Cooper Bussmann CT02MAN - Manual (Page 17)

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
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.
(See Section 392.7. Grounding, for additional
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).
501-4(A)(1)(b) Type MI cable may be installed in
cable tray in this type of hazardous (classified) area.
501-4(A)(1)(c) allows Type MC-HL cables to be
installed in Class I, Division I areas if they have a
gas/vapor tight continuous corrugated aluminum
sheath with a suitable plastic jacket over the sheath.
They must also contain equipment grounding
conductors sized as per Section 250.122 and listed
termination fittings must be used where the cables
enter equipment.
15
Cable Tray Manual Cooper B-Line, Inc