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instrumentation and data handling systems. These
are very critical circuits that impact on facility safety
and on product quality. Type ITC cable must be
supported and secured at intervals not exceeding 6
feet
[See Section 727.4].
Type ITC Cable may be installed in cable trays in
hazardous (classified) areas as permitted in Articles
392, 501, 502, 504 and 505. It states in Article
727 that Type ITC cables that comply with the
crush and impact requirements of Type MC cable
and are identified for such use, are permitted as
open wiring in lengths not to exceed 50 ft. between
a cable tray and the utilization equipment or device.
Where a cable tray wiring system containing Type
ITC 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 to prevent cable jacket
or conductor insulation damage. It is desirable to use
only quality Type ITC cables that will pass the IEEE
383 and UL Vertical Flame Tests (70,000BTU/hr).
Type PLTC Cable: Power-Limited Tray Cable
(Sections 725-61(C), and 725-71(E)). This is a
multiconductor cable with a flame retardant
nonmetallic sheath. The No. 22 through No. 12
insulated conductors in the cables are 300 volt
rated. A metallic shield or a metallized foil shield
with drain wire usually encloses the cable's
conductors. This cable type has high usage in
communication, data processing, fire protection,
signaling, and industrial instrumentation wiring
systems.
There are versions of this cable with insulation and
jacket systems made of materials with low smoke
emission and low flame spread properties which
make them desirable for use in plenums. In
Industrial Establishments where the conditions of
maintenance and supervision ensure that only
qualified persons service the installation and where
the cable is not subject to physical damage Type
PLTC cable may be installed in cable trays
hazardous (classified) areas as permitted in Section
501.4(B), 502.4(B) and 504.20. Type PLTC cables
that comply with the crush and impact requirements
of Type MC cable and are identified for such use,
are permitted as open wiring in lengths not to
exceed a total of 50 ft. between a cable tray and the
utilization equipment or device. In this situation, the
cable needs to be supported and secured at intervals
not exceeding 6 ft. Where a cable tray wiring system
containing Type PLTC 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 to prevent cable jacket and conductor
insulation damage. It is desirable to use only quality
Type PLTC cables that will pass the IEEE 383 and
UL Vertical Flame Tests (70,000 BTU/hr). Type
PLTC cable assemblies may contain optical fiber
members as per the UL 1277 standard.
Optical Fiber Cables (Article 770). The addition
of optical fiber cables in the Section 392.3(A) cable
list for the 1996 NEC was not a technical change.
Optical fiber cables have been allowed to be
supported in cable trays as per Section 770.6.
Optical fibers may also be present in Type TC
cables as per UL Standard 1277.
For the 1999 NEC
®
code, Article 760 - Fire
Alarm Cables and Articles 800 - Multipurpose and
Communications Cables were added to the list of
cables permitted to be installed in cable tray
systems.
For the 1993 NEC
®
, the general statement in the
1990 NEC
®
which allowed all types of raceways to
be supported by cable trays was replaced by
individual statements for each of the ten specific
raceway types that may now be supported by cable
tray. The chances of any such installations being
made are very low, since strut is a more convenient
and economic choice than cable tray to support
raceway systems.
392.3. Uses Permitted. (B) In Industrial
Establishments.
This section limits the installation of single
conductor cables and Type MV multiconductor
cables in cable trays to qualifying industrial
establishments as defined in this section.
Per the 2002 NEC
®
solid bottom cable trays are
now permitted to support single conductor cables
only in industrial establishments where conditions of
maintenance and supervision ensure that only
qualified persons will service the installed cable tray
system. However, at this time, no fill rules for single
conductor cables in solid bottom cable tray have
been established.
[see Section 392.3(B)]
14
Cooper B-Line, Inc Cable Tray Manual