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CT02MAN
2002
CABLE TRAY MANUAL
Based on the
®
2002 National Electrical Code
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Table of Contents Page No. Introduction ...................................................................................................................... 2 Why Cable Tray? Safety .................................................................................................................... 3 Dependability ........................................................................................................... 4 Space Savings ..........................................................
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INTRODUCTION The B-Line Cable Tray Manual was produced by B-Line's technical staff. B-Line has recognized the need for a complete cable tray reference source for electrical engineers and designers. The ® following pages address the 2002 National Electric Code requirements for cable tray systems as well as design solutions from practical experience. The information has been organized for use as a reference guide for both those unfamiliar and those experienced with cable tray. Nearly every aspect
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WHY CABLE TRAY? BECAUSE A CABLE TRAY WIRING SYSTEM PROVIDES SAFE AND DEPENDABLE WAYS TO SAVE NOW AND LATER Large numbers of electrical engineers have CABLE TRAY SAFETY FEATURES limited detail knowledge concerning wiring systems. A properly engineered and installed cable tray There is the tendency by engineers to avoid wiring system provides some highly desirable safety becoming involved in the details of wiring systems, features that are not obtainable with a conduit wiring leaving the wiring sy
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CABLE TRAY DEPENDABILITY CABLE TRAY SPACE SAVINGS A properly designed and installed cable tray When compared to a conduit wiring system, an system with the appropriate cable types will provide equivalent cable tray wiring system installation a wiring system of outstanding dependability for the requires substantially less space. control, communication, data handling, instrumentation, and power systems. The Increasing the size of a structure or a support dependability of cable tray wiring systems
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CABLE TRAY WIRING SYSTEM monitored. For an equal capacity wiring system, only a few cable tray runs would have to be COST SAVINGS monitored. Usually, the initial capital cost is the major factor • Dedicated cable tray installation zones alert in selecting a project's wiring system when an other engineering disciplines to avoid designs that evaluation is made comparing cable tray wiring will produce equipment and material installation systems and conduit wiring systems. Such an conflicts in these
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COST - Cable Tray vs. Conduit (Equivalent Conductor Fill Areas) 16000 Material Cost 14000 Labor Cost @ $25/hr per NECA labor units. 12000 10000 Total Installed 8000 Cost ($) 6000 4000 2000 0 Ladder Solid Bottom EMT Rigid Steel Cable Tray Cable Tray Conduit 1 2 3 4 Installation: 200 linear feet of cable supported with four 90° direction changes and all trapeze supports on 8 ft. spans. 1. Hot dip galvanized steel, 18" wide, ladder cable tray (9" rung spacing) with all hardware. 2. Hot dip galvani
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• The higher the elevation of the wiring system, to be made on a weekend or on a holiday at the more important the number of components premium labor costs to avoid shutting down required to complete the installation. Many production or data processing operations during additional man-hours will be required just moving normal working hours. the components needed for the conduit system up • Conductor insulation damage is common in to the work location. conduits since jamming can occur when pullin
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• Moisture is a major cause of electrical IN MOST CASES AN OBJECTIVE equipment and material failures. Breathing due to EVALUATION OF THE REQUIREMENTS temperature cycling results in the conduits FOR MOST HIGH DENSITY WIRING accumulating relatively large amounts of moisture. SYSTEMS WILL SHOW THAT A CABLE The conduits then pipe this moisture into the TRAY WIRING SYSTEM PROVIDES A electrical equipment enclosures which over a period WIRING SYSTEM SUPERIOR TO A of time results in the deterioration of
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® AN IN-DEPTH LOOK AT 2002 NEC ARTICLE 392 - CABLE TRAY ® (The following code explanations are to be used with a copy of the 2002 NEC .) ® To obtain a copy of the NEC contact: ® National Fire Protection Association 1 Batterymarch Park • P.O. Box 9101 Quincy, Massachusetts 02269-9101 1-800-344-3555 overall strength of the cable tray. Specifiers should 392.1. Scope. be aware that some cable tray manufacturers do not account for this load reduction in their published cable tray load charts. B-
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Channel cable tray systems (B-Line's cable channel) are available in 3, 4, and 6 inch widths ® with ventilated or solid bottoms. The 2002 NEC now recognizes solid bottom cable channel. ® Prior to the 2002 Code, the NEC did not have any specific provisions for the use of solid cable channel. Steel Ventilated Trough Instead of large conduits, cable channel may be ® The 1999 NEC added the word ‘ventilated’ in used very effectively to support cable drops from the front of trough to clear up some con
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The words "and other similar structures." were In an indoor industrial installation 10 or 12 foot incorporated in Section 392.1 for future types of tray sections may be easier to handle and install as cable tray that might be developed, such as center you may have piping or ducting to maneuver supported type cable tray. All the technical around. However, using 20 foot instead of 12 foot ® information developed by the 1973 NEC straight sections may provide labor savings during Technical Subcommit
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® Cable Tray Materials The 2002 NEC also added a new requirement that where cables in tray are exposed to the direct Metallic cable trays are readily available in aluminum, rays of the sun, they shall be identified as sunlight pregalvanized steel, hot-dip galvanized after resistant for all occupancies, not just industrial. fabrication, and stainless steel. Aluminum cable tray should be used for most installations unless specific 392.3. Uses Permitted. (A) Wiring corrosion problems prohibit it
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® on the use of Type MI cable is that it may not be 1975 NEC (as an item associated with the revision used where it is exposed to destructive corrosive of Article 318-Cable Trays). Type TC cable is a conditions unless protected by materials suitable for multiconductor cable with a flame retardant the conditions. Type MI cable without overall nonmetallic sheath that is used for power, lighting, nonmetallic coverings may be installed in ducts or control, and signal circuits. It is the most common
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instrumentation and data handling systems. These containing Type PLTC cables will be exposed to any are very critical circuits that impact on facility safety significant amount of hot metal splatter from and on product quality. Type ITC cable must be welding or the torch cutting of metal during supported and secured at intervals not exceeding 6 construction or maintenance activities, temporary feet [See Section 727.4]. metal or plywood covers should be installed on the cable tray to prevent cabl
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392.3. Uses Permitted. (B) In Industrial copper EGC should not be used. Under such conditions, electrolytic corrosion of the aluminum Establishments. (1) Single Conductor. may occur. For such installations, it is desirable to Section 392.3(B)(1) covers 600 volt and Type MV use a low cost 600 volt insulated conductor and single conductor cables. remove the insulation where connections to equipment or to equipment grounding conductors There are several sections which cover the are made. (See Sect
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501-4(A)(1)(d) allows Type ITC-HL cable to be This is an extremely important exception stating installed in Class I, Division I areas if they have a that cable seals are not required when a cable goes gas/vapor tight continuous corrugated aluminum from an unclassified area through a classified area sheath with a suitable plastic jacket over the sheath then back to an unclassified area. and provided with termination fittings listed for the application. 501.5. Sealing and Drainage. (E) Cable Seals
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Note 1. The cables are limited to a single layer in ordinary locations. with spacing between cables equal to the diameter 503.3. Wiring Methods. (A) Class III, Division 1 of the largest adjacent cable. This means that the and (B) Class III, Division 2 (Ignitable Fibers or cables must be tied down at frequent intervals in Flyings). Type MI or MC cables may be installed in horizontal as well as vertical cable trays to maintain cable tray in these types of hazardous (classified) the cable spacing.
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high amperage short circuit if a low resistance not so. Only the appropriate multiconductor cable metallic path (metallic cable tray or metallic raceway) types as per Section 392.3(A) may be installed in is present [See information under Section 392.5(F) solid bottom cable trays. Nonmetallic Cable Trays]. Cable tray may be used to support data process wiring systems in air handling areas below raised 392.4. Uses Not Permitted. floors as per Sections 300.22(D) and 800.52(D). ® This is the only
