone removes one of the neutrals, the other neutral may be unintentionally removed as well. If that happens to the grounded (neutral) conductor of a multiwire circuit, it could result in excessive line-to-neutral voltage for one of the circuits. For example, if it was a 120V/240V multiwire circuit, with one circuit having a 24-ohm load and the other circuit having an 11.3-ohm load, a loose neutral could result in as much as 163V across a 120V load.

Art. 410 — Luminaires, Lampholders, and Lamps

The title of Art. 410 was changed from “Lighting Fixtures, Lampholders, Lamps, and Receptacles” to “Luminaires, Lampholders, and Lamps.” The title change was necessary because the term “luminaire” has replaced “fixture,” “lighting fixture,” and “lighting fixtures” throughout the NEC, and all of the receptacle requirements contained in Part L of Art. 410 in the 1999 NEC were relocated to a new Art. 406.

Intent: The change makes the Code suitable for international use and makes it easier to apply the requirements for receptacles.

Art. 430 — Motors

430.52 Rating or Setting for Individual Motor Circuit

Table 430-152 in the 1999 NEC, which contains the maximum rating or setting of motor branch-circuit, short-circuit, and ground-fault protective devices, was relocated to 430.52.

Intent: Relocating this table to 430.52 will make it easier to size motor branch-circuit protection devices.

430.62 Rating or Setting — Motor Load

(A) Specific Load. A feeder supplying a specific fixed motor load(s) and consisting of conductor sizes based on 430.24, must be provided with a protective device having a rating or setting not greater than the largest rating or setting of the branch-circuit, short-circuit, and ground-fault protective device for any motor supplied by the feeder based on the maximum permitted value for the specific type of a protective device in accordance with 430.52 and Table 430.52, or 440.22(A) for hermetic refrigerant motor-compressors, plus the sum of the full-load currents of the other motors of the group.

Intent: The change should make it clear that when sizing the feeder protection device for motors, the “maximum permitted value” for the largest branch-circuit protection device (BCPD) includes the exception of 430.52(C)(1) Exception No. 1, which permits the next higher standard-size rating where the values determined by Table 430-52 do not correspond to the standard sizes or ratings of fuses or circuit breakers as listed in 240.6(A).

IX. Disconnecting Means

430.102 Disconnect Means Location

(B) Motor Disconnect. A disconnecting means must be located in sight of the motor location and the driven machinery location. The controller disconnecting means, in accordance with 430.102(A), can serve as the disconnecting means for the motor, if the controller disconnect is located in sight of the motor location and the driven machinery location.

Exception: The motor disconnecting means is not required to be in sight of the motor and the driven machinery location under either condition (a) or (b) below, provided the controller disconnecting means required in accordance with 430.102(A) is capable of being individually locked in the open position. The provision for locking or adding a lock to the disconnecting means must be permanently installed on or at the switch or circuit breaker used as the controller disconnecting means.

(a) Where such a location of the disconnecting means is impracticable or introduces additional or increased hazards to persons or property.

(b) In industrial installations, with written safety procedures, where conditions of maintenance and supervision ensure only qualified persons will service the equipment.

FPN No. 1: Some examples of increased or additional hazards include, but are not limited to, motors rated in excess of 100 hp, multi-motor equipment, submersible motors, motors associated with variable frequency drives, and motors located in hazardous (classified) locations.

FPN No. 2: For information on lockout/tagout procedures, see Standard for Electrical Safety Requirements for Employee Workplaces, NFPA 70E-2000.

Intent: The revised subsection and exception are intended to improve worker safety by requiring the motor disconnecting means to be within sight of a motor and its driven machinery location as long as it does not add or increase hazards. There is much less chance that the worker will attempt to work when the equipment is “hot.” However, (b) of the exception recognizes that industrial establishments have a greater degree of control over the workplace, and those facilities that have an effective lockout/tagout program could use the exception. The exception also clarifies the provision for locking the disconnecting means for the controller must be permanently installed on or at the switch or circuit breaker used as the controller disconnecting means so an installer/maintainer can apply it and work safely.

Art. 440 — Air-Conditioning and Refrigerating Equipment

440.14 Location

Disconnecting means must be located within sight of and readily accessible from the air-conditioning or refrigerating equipment. You can install the disconnecting means on or within the air-conditioning or refrigerating equipment. The disconnecting means cannot be located on panels that are designed to allow access to the air-conditioning or refrigeration equipment.

Intent: Problems have been encountered in the field where someone installed the disconnecting means on the access panels of A/C and refrigeration equipment. This rule should take care of that potential problem.

Art. 445 — Generators

This Article was reorganized to provide a common format and parallel numbering of the Articles so it will be easier to use.

445.13 Ampacity of Conductors

The ampacity of the conductors from the generator terminals to the first distribution device(s) containing overcurrent protection cannot be less than 115% of the nameplate current rating of the generator.

Intent: The change clarifies conductors originating at the generator can terminate in equipment that has multiple overcurrent devices such as a distribution switchboard or panelboard, with or without a main overcurrent device.

When sizing conductors, you need to comply with all NEC requirements. 215.2(A)(1) requires all feeders to be sized no less than 125% of the continuous load. So if the generator supplies a continuous load, the conductors must be sized no smaller than 125% of the continuous load, but no less than 115% of the generator nameplate.

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