Cooper Bussmann CT02MAN - Manual (Page 15)

on the use of Type MI cable is that it may not be
used where it is exposed to destructive corrosive
conditions unless protected by materials suitable for
the conditions. Type MI cable without overall
nonmetallic coverings may be installed in ducts or
plenums used for environmental air and in other
space used for environmental air in accordance with
Sections 300.22(B) and (C). Cable tray may be
installed as a support for Type MI cable in any
location except where the cable is installed in a
hoistway. Section 332-30 states that MI cable shall
be securely supported at intervals not exceeding 6
feet (1.83 m). Type MI cable has a UL two hour fire
resistive rating when properly installed. An
installation requirement for this rating is that the
cable be securely supported every 3 feet. Steel or
stainless steel cable trays should be used to support
Type MI cable being used for critical circuit service.
During severe fire conditions, steel or stainless steel
cable tray will remain intact and provide support
longer than aluminum or fiberglass reinforced plastic
cable trays.
Type MC Cable: Metal-clad cable (Article 330).
There are large amounts of Type MC cable installed
in industrial plant cable tray systems. This cable is
often used for feeder and branch circuit service and
provides excellent service when it is properly
installed. The metallic sheath may be interlocking
metal tape or it may be a smooth or corrugated
metal tube. A nonmetallic jacket is often extruded
over the aluminum or steel sheath as a corrosion
protection measure. Regular MC cable, without
nonmetallic sheath, may be supported by cable tray
in any hazardous (classified) area except Class I and
Class II, Division 1 areas. For Type MC cables to
qualify for installation in Class I and Class II Division
I areas (Section 501-4(A) (1) (c&d), they must have a
gas/vapor tight continuous corrugated aluminum
sheath with a suitable plastic jacket over the sheath.
They must also contain equipment grounding
conductors and listed termination fittings must be
used where the cables enter equipment. Type MC
Cable employing an impervious metal sheath
without overall nonmetallic coverings may be
installed in ducts or plenums used for environmental
air in accordance with Section 300.22(B) and may
be installed in other space used for environmental
air in accordance with Section 300.22(C). The
maximum support spacing is 6 feet (1.83 m).
Type TC Cable: Power and control tray cable
(Article 336). This cable type was added to the
1975 NEC ® (as an item associated with the revision
of Article 318-Cable Trays). Type TC cable is a
multiconductor cable with a flame retardant
nonmetallic sheath that is used for power, lighting,
control, and signal circuits. It is the most common
cable type installed in cable tray for 480 volt
feeders, 480 volt branch circuits, and control
circuits. Where Type TC cables comply with the
crush and impact requirements of Type MC cable
and is identified for such use, they are permitted as
open wiring between a cable tray and the utilization
equipment or device. In these instances where the
cable exits the tray, the cable must be supported and
secured at intervals not exceeding 6 feet (See
Section 336.10(6)). The service record of UL listed
Type TC cable where properly applied and installed
has been excellent.
For those installations where the NEC ® allows its
use, a cost savings is realized by using Type TC
cables instead of Type MC cables. Type TC cable
may be installed in cable tray in hazardous
(classified) industrial plant areas as permitted in
Articles 392, 501, 502, 504 and 505 provided the
conditions of maintenance and supervision assure
that only qualified persons will service the
installation
[See Section 336.10(3)] .
Where a cable tray wiring system containing Type
TC cables will be exposed to any significant amount
of hot metal splatter from welding or the torch
cutting of metal during construction or maintenance
activities, temporary metal or plywood covers should
be installed on the cable tray in the exposure areas
to prevent cable jacket and conductor insulation
damage. It is desirable to use only quality Type TC
cables that will pass the IEEE 383 and UL Vertical
Flame Tests (70,000 BTU/hr). Type TC cable
assemblies may contain optical fiber members as per
the UL 1277 standard.
Type ITC Cable: Instrumentation Tray Cable
(Article 727). Although this was a new cable article
in the 1996 NEC
® , it is not a new type of cable.
Thousands of miles of ITC cable have been installed
in industrial situations since the early 1960’s. This
is a multiconductor cable that most often has a
nonmetallic jacket. The No. 22 through No. 12
insulated conductors in the cables are 300 volt
rated. A metallic shield or a metallized foil shield
with a drain wire usually encloses the cable’s
conductors. These cables are used to transmit the
low energy level signals associated with the industrial
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Cable Tray Manual Cooper B-Line, Inc