Quizzes on the Code

Mike Holt answers EC&M readers' questions on the National Electrical Code.

Choose the best answer:

  1. The requirements in Art. 511 apply to locations intended for service and repair operations in connection with self-propelled vehicles like ____, in which volatile flammable liquids or flammable gases are used for fuel or power.
    (a) buses
    (b) trucks
    (c) tractors
    (d) all of these

  2. You must follow the requirements of Art. 514 when installing the wiring in areas used for motor fuel dispensers or areas in which flammable fuel is transferred to vehicle fuel tanks.
    (a) true
    (b) false

  3. The service and repair area up to ___ in. above the floor shall be classified as Class I, Division 2.
    (a) 6
    (b) 12
    (c) 18
    (d) 24

  4. The area within ___ in. of the ceiling in locations where compressed natural gas (CNG) vehicles are repaired or stored must be classified as Class I, Division 2, except where ventilation of at least four air changes per hour is provided.
    (a) 6
    (b) 12
    (c) 18
    (d) 24

  5. Any pit or depression below the service and repair floor shall be considered a Class I, Division 1 location.
    (a) true
    (b) false

  6. If you're installing wiring or equipment within a Class I location, you must run the wires in threaded rigid metal or intermediate metal conduit. But if the installation requires you to run the wiring underground, you can use rigid nonmetallic conduit (RNC) with an equipment grounding conductor if it has at least ___ ft of cover.
    (a) 1
    (b) 2
    (c) 3
    (d) none of these

  7. Lampholders and lamps for fixed lighting over travel lanes or where exposed to physical damage must be more than 12 ft above floor level, unless the luminaires are completely enclosed or are constructed to prevent sparks or hot metal particles from escaping.
    (a) true
    (b) false

  8. The NEC requires GFCI protection for all 125V single-phase 15A and 20A receptacles used for service and repair operations like electrical automotive diagnostic equipment, electrical hand-tools, and portable lighting devices.
    (a) true
    (b) false

Answers and Discussion

  1. (d), all of these

    Although Art. 511 covers service and repair garages for these vehicles, it doesn't apply to residential garages or repair shops for watercraft, 4-wheelers, or motorcycles.

  2. (a), true

    It's possible for an establishment to have a vehicle service and repair area that must comply with Art. 511, another area for fuel dispensing that must comply with Art. 514, and other areas, such as show rooms, offices, or a parts department, that must comply with Chapters 1 through 4.

  3. (c), 18.

    The only exception to 511.3(B)1 is when the enforcing agency determines that mechanical ventilation is providing a minimum of four air changes per hour or 1 cu ft per min of exchanged air for each square foot of floor area. The ventilation system must provide for air exchange across the entire floor area within 12 in. of the floor.

  4. (c), 18

    Per 511.3(B)(2).

  5. (a), true

    There are two exceptions to 511.3(B)(3). The first states, “any pit or depression in which six air changes per hour are exhausted at the floor level of the pit shall be permitted to be judged by the enforcing agency to be a Class I, Division 2 location.” The second states, “lubrication and service rooms without dispensing shall be classified in accordance with Table 514.3(B)(1).”

  6. (b), 2

    An Exception to 511.4(A)(1) for RNC stipulates that 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.

  7. (a), true

    Per 511.7(B)(1)(b).

  8. (a), true

    Per 511.12.

Are you still confused by the Code? For additional information on Code-related topics please visit www.mikeholt.com or send an e-mail directly to the author at [email protected].

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.