392.3.Uses Permitted. (B) In Industrial Establishments. (1) Single Conductor.
Section 392.3(B)(1) covers 600 volt and Type MV single conductor cables.
There are several sections which cover the requirements for the use of single conductor cables in cable tray even though they only comprise a small percentage of cable tray wiring systems. Such installations are limited to qualifying industrial facilities [See Section 392.3(B)]. Many of the facility engineers prefer to use three conductor power cables. Normally, three conductor power cables provide more desirable electrical wiring systems than single conductor power cables in cable tray (See
Section 392.8. Cable installation - three conductor vs. single conductor cables).
392.3(B)(1)(a)
Single conductor cable shall be No. 1/0 or larger and shall be of a type listed and marked on the surface for use in cable trays. Where Nos. 1/0 through 4/0 single conductor cables are used, the maximum allowable rung spacing for ladder cable tray is 9 inches.
392.3(B)(1)(b)
Welding cables shall comply with Article 630, Part IV which states that the cable tray must provide support at intervals not to exceed 6 inches. A permanent sign must be attached to the cable tray at intervals not to exceed 20 feet. The sign must read “CABLE TRAY FOR WELDING CABLES ONLY”.
392.3(B)(1)(c)
This section states that single conductors used as equipment grounding conductors (EGCs) in cable trays shall be No. 4 or larger insulated, covered or bare.
The use of a single conductor in a cable tray as the EGC is an engineering design option. Section 300.3(B) states that all conductors of the same circuit and the EGC, if used, must be contained within the same cable tray.
The other options are to use multiconductor cables that each contain their own EGC or to use the cable tray itself as the EGC in qualifying installations [see Section 392.3(C)]
If an aluminum cable tray is installed in a moist environment where the moisture may contain materials that can serve as an electrolyte, a bare
Cable Tray Manual
copper EGC should not be used. Under such conditions, electrolytic corrosion of the aluminum may occur. For such installations, it is desirable to use a low cost 600 volt insulated conductor and remove the insulation where connections to equipment or to equipment grounding conductors are made.
information on single conductors used as the EGC for cable tray systems).
392.3.Uses Permitted. (B) In Industrial Establishment (2) Medium Voltage.
Single and multiconductor type MV cables (Article
328)must be sunlight resistant if exposed to direct sunlight. Single conductors shall be installed in accordance with 392.3(B)(1)
392.3.Uses Permitted. (C) Equipment Grounding Conductors.
Cable tray may be used as the EGC in any installation where qualified persons will service the installed cable tray system. There is no restriction as to where the cable tray system is installed. The metal in cable trays may be used as the EGC as per the limitations of table 392.7(B)(2). See Section
392.7.Grounding in this manual for additional information on the use of cable trays as the EGC.
392.3.Uses Permitted. (D) Hazardous (Classified) Locations.
This section states that if cable tray wiring systems are installed in hazardous (classified) areas, the cables that they support must be suitable for installation in those hazardous (classified) areas. The cable carries the installation restriction. The installation restriction is not on the cable tray except that the cable tray installations must comply with Section 392.4. The following is an explanation of the parts of the code which affect the use of cable tray in hazardous locations.
501.4.Wiring Methods - Listed Termination Fittings. (A) Class I, Division 1 (Gases or Vapors).
Cooper B-Line, Inc
15