|NEC Article 511 - Commercial Garages, Repair and Storage
|By Mike Holt, for EC&M Magazine
Extracted from Mike Holt's "Understanding the 2002 NEC, Part 2"
Electric wiring and equipment installed in a Class I hazardous classified location shall be installed in accordance with the installation requirements contained in Chapters 1 through 4, as well as the requirements contained in Articles 500 and 501.
Article 511 applies to areas used for service and repair operations of self-propelled vehicles including passenger automobiles, buses, trucks, tractors, etc., in which volatile flammable liquids or gasses are used for fuel or power. Article 511 does not apply to residential garages or repair garages for watercraft, 4-wheelers or motorcycles.
Author's Comment: According to Article 100, a garage is a building or portion of a building in which one or more self-propelled vehicles shall be permitted to be kept for use, sale, storage, rental, repair, exhibition, or demonstration purposes.
(A) Unclassified Locations. Parking or storage 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 and the requirements of Article 511 are not applicable.
The storage, handling or dispensing into motor vehicles of alcohol-based windshield washer fluid in areas used for the service and repair operations of the vehicles shall not cause such areas to be classified as hazardous (classified) locations.
FPN No. 1: For further information, see NFPA 88A-1998, Standard for Parking Structures and NFPA 88B-1997, Standard for Repair Garages.
(B) Classified Locations. Classifications are done in accordance with Article 500. Areas used for motor fuel dispensers, or areas in which flammable fuel is transferred to vehicle fuel tanks, shall have the wiring installed in accordance with the requirements of Article 514.
Author's Comment: Some installations that could fall within the scope of Article 511 would include automobile service/repair centers, service/repair garage for commercial vehicles such as trucks and tractors, and service/repair garages for fleet vehicles such as cars, buses and trucks.
It is possible for an establishment to have a vehicle service/repair area that shall comply with Article 511, another area for fuel dispensing that shall comply with Article 514, with other areas such as show rooms, offices, or a parts department that shall comply with NEC chapters 1 through 4.
(1) Up to a Level of 18 in. Above the Floor. The service/repair area up to 18 in. above the floor shall be classified as Class I, Division 2. Figure 1 Note: Graphics not included in this newsletter.
Exception: If mechanical ventilation provides a minimum of four air changes per hour, the electrical AHJ can classify the area as nonclassified.
(2) Within 18 in. of the Ceiling. Where compressed natural gas (CNG) vehicles are repaired or stored, the area within 18 in. of the ceiling shall be classified as Class I, Division 2, except where ventilation of at least four air changes per hour is provided. [NFPA 88B, 3-1.1] Figure 2
(3) Any Pit of Depression Below Floor Level. Any pit or depression below the service/repair floor shall be considered a Class I, Division 1 location. Figure 3
Exception No. 1: If mechanical ventilation provides a minimum of six air changes per hour, the electrical AHJ can classify the area as a Class I, Division 2 location.
Exception No. 2: The area in a lubrication or service room without dispensing equipment shall be classified in accordance with Table 514.3(B)(1).
Author's Comment: An example of a location of a pit without fuel dispensing would be an oil change and lubrication service. Table 514.3(B)(1) under Lubrication or Service Room, Without Dispensing states that a pit is not classified.
(4) Classification of Adjacent Areas. Areas adjacent to classified locations such as stock rooms, switchboard rooms and other similar locations are not classified if mechanically ventilated at a rate of four or more air changes per hour or when the adjacent area is effectively cut off by walls or partitions. Figure 4
(5) Classification of Adjacent Areas by Special Permission. Areas adjacent to classified locations may be unclassified by the authority enforcing this Code for reason of ventilation, air pressure differentials or physical spacing.
511.4 Wiring and Equipment.
(A) Located in Class I Locations. Wiring and equipment within a Class I location (wiring methods, seals, etc.) shall be installed in accordance with the requirements of Article 501.
(1) Raceways. Threaded rigid metal or intermediate metal conduit shall be used. Raceways embedded in a masonry wall or buried beneath a floor are not considered to be within the Class I location unless the raceway enters the classified area. Figure 5
Exception: A raceway that enters a Class I, Division 1 or 2 location shall be threaded rigid or intermediate metal conduit, but rigid nonmetallic conduit (RNC) (with an equipment grounding conductor) shall be permitted to be used underground if it has at least 2 ft of cover. Figure 6
Author's Comment: If the raceway enters a classified location, the underfloor area takes on the classification of the above area, even if the conduit passes unbroken through the classified area, and terminates in an unclassified area. The concern is volatile gas seepage into the underfloor area through the conduit openings in the floor.
(B) Equipment Located in Class I Locations
(1) Fuel-Dispensing Units. Where fuel-dispensing units (other than liquid petroleum gas, which is prohibited) are located within buildings, the requirements of Article 514 shall govern.
(2) Portable Lighting Equipment. Portable lighting equipment shall have the lamp and its cord supported or arranged in such a manner that they shall not be installed in the locations classified in 511.3, or they shall be of a type approved for Class I, Division 1 locations.
511.7 Wiring and Equipment Above Class I Locations.
(A) Wiring in Spaces Above Class I Locations
(1) Fixed Wiring Methods. All wiring above a Class I location shall be within a raceway or MC, MI or PLTC in accordance with Article 725, or TC cable. Figure 7
(2) Pendants. In a Class I location, flexible hard usage cords shall be permitted to be used for pendants. See 400.4.
(B) Equipment Above Class I Locations.
(1) Fixed Electrical Equipment. Electrical equipment in a fixed position shall be located above the level of any defined Class I location or shall be identified for the location.
(a) Arcing Equipment. Equipment having make-and-break contacts installed less than 12 ft above the floor level (excluding receptacles, lamps and lampholders) shall be of the totally enclosed type or be of the type constructed to prevent sparks or hot metal particles from escaping.
(b) Fixed Lighting. Lampholders and lamps for fixed lighting over travel lanes or where exposed to physical damage shall be located not less than 12 ft above floor level, unless the luminaires are of the totally enclosed type or constructed to prevent sparks or hot metal particles from escaping.
Raceway, cable and boundary seals shall be installed in accordance with the requirements of 501.5 and 501.5(B)(2).
Author's Comment No. 1: Where the Class 1, Division 1 boundary is beneath the ground, the sealing fitting shall be permitted to be installed after the conduit leaves the ground. There shall be no union, coupling, box or fitting between the conduit seal and the point where the conduit leaves the ground [501.5(A)(4) Exception 2]. Figure 8
511.10 Special Equipment
(A) Battery Charging Equipment. Battery chargers and batteries being charged shall not be located within a Class I, Division 1 or 2 area as classified in 511.3.
(B) Electric Vehicle Charging.
(1) General. Electrical conductors and equipment that connect an electric automotive-type vehicle shall be installed in accordance with the requirements contained in Article 695. Figure 9
511.12 GFCI Protection.
GFCI protection to protect personnel shall be required for all 125V single-phase 15A and 20A receptacles used for service and repair operations such as electrical automotive diagnostic equipment, electrical hand-tools, portable lighting devices, etc. Figure 10