EC&M presents the third part in its 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 another installment in its 2002 NEC analysis. This month, we cover revisions to Chapter 5. (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.)

ARTICLE 500 — HAZARDOUS (CLASSIFIED) LOCATIONS

New definitions, some of which were contained in other Articles of the 1999 Code, have been added to the revised Article. They include dust-ignitionproof, dust-tight, electrical and electronic equipment, explosionproof apparatus, hermetically sealed, identified (as applied to equipment), nonhazardous locations, oil immersion, purged and pressurized, and unclassified locations.

Intent: Article 500 now provides a more logical sequence for Code rules for classification of locations and material groups, equipment protection techniques, equipment approvals, marking, and design.

ARTICLE 501 — CLASS I LOCATIONS

501.5 Sealing and Drainage

(A) Conduit Seals, Class I, Division 1

(4) Boundary Seal. A sealing fitting must be installed within 10 ft of either side of the boundary where a conduit leaves a Class I, Division 1 location. The sealing fitting must be designed and installed so as to minimize the amount of gas or vapor within the Division 1 portion of the conduit from being communicated beyond the seal. Except for listed explosionproof reducers at the conduit seal, there must be no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the Division 1 location.

Exception No. 2: Where the Class I, Division 1 boundary is beneath the ground, the sealing fitting can be installed after the conduit leaves the ground. Except for listed explosionproof reducers at the conduit seal, there must be no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the ground.

Intent: This exception clarifies where a seal fitting can be installed for underground conduit runs leaving a Class I, Division 1 location, when the boundary is beneath the ground.

ARTICLE 505 — CLASS I, ZONE 0, 1, AND 2 LOCATIONS

Article 505 was reorganized in a more logical sequence so the requirements for Zone Systems could stand alone, eliminating the need to reference other Articles for wiring requirements.

Article 505 Zone Systems for hazardous classified locations was added to the 1996 NEC. This system of wiring equipment in hazardous locations is based on the European Zone system, which was designed to keep electrical equipment out of the most hazardous areas. Most American manufacturers produce products listed for both Zone (Article 505) and Class I (Article 501) installations.

505.16 Sealing and Drainage

A new section covering the sealing and drainage requirements for conduits and cables in Zone-classified systems was added to the 2002 NEC. In the 1999 NEC, sealing and drainage requirements for Zone systems were contained in Sec. 501-5.

ARTICLE 511 — COMMERCIAL GARAGES, REPAIR, AND STORAGE

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

511.1 Scope

These occupancies must include locations used for service and repair operations in connection with self-propelled vehicles (including, but not limited to, passenger automobiles, buses, trucks, and tractors) in which volatile flammable liquids or flammable gases are used for fuel or power.

Intent: The additional text clarifies the requirements contained in Article 511 also apply to garages that repair vehicles powered by flammable gases such as compressed natural gas (CNG), liquefied natural gas (LNG), or liquefied petroleum gas (LPG), in addition to volatile flammable liquids (gasoline).

511.3 Classifications of Locations

(A) Unclassified Locations. Parking garages where no repair work is done except for the exchange of parts and routine maintenance requiring no use of electrical equipment, open flame, welding, or the use of volatile flammable liquids are not classified.

The storage, handling, or dispensing into motor vehicles of alcohol-based windshield washer fluid shall not cause the areas used for service and repair operations in connection with self-propelled vehicles to be classified as hazardous.

Intent: The additional text is intended to clarify the use of alcohol-based windshield washer fluid in service and repair garages does not cause the area to be classified as hazardous.

(B) Classified Locations

(1) Up to 18 in. Above the Floor. For each floor, the entire area up to a level of 18 in. above the floor shall be considered a Class I, Division 2 location.

Exception: The floor area shall not be classified if the authority having jurisdiction (AHJ) determines there is mechanical ventilation that provides a minimum of four air changes per hour or one cubic foot per minute of exchanged air for each square foot of floor area. Ventilation must provide for air exchange across the entire floor area within 12 in. of the floor.

Intent: The significant change was the clarification to the exception for determining what is adequate ventilation to change a Class I, Division 2 location to an unclassified area.

ARTICLE 514 — MOTOR FUEL DISPENSING FACILITIES

The title of this section was changed from Gasoline Dispensing and Service Stations to Motor Fuel Dispensing Facilities to recognize motor fuel would include compressed natural gas, liquefied natural gas, or liquefied petroleum gas. This Article was also reorganized to provide a common format and parallel numbering system for easier use. A new paragraph was added to separate and classify areas where compressed natural gas (CNG), liquefied natural gas (LNG), or liquefied petroleum gas (LPG) are stored, handled, or dispensed from motor fuel facilities.

Intent: These changes address area classification where CNG, LNG, and/or LPG is stored, handled, or dispensed at motor fuel dispensing facilities.

514.13 Provisions for Maintenance and Service of Dispensing Equipment

Each dispensing device must include a means of removing all external voltage sources, including feedback, during periods of maintenance and service of the dispensing equipment. This disconnecting means is not required to be inside or adjacent to the dispensing device.

Intent: The revised text clarifies the maintenance disconnect for the dispensing equipment need not be part of, or adjacent to, the dispenser.

ARTICLE 517 — HEALTH CARE FACILITY

517.3 Definitions

Health Care Facility. Buildings or portions of buildings in which medical, dental, psychiatric, nursing, obstetrical, or surgical care is provided. Health care facilities include, but are not limited to, hospitals, nursing homes, limited care facilities, clinics, medical and dental offices, and ambulatory care centers, whether permanent or movable.

Intent: This change aligns Article 517 with NFPA 99 — Health Care Facilities Code, and the new definition clarifies a health care facility includes buildings or portions of buildings in which psychiatric, nursing, obstetrical, or surgical care is provided.

517.13 Grounding of Receptacles and Fixed Electric Equipment in Patient Care Areas

Wiring in patient care areas must comply with (A) and (B) below:

(A) Wiring Methods. All branch circuits serving patient care areas must be installed in a metal raceway or cable that is listed in 250.118 as an acceptable grounding return path, such as EMT and/or Type AC cable.

(B) Insulated Equipment Grounding Conductor. In areas used for patient care, the grounding terminals of all receptacles and all noncurrent-carrying conductive surfaces of fixed electric equipment operating at over 100V, likely to become energized and subject to personal contact, must be grounded by an insulated copper equipment grounding conductor. The grounding conductor must be sized in accordance with Table 250.122, and it must be installed in a wiring method as identified in (A) above.

Intent: The NFPA Code committees completely revised this section to make it clear you can only use metal raceways or armored cables listed as a ground return path containing an insulated copper equipment grounding conductor for branch-circuit wiring supplying equipment, luminaires, and receptacles in patient care areas of health care facilities.

517.30 Essential Electrical Systems for Hospitals

(E) Receptacle Identification. The cover plates for receptacles, or receptacles supplied from the emergency system, must have a distinctive color or marking so as to be readily identifiable.

Intent: This change correlates with NFPA 99 — Health Care Facilities Code, which requires the identification (typically in red) of all emergency system receptacles in hospitals.

A new subsection, 517.41 Essential Electrical Systems for Nursing Homes and Limited Care Facilities, contains the same verbage.

ARTICLE 520 — THEATERS, AUDIENCE AREAS OF MOTION PICTURE AND TELEVISION STUDIOS, PERFORMANCE AREAS, AND SIMILAR LOCATIONS

520.1 Scope

This Article covers all buildings or that part of a building or structure, indoor or outdoor, designed or used for presentation, dramatic, musical, motion picture projection, or similar purposes and to specific audience seating areas within motion picture or television studios.

Intent: The additional text is intended to clarify that the requirements of Article 520 apply to both indoor and outdoor areas of a building or structure covered by this article.

520.5 Wiring Methods

(A) General. The wiring methods permitted in areas within the scope of Article 520 include fixed and flexible metal raceways, nonmetallic raceways encased in not less than 2 in. of concrete, MI, MC, or AC cable containing an insulated equipment grounding conductor.

Intent: The rule now permits you to install AC cable with an equipment grounding conductor in theaters, audience areas of motion picture and television studios, and performance areas.

ARTICLE 527 — TEMPORARY INSTALLATIONS

527.4 General

(J) Supports. Vegetation cannot be used for support of overhead spans of temporary wiring for branch circuits or feeders.

Intent: This new text clarifies that overhead temporary wiring cannot be supported by vegetation such as trees.

ARTICLE 547 — AGRICULTURAL BUILDINGS

547.2 Definitions

Distribution Point. An electrical supply point from which service drops, service laterals, feeders, or branch circuits to agricultural buildings, associated farm dwelling(s), and associated buildings under single management are supplied.

FPN No. 1: The Distribution Point is also known as the center-yard pole, meter pole, or the common distribution point.

FPN No. 2: The Service Point, as defined in Article 100, is typically at the Distribution Point.

Intent: This definition was relocated from 547-8(c) and revised to clarify the location of the disconnecting means for agricultural buildings as contained in 547.9.

Equipotential Plane. An area where wire mesh or other conductive elements are embedded in or placed under concrete, bonded to all metal structures and fixed nonelectrical equipment that may become energized to the grounding system. The purpose of the equipotential plane is to prevent a difference in voltage within the plane area.

Intent: This term was relocated from 547-9(a) and revised to clarify the equipotential plane requirements contained in 547.10.

547.5 Wiring Methods

(C) Equipment Enclosures, Boxes, Conduit Bodies, and Fittings

(1) Excessive Dust. Equipment enclosures, boxes, conduit bodies, and fittings installed in areas of agricultural buildings where excessive dust may be present must be designed to minimize the entrance of dust and have no openings (such as holes for attachment screws) through which dust could enter the enclosure.

(3) Corrosive Atmosphere. Where wet dust, excessive moisture, corrosive gases or vapors, or other corrosive conditions may be present in an agricultural building, equipment enclosures, boxes, conduit bodies, and fittings must have corrosion resistance properties suitable for the conditions.

Intent: The new text clarifies the conditions where the enclosures are installed dictate the types of enclosures required.

GFCI requirements for farm buildings were revised to read:

(G) Receptacles. All 15A and 20A, single-phase, 125V general-purpose receptacles installed in the locations specified below must have ground-fault circuit-interrupter protection for personnel.

  1. In areas having an equipotential plane [547.10(A)]

  2. Outdoors
  3. Damp or wet areas

Section 547.10(B) requires GFCI protection for all circuits providing electric power to equipment that is accessible to animals in dirt confinement areas.

Intent: The additional text clarifies GFCI protection is required for all general-purpose 15A and 20A, single-phase, 125V receptacles installed in areas having an equipotential plane, outdoors, or in wet areas of agricultural building.

The term “general purpose receptacles” is not defined in the NEC, but GFCI protection is not required for a receptacle installed for specific pieces of equipment such as brooders, incubators, feed mixers, feed grinders, or feed conveyors.

547.10 Equipotential Planes and Bonding of Equipotential Planes

The rules for equipotential planes were reorganized and rewritten to clarify where an equipotential plane is required and where it's not required. The revised rule is as follows:

(A) Areas Requiring Equipotential Planes. Equipotential planes must be installed in all concrete floor confinement areas of livestock buildings that contain metallic equipment that is accessible to animals and likely to become energized.

Outdoor concrete confinement areas, such as feedlots, must have equipotential planes installed around metallic equipment that is accessible to animals and likely to become energized. The equipotential plane must encompass the area around the equipment where the animal stands while accessing the equipment.

(B) Areas Not Requiring Equipotential Planes. Equipotential planes are not required in dirt confinement areas containing metallic equipment accessible to animals and likely to become energized. All circuits providing electric power to equipment that is accessible to animals in dirt confinement areas must have GFCI protection.

(C) Bonding. Equipotential planes must be bonded to the building or structure electrical grounding system. The bonding conductor shall be copper, insulated, covered or bare, and not smaller than 8 AWG. The 8 AWG bonding conductor must terminate to wire mesh or conductive elements of the equipotential plane by pressure connectors or clamps of brass, copper, copper alloy, or an equally substantial approved means.

FPN No. 1: Methods to establish equipotential planes are described in Equipotential Planes in Animal Containment Areas, American Society of Agricultural Engineers (ASAE) EP473-1997.

FPN No. 2: Low grounding electrode system resistances may reduce potential differences in livestock facilities.

Intent: The revisions clarify an equipotential plane is not required for indoor or outdoor dirt confinement areas, if GFCI protection is provided for electrical equipment accessible to animals in the confinement areas.

ARTICLE 555 — MARINAS AND BOATYARDS

Article 555 was rewritten so it incorporates the physical installation rules contained in NFPA 303 — Fire Protection Standard for Marinas and Boatyards.

555.1 Scope

This Article covers the installation of wiring and equipment in the areas comprising fixed or floating piers, wharfs, docks, and other areas in marinas, boatyards, boat basins, boathouses, and similar occupancies that are used, or intended for use, for the purpose of repair, berthing, launching, storage, or fueling of small craft and the moorage of floating buildings. Private, noncommercial docking facilities constructed or occupied for the use of the owner or residents of the associated single-family dwelling are not covered by this Article.

Intent: This clarifies Article 555 does not apply to boat docks at a single-family dwelling. Docking facilities at buildings containing more than one dwelling unit, such as duplexes, condominiums, and apartments fall under Article 555.

555.2 Definitions

Electrical Datum Plane. The electrical datum plane is defined as follows:

  1. Land areas subject to tidal fluctuation. The electrical datum plane is a horizontal plane 2 ft above the highest high tide level for the area occurring under normal circumstances.

  2. Land areas not subject to tidal fluctuation. The electrical datum plane is a horizontal plane 2 ft above the highest water level for the area occurring under normal circumstances.

Intent: The new definition and rules clarify when installing transformers [555.5], electrical connections [555.9], and receptacles [555.19] near water, you must take into consideration the highest water level for the areas under normal circumstances.

Marine Power Outlet. An enclosed assembly that can include receptacles, circuit breakers, fused switches, fuses, watt-hour meter(s), and monitoring means approved for marine use. All such enclosures must be arranged with a weep hole to discharge condensation.

Intent: The new definition is necessary for 555.19(A)(1) Shore Power Receptacles and 555.17(B) Disconnecting Means.

555.17 Boat Receptacle Disconnecting Means

(B) Location. The disconnecting means for a boat receptacle must be readily accessible not more than 30 in. from the receptacle. Circuit breakers or switches located in marine power outlets can be used for the boat receptacle disconnecting means.

Intent: This requirement was extracted from NFPA 303 — Fire Protection Standard for Marinas and Boatyards.

555.19 Boat Receptacle

(A) Boat Receptacles

(4) Ratings. Receptacles that provide shore power for boats must be rated not less than 30A and must be a single-outlet type.

(a) Receptacles rated 50A and less must be of the locking and grounding-type.

(b) Receptacles rated for 60A or 100A must be of the pin and sleeve type.

Intent: The new text clarifies the NEC does not contain any specific requirement that the rating of a receptacle be dependent upon the length of the boat. It sets a minimum rating of 30A and leaves it up to the designer to provide the receptacles they deem necessary based on projected usage of the ships.

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