Conduit, Wireway, and Cable Tray

Choose the best answer:

  1. You must support exposed vertical risers for industrial machinery or fixed equipment at intervals not exceeding _____ ft, when the IMC or RMC conduit is made up with threaded couplings, firmly supported at the top and bottom of the riser, and no other means of support is available.
    (a) 6
    (b) 10
    (c) 15
    (d) 20

  2. You may not use threadless couplings or connectors on threaded IMC or RMC ends unless the fittings are listed for that purpose.
    (a) true
    (b) false

  3. If a building is equipped with a fire sprinkler system, installed in accordance with NFPA 13-1999, you can install ENT exposed or concealed in buildings of any height.
    (a) true
    (b) false

  4. Where insulated conductors ___ AWG or larger are pulled through a wireway, the distance between raceway and cable entries enclosing the same conductor may not be less than required by 314.28.
    (a) 10
    (b) 8
    (c) 6
    (d) 4

  5. You can use cable trays as a support system for _____.
    (a) services, feeders, and branch circuits
    (b) communications circuits
    (c) control and signaling circuits
    (d) all of these

  6. When in cable trays and where exposed to direct sunlight, insulated conductors and jacketed cables must be _____ as sunlight resistant.
    (a) listed
    (b) approved
    (c) identified
    (d) a and b

  7. You can use nonmetallic cable trays in corrosive areas and in areas requiring voltage isolation.
    (a) true
    (b) false

  8. You must provide supports for cable trays in accordance with _____.
    (a) installation instructions
    (b) NEC rules
    (c) a and b
    (d) none of these

  9. In industrial facilities where conditions of maintenance and supervision ensure only qualified persons will service the installation, you may use cable tray systems to support _____.
    (a) raceways
    (b) cables
    (c) boxes and conduit bodies
    (d) all of these

Answers and Discussion

  1. d, 20. Wording was added to 342.30(B)(3) and 344.30(B)(3) to expand the use of vertical risers to other equipment that is fixed in place. The change also clarifies that you can use vertical risers of IMC and RMC for fixed equipment in any occupancy, not just industrial machinery in an industrial facility.

  2. a, true. A new sentence in 342.42 and 344.42 prohibits the use of threadless fittings on threaded ends of IMC and RMC, respectively, because the taper of the threads could affect the impedance of the effective fault current path.

  3. a, true. A new Exception to rule 362.10(2) permits you to install ENT exposed or concealed in a building if it's equipped with a fire sprinkler system installed in accordance with NFPA 13-1999.

  4. d, 4. Sec. 376.23 was revised to clarify that when a wireway is used as a pullbox with conductors 4 AWG and larger, it must be sized as a pullbox in accordance with the rules of 314.28.

  5. d, all of these. New text in 392.3 clarifies you can use cable trays for the support of power, lighting, signaling, and communications circuits.

  6. c, identified. A new sentence in 392.3 specifies that where exposed to the sun, conductors and cables must be identified as suitable for the intended purpose.

  7. a, true. The revised text in 392.3(E) clarifies you can use nonmetallic cable tray for purposes other than corrosive areas or voltage isolation.

  8. a, installation instructions. New wording in 392.6(C) requires you to install cable tray per installation instructions. The '99 NEC didn't specify cable tray support.

  9. d, all of these. Revised text in 392.6(J) clarifies that in industrial facilities where conditions of maintenance and supervision ensure only qualified persons service the installation, and where the cable tray systems are designed and installed to support the load, you can attach any size box, as well as conduit bodies, to the bottom or side of a cable tray system.

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

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