Boxes and Cable

Choose the best answer:

  1. The Code requires you to mount an extension ring over a flush box when installing a surface extension on a flush-mounted box.
    (a) true
    (b) false

  2. A ______ mounted luminaire weighing no more than 6 lb may be supported by device boxes or plaster rings that are secured to other boxes, provided the luminaire is secured to the box with no less than two No. 6 or larger screws.
    (a) ceiling
    (b) wall
    (c) a or b
    (d) none of these

  3. Outlet boxes may be used to support luminaires that weigh as much as ___ lb.
    (a) 35
    (b) 50
    (c) 75
    (d) 100

  4. Ceiling fans weighing no more than ___ lb may be supported by an outlet box identified for this purpose.
    (a) 35
    (b) 50
    (c) 75
    (d) 100

  5. AC cable installed through or parallel to framing members needs not be protected from penetration by screws or nails.
    (a) true
    (b) false

  6. NM cable must be ______.
    (a) marked
    (b) approved
    (c) identified
    (d) listed

  7. You may install nonmetallic-sheathed cable in multifamily buildings of Types III, IV, and V construction above three stories, except as prohibited in 334.12.
    (a) true
    (b) false

  8. You may install NM cable as an open run in dropped or suspended ceilings in other than one- and two-family and multifamily dwellings.
    (a) true
    (b) false

  9. You must size Type SE service-entrance cable used for interior wiring based on the 60°C conductor ampacity limitations listed in 334.80.
    (a) true
    (b) false

Answers and Discussion

  1. (a), true. A change to 314.22 clarifies the requirements for the installation of exposed surface extensions. You're now required to mount and mechanically secure an extension ring over the flush box when installing a surface extension on a flush-mounted box.

  2. (b), wall. An exception to 314.27(A) was revised to clarify that wall-mounted fixtures may be supported by device boxes or device plaster rings with no fewer than two No. 6 or larger screws.

  3. (b), 50. Per 314.27(B), outlet boxes may be used to support luminaires that weigh as much as 50 lb. Luminaires that weigh more than 50 lb must be supported independent of the outlet box, unless the box is listed for the luminaire's weight.

  4. (a), 35. Where a box is used as the sole support for a ceiling paddle fan, the box must be listed for this purpose and be able to support the weight of the fan. Typically, an outlet box identified for this purpose may be used to support only ceiling paddle fans that weigh as much as 35 lb [314.27(D) and 422.18(A)]. Ceiling paddle fans exceeding 35 lb must be supported independent of the outlet box, unless the box is listed to support the weight of the ceiling fan.

  5. (b), false. Despite its protective element, AC cable installed through or parallel to framing members must be protected against penetration by screws or nails per 300.4 and 320.17. The nearest outside surface of the cable must be located no less than 1.25 in. from the nearest edge of the framing member or protected by a suitable metal plate.

  6. (d), listed. A new section (334.6) requires NM cable to be listed. This requirement will ensure that imported NM cable meets U.S. expectations relative to electrical and fire characteristics.

  7. (a), true. Subsection 334.10(2) now allows you to install nonmetallic-sheathed cable — as covered by Art. 334 — in buildings above three stories. The number of floors varies according to the specific construction type, fire resistance rating, and nature of the occupancy, as well as the presence of other fire protection features like automatic sprinklers.

  8. (b), false. New text was added to 334.12(A)(1), prohibiting the installation of NM cables as open runs in suspended ceilings of commercial occupancies.

  9. (b), false. Sec. 338.10(B)(4)(1) clarifies that when SE cable is used for interior wiring, it must comply with the installation requirements of Parts I & II for NM cable, but not the 60°C conductor ampacity limitations of 334.80.

Questions and answers excerpted from Mike Holt's Illustrated Changes to the NEC, 2002 Edition.

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 mike@mikeholt.com.