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The NEC changes to account for new fuels
There were many changes in the 2002 National Electrical Code. Some were major changes of great consequence and others were simply renumbering of existing articles and sections or consisted of subtle changes. Changing the title of Article 514 from Gasoline Dispensing and Service Stations to Motor Fuel Dispensing Facilities is not subtle, but on the surface does not appear to be a change of major consequence. That could not be further from the truth.
Our lives have changed dramatically in many ways in the past 20 years, the least of which seems to be in the way we fuel and service our vehicles. For most of our lives, we took our cars, trucks, motorcycles and other vehicles down to the gas station for gasoline and oil. We had our vehicles lubed and the oil changed and other repairs done in the service bays of the gasoline station.
Then came the self-service gas station with connected convenience stores, often located in former service station bays; and the vehicle lubritorium facilities, where a vehicle could have its oil changed and a lube job in 15 minutes. Along with these other changes, the price of oil and gasoline started to increase, causing a search for alternative fuels. Diesel-, compressed natural gas-, liquefied natural gas-, and liquefied petroleum gas-powered cars and trucks became more common and are now viable options for many consumers.
With these changes in fuel and the subsequent changes in servicing of vehicles, a major change in Article 514 was necessary to address the various fuels handled or stored at these facilities. The first order of business was to rename Article 514 and the function of these facilities as “motor fuel dispensing facilities” and to change the scope of the article to address these changes. The second was to provide a definition for “motor fuel dispensing facilities.” The third was to change the classified and unclassified locations around and within the facilities to reflect the types of fuels dispensed and contained within the vehicles.
The scope in Article 514 was changed to state that motor fuel dispensing occupancies are locations where gasoline, other volatile flammable liquids, or liquefied flammable gases are transferred to the fuel tanks or auxiliary fuel tanks of self-propelled vehicles, or to approved containers. This matches the change in the title.
This article covers the dispensing of flammable liquids and gases but not combustible liquids and gases. A flammable liquid is a liquid designated as a Class I liquid that has a flash point of 100 F (37.8 C) and having a vapor pressure not exceeding 40 psia at 100 F (37.8 C). Flash point is the minimum temperature at which a liquid gives off vapor in sufficient concentration to form an ignitable mixture with air, near the surface of the liquid, as specified by test. Gasoline is a Class I liquid since its flash point is -46 C and thus is considered to be a flammable liquid.
A combustible liquid is one having a flash point at or above 100 F (37.8 C) and is subdivided into Class II liquids and Class III liquids. Numbers 1, 2 and 4 diesel fuels have flash points at or above 100 F, clearly placing them into the combustible liquids group. These fuels are commonly dispensed in a “gas station” but the scope of Article 514 limits the coverage to flammable liquids or gases only so compliance to Article 514 for combustible liquids, such as diesel fuel, is not necessary. Additives can be added or vapor pressures increased, changing these liquids from combustible to flammable and, thus, changing the classification.
If the diesel dispenser is located within 20 feet of a gasoline dispenser, the area surrounding the diesel dispenser is within the Class I, Division 2 area. If a depression exists under the diesel dispenser where a gasoline dispenser is located within 20 feet, the depression under the diesel dispenser would be Class I, Division 1.
Since compressed natural gas (CNG), liquefied natural gas (LNG), and liquefied petroleum gas (LPG) may be handled, dispensed or stored in motor fuel dispensing facilities, Section 514.3(B)(2) requires compliance with a new Table 514.3(B)(2). This new table is used to delineate and classify areas for these gases. Check this table out before installing a dispenser for these materials.
Where compressed natural gas or liquefied natural gas dispensers are located beneath a canopy or enclosure, either the canopy or enclosure must be designed to prevent accumulation or entrapment of ignitable vapors or all electrical equipment installed beneath the canopy must be suitable for Class I, Division 2 hazardous (classified) locations.
So, as our world changes, the NEC must change along with it. EC
ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at [email protected].