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November 29, 2018 <br /> The hazardous classified area boundaries are also affected by the use of open <br /> containers in the hangar and the potential for aircraft to be previously fueled. The open <br /> container and fueled aircraft requirements are based on current (2017) National <br /> Electrical Code (NEC) prescriptive requirements. When hazardous area boundaries for <br /> these three requirements are overlaid, each condition contributes to part of the <br /> boundary definition. Unfortunately this generates a relatively complicated boundary that <br /> will be difficult for inspectors, designers, and electricians to visualize. For this reason, <br /> the boundaries have been simplified in a conservative manner—the net effect of these <br /> decisions is shown in the Boeing drawings submitted with this letter. <br /> Technical Recommendations <br /> The technical recommendation is comprised of three elements: Fueled aircraft, open <br /> containers, and paint application. How each elements boundaries were determined, <br /> and how it contributes to the overall boundary definition is described as follows: <br /> Fueled aircraft <br /> The requirements for fueled aircraft are drawn from the 2017 NEC section 513.3 <br /> which states: <br /> 513.3 Classification of Locations. <br /> (A)Below Floor Level.Any pit or depression below the level of the hangar floor shall be <br /> classified as a Class I, Division 1 or Zone 1 location that shall extend up to said floor <br /> level. <br /> (B)Areas Not Cut Off or Ventilated.The entire area of the hangar, including any <br /> adjacent and communicating areas not suitably cut off from the hangar, shall be <br /> classified as a Class I, Division 2 or Zone 2 location up to a level 450 mm (18 in.) above <br /> the floor. <br /> (C)Vicinity of Aircraft. <br /> (1)Aircraft Maintenance and Storage Hangars.The area within 1.5 m (5 ft) horizontally <br /> from aircraft power plants or aircraft fuel tanks shall be classified as a Class I, Division 2 <br /> or Zone 2 location that shall extend upward from the floor to a level 1.5 m (5 ft) above <br /> the upper surface of wings and of engine enclosures. <br /> The basement below the aircraft is currently and will remain a Class I Division 1 <br /> location. <br /> The entire area of the hangar not suitably cut off from the hangar, is currently and <br /> will remain a Class I Division 2 location up to a level 18 inches above the floor. <br /> The requirements defined in section 513.3.C.1 will be exceeded by those <br /> required by open containers and paint application, and therefore do not affect the <br /> hazardous area boundaries. <br /> age�u2 0 <br />