|The following are the changes in the 2002 National Electrical Code that affect cable tray installations. Most of these changes to the cable tray section were proposed and promoted by the Cable Tray Institute to further the applicability of cable trays.|
|The National Electrical Code is one of many National Fire Protection standards that are available from:
The National Fire Protection Association
4 Battery March Park
PO BOX 9101
Quincy, MA 02269 – 9101
Tel No 1-800-344-3555
Note: The CTI is a strong participant in the NEC code process. This cycle the CTI submitted 19 code proposals and 5 public comments.
Renumbering of Code Articles
The NEC task group on usability renumbered the cable tray article 318 and other cable articles that are used in cable trays:
|1999 NEC||2002 NEC|
|Powered Control Tray Cable||340||336|
|Metal Clad Cable||334||330|
|Medium Voltage Cable||326||328|
NEMA Cable Trays Standards
As a result of CTI proposals, NEMA Cable Tray Standards have been added to article 318 (392) as a fine print note to section 318 (392) –I. The wording will be:
“For further information on cable trays, see NEMA-VE 1, 1998 Metal Cable Tray
Systems; NEMA-VE 2, 1996, Metal Cable Tray Installation Guidelines; and
NEMA-FG 1, 1998, Nonmetallic Cable Tray Systems.”
This is a very significant change. As indicated in the CTI proposals, these standards are an industry resource in the application, selection, and installation of cable trays both metallic and nonmetallic.
Single Conductor Cables in Solid Bottom Cable Trays
Section 318-3(b) was revised to permit, in industrial establishments only where conditions of maintenance and supervision ensure that only qualified persons will service the installed cable tray system, solid bottom cable trays were added to ladder, ventilated channel, etc., as the types of cable trays allowing single conductor cables, welding cables, single conductor, equipment grounding conductors, and type MV cables, to be installed.
Fill requirements for single conductors cables in solid bottom cable trays were proposed by the CTI but not accepted. CTI will discuss these requirements and ampacity ratings in the next Cable Gram. Note: Do not use 318-11(b) for ampacity for single conductor cables in solid bottom cable trays. Take the conservative approach. Use tables 310-16 and 310-18.
Solid Bottom Channel Cable Trays
Solid bottom channel cable trays were added in new section 318-9(f) and table 318-9(e). Table 318-9(e) will include two inch width cable channel, solid and ventilated channel, and 2,3,4, and 6 inch wide channel. Table 318-9(e) covers allowable cable fill areas. Two-inch width for ventilated channel was also added to this table.
Other Changes to Article 318
|318-3||New requirement that where cables in tray are exposed to the direct rays of the sun, they shall be identified as sunlight resistant for all occupancies, not just industrial.|
|318-3||New wording – Cable tray shall be permitted to be used as a support system for services, feeders, branch circuits, control circuits, and signaling circuits. This change explicitly permits cable trays for cable systems for all types of circuits.|
|381-3(a)||Optical Fiber Raceways were added as permitted wiring methods.|
|318-3(d)||A proposal was accepted to explicitly permit cables in hazardous areas classified by the international zone system, if the cables comply with the cable requirements for zone locations.|
|318-3(e)||New wording indicating that non metallic cable tray is permitted for purposes other than voltage isolation or corrosive area application.|
|318-5(g)new||A new section will be added to indicate that cable trays and associated fittings shall be identified for the intended use.|
|318-6(a)||An editorial change was submitted to clarify that cable transitions for individual conductor as open wiring are permitted from one cable tray to another, and from cable tray to raceway, and from cable tray to equipment.|
|318-6(j)||Raceway’s, Cables, and Outlet Boxes Supported from Cable Trays. This section was significantly reworded. The term “Conduit bodies” replaced the words “outlet boxes.” After the words “supported the load,” “such systems shall be permitted to support raceways, cables, boxes, and conduit bodies covered in 370-1” replaced the existing wording. At the end of the first paragraph after “shall be used” the following wording replaced the existing words.“to securely fasten the raceway to the cable tray system. Additional supporting and securing of the raceway shall be in accordance with the requirements of the appropriate raceway article.
The last paragraph has been replaced with the following:
“For boxes and conduit bodies attached to the bottom or side of a cable tray system, fastening and supporting shall be in accordance with the requirements of 370-23.”
|Article 800 Change|
|800-52(d)||Section 800-52(d) was changed to add the following at the end of this section. Communication Raceways, as described in 800-51 shall be permitted to be installed in cable trays. Note: These raceways include Plenum, Riser and General-Purpose raceways, listed as having the proper fire-resistant characteristics.|