11.4 Garages, Hangars, Fuel Dispensing, Bulk Storage and Spray Application

Article 511 — Commercial Garages, Repair and Storage

511.1 Scope. Article 511 applies to locations used for service and repair operations in connection with self-propelled vehicles in which volatile flammable liquids or flammable gases are used for fuel or power.

511.2 distinguishes a major repair garage — where major repairs such as engine overhauls, painting, body and fender work, and repairs that require draining of the fuel tank are performed — from a minor repair garage, where lubrication, inspection, and minor routine maintenance are performed.

511.3 Area Classification. Where flammable liquids having a flash point below 38 degrees C (100 degrees F), such as gasoline, are used, the classification is determined by Table 511.3(C) for major repair garages and Table 511.3(D) for minor repair garages.

For a major repair garage where ventilation is not provided:

Where ventilation is provided — mechanical ventilation providing a minimum of 4 air changes per hour or 1 cubic foot per minute per square foot of floor area, with exhaust taken from a point within 18 inches of the floor — the floor-to-18-inch area is unclassified.

511.3(A) Parking Garages. Parking garages used for parking or storage shall be unclassified.

511.7 Wiring and Equipment Installed Above Class I Locations. (A) Wiring in spaces above Class I locations shall be in metal raceways, PVC, RTRC, electrical nonmetallic tubing, flexible metal conduit, liquidtight flexible conduit, or Types MC, MI, or PLTC cable. (B) Equipment less than 12 feet above the floor level that may produce arcs, sparks, or particles of hot metal shall be of the totally enclosed type or constructed so as to prevent the escape of sparks or hot metal particles. Equipment such as lamps and lampholders installed above lanes through which vehicles are commonly driven or that may be exposed to physical damage shall be located not less than 3.7 m (12 ft) above floor level, unless of the totally enclosed type or otherwise protected.

511.12 Ground-Fault Circuit-Interrupter Protection for Personnel. All 125-volt, single-phase, 15- and 20-ampere receptacles installed in areas where electrical diagnostic equipment, electrical hand tools, or portable lighting equipment are to be used shall have GFCI protection for personnel.

511.16 Grounding and Bonding. All metal raceways, the metal armor or metallic sheath on cables, and all non-current-carrying metal parts of fixed and portable electrical equipment shall be bonded in accordance with 501.30(A) in Class I locations.

Article 513 — Aircraft Hangars

513.3 Classification of Locations.

• (A) Below Floor Level. Any pit or depression below the level of the hangar floor shall be classified as a Class I, Division 1 or Zone 1 location that extends up to said floor level.
• (B) Areas Not Cut Off or Ventilated. The entire area of the hangar, including any adjacent and communicating area not suitably cut off from the hangar, shall be classified as a Class I, Division 2 or Zone 2 location up to a level 18 inches (450 mm) above the floor.
• (C) Vicinity of Aircraft. The area within 1.5 m (5 ft) horizontally from aircraft power plants or aircraft fuel tanks shall be classified as a Class I, Division 2 or Zone 2 location that extends upward from the floor to a level 1.5 m (5 ft) above the upper surface of wings and of engine enclosures.
• (D) Areas Suitably Cut Off and Ventilated. Adjacent areas in which flammable liquids or vapors are not likely to be released, such as stock rooms and electrical control rooms, shall be unclassified where adequately ventilated and effectively cut off by walls or partitions.

513.7 Wiring and Equipment Not Installed in Class I Locations. (E) Lampholders of metal-shell, fiber-lined types shall not be used for fixed incandescent lighting. (F) Portable lighting equipment used inside aircraft or within a Class I location shall be identified for the location.

513.12 Ground-Fault Circuit-Interrupter Protection for Personnel. All 125-volt, single-phase, 15- and 20-ampere receptacles installed in areas where electrical diagnostic equipment, electrical hand tools, or portable lighting equipment are to be used shall have GFCI protection.

513.16 Grounding and Bonding applies 501.30(A) within Class I locations.

Article 514 — Motor Fuel Dispensing Facilities

514.3 Classification of Locations. Classified locations are as specified in Table 514.3(B)(1) for dispensing devices, and Table 514.3(B)(2) for compressed natural gas, liquefied natural gas, and liquefied petroleum gas dispensing.

Selected values from Table 514.3(B)(1) for a dispenser other than an overhead type:

514.8 Underground Wiring. Underground wiring shall be installed in threaded rigid metal conduit or threaded steel intermediate metal conduit. Any portion of electrical wiring that is below the surface of a Class I, Division 1 or Division 2 location shall be considered to be within a Class I, Division 1 location that shall extend at least to the point of emergence above grade.

Exception No. 1: Type MI cable shall be permitted where it is installed in accordance with Article 332.

Exception No. 2: Rigid nonmetallic conduit shall be permitted where buried under not less than 600 mm (2 ft) of cover. Where rigid nonmetallic conduit is used, threaded rigid metal conduit or threaded steel intermediate metal conduit shall be used for the last 600 mm (2 ft) of the underground run to emergence or to the point of connection to the aboveground raceway, and an equipment grounding conductor shall be included to provide electrical continuity of the raceway system and for grounding of non-current-carrying metal parts.

514.9 Sealing. (A) A listed seal shall be provided in each conduit run entering or leaving a dispenser or any cavity or enclosure in direct communication therewith. The sealing fitting shall be the first fitting after the conduit emerges from the earth or concrete. (B) Additional seals shall be provided in accordance with 501.15, and 501.15(B)(2) shall apply to horizontal as well as vertical boundaries of the defined Class I locations.

514.11 Circuit Disconnects.

• (A) General. Each circuit leading to or through dispensing equipment, including equipment for remote pumping systems, shall be provided with a clearly identified and readily accessible switch or other acceptable means, located remote from the dispensing devices, to disconnect simultaneously from the source of supply all conductors of the circuits, including the grounded conductor, if any.
• (B) Attended Self-Service Motor Fuel Dispensing Facilities. Emergency controls as specified in 514.11(A) shall be installed at a location acceptable to the authority having jurisdiction, but controls shall not be more than 30 m (100 ft) from dispensers.
• (C) Unattended Self-Service Motor Fuel Dispensing Facilities. Emergency controls as specified in 514.11(A) shall be installed at a location acceptable to the authority having jurisdiction, but the controls shall be more than 6 m (20 ft) but less than 30 m (100 ft) from the dispensers. Additional emergency controls shall be installed on each group of dispensers or the outdoor equipment used to control the dispensers.

The requirement that the disconnect open the grounded conductor as well is unusual in the Code and is a reliable exam item. It exists because leaving a neutral connected to a damaged dispenser can maintain an ignition source.

514.13 Maintenance and Service of Dispensing Equipment. Each dispensing device shall be provided with a means to remove all external voltage sources, including feedback, during periods of maintenance and service of the dispensing equipment.

514.16 Grounding and Bonding applies 501.30(A) in Class I locations.

Article 515 — Bulk Storage Plants

515.1 Scope. Article 515 covers a property or portion of a property where flammable liquids are received by tank vessel, pipelines, tank car, or tank vehicle and are stored or blended in bulk for the purpose of distributing such liquids by tank vessel, pipeline, tank car, tank vehicle, portable tank, or container.

515.3 and Table 515.3 classify the locations, including tank vehicle and tank car loading and unloading areas, the interior of tanks, and pits and sumps.

515.8 Underground Wiring parallels 514.8: threaded RMC or threaded steel IMC, with an exception for rigid nonmetallic conduit buried under not less than 2 feet of cover with the last 2 feet in threaded metal conduit and an equipment grounding conductor included.

515.16 Grounding and Bonding. All metal raceways, cable armor, and non-current-carrying metal parts shall be bonded per 501.30(A) in Class I locations.

Article 516 — Spray Application, Dipping, Coating, and Printing Processes Using Flammable or Combustible Materials

516.4 and Table 516.4 classify spray areas. In an open spray area the space within 5 feet (1.5 m) in all directions from the spray area is Class I or Class II, Division 1, and beyond that, extending 5 feet horizontally and upward to a height of 3 feet above the floor, is Division 2, subject to the specific configuration.

516.7 Wiring and Equipment Not Within Classified Locations. (A) Wiring above classified locations shall be in metal raceways, PVC, RTRC, or Type MI, MC, or TC cable. (B) Equipment that may produce arcs, sparks, or particles of hot metal, located above the classified location or above a location where readily ignitible residues may be deposited, shall be of the totally enclosed type or be so constructed as to prevent escape of sparks or hot metal particles.

516.10 Special Equipment covers spray application equipment, electrostatic equipment, and powder coating, with detailed requirements including minimum clearances between goods being coated and electrodes, and interlocks that de-energize the high-voltage supply when ventilation fails.