Cooper Bussmann CT02MAN - Manual (Page 14)

Cable Tray Materials
Metallic cable trays are readily available in aluminum,
pregalvanized steel, hot-dip galvanized after
fabrication, and stainless steel. Aluminum cable tray
should be used for most installations unless specific
corrosion problems prohibit its use. Aluminum's light
weight significantly reduces the cost of installation
when compared to steel.
A fine print note has been added in the 2002 NEC ®
that references the National Electrical Manufacturers
Association (NEMA) documents for further
information on cable tray. These documents: NEMA
VE-1, Metal Cable Tray Systems; NEMA VE-2,
Cable Tray Installation Guidelines; and NEMA FG-1,
Non Metallic Cable Tray Systems, are an excellent
industry resource in the application, selection, and
installation of cable trays both metallic and non
metallic. Contact Cooper B-Line for more
information concerning these helpful documents.
392.2. Definition. Cable Tray System.
This section states that cable tray is a rigid
structural support system used to securely fasten or
support cables and raceways. Cable trays are not
raceways. Cable trays are mechanical supports just
as strut systems are mechanical supports. NEC
®
Article 392 - Cable Trays is an article dedicated to a
type of mechanical support. It is very important that
the personnel involved with engineering and
installing cable tray utilize it as a mechanical support
system and not attempt to utilize it as a raceway
system. There are items in the NEC
® that apply to
raceways and not to cable tray. There are also items
in the NEC
® that apply to cable tray and not to
raceways. These differences will be covered at the
appropriate locations in this manual.
3 9 2 . 3 . U s e s P e r m i t t e d . C a b l e t r a y
i n s t a l l a t i o n s s h a l l n o t b e l i m i t e d t o
industrial establishments.
The text in Section 392.3 clearly states that cable
tray may be used in non-industrial establishments.
The use of cable tray should be based on sound
engineering and economic decisions.
For clarity, the NEC ® now lists all types of circuits
to explicitly permit their use in cable trays. These
circuit types include: services, feeders, branch
circuits, communication circuits, control circuits, and
signaling circuits.
The 2002 NEC ® also added a new requirement
that where cables in tray are exposed to the direct
rays of the sun, they shall be identified as sunlight
resistant for all occupancies, not just industrial.
392.3. Uses Permitted. (A) Wiring
Methods.
This section identifies the 300 & 600 volt
multiconductor cables that may be supported by
cable tray. The "Uses Permitted" or "Uses Not
Permitted" sections in the appropriate NEC
® cable
articles provide the details as to where that cable
type may be used. Where the cable type may be
used, cable tray may be installed to support it except
as per Section 392.4 which states that cable trays
shall not be installed in hoistways or where subject
to severe physical damage. Where not subject to
severe physical damage, cable tray may be used in
any hazardous (classified) area to support the
appropriate cable types in accordance with the
installation requirements of the various Articles that
make up NEC
® Chapter 5 or in any non-hazardous
(unclassified) area.
It should be noted that Section 300.8 of
the NEC ® states that cable trays containing
electric conductors cannot contain any other
service that is not electrical. This includes
any pipe or tube containing steam, water, air,
gas or drainage.
For commercial and industrial cable tray wiring
systems: Type ITC, Type MC, Type TC, and Type
PLTC multiconductor cables are the most commonly
used cables. Type MI and Optical-Fiber cables are
special application cables that are desirable cables
for use in some cable tray wiring systems. The
following paragraphs provide information and
comments about these cable types.
Type MI Cable: Mineral-Insulated, Metal
Sheathed Cable (Article 332). This cable has a
liquid and gas tight continuous copper sheath over
its copper conductors and magnesium oxide
insulation. Developed in the late 1920's by the
French Navy for submarine electrical wiring systems,
properly installed MI cable is the safest electrical
wiring system available. In Europe, Type MI cable
has had a long, successful history of being installed
(with PVC jackets for corrosion protection) in cable
trays as industrial wiring systems. This cable may be
installed in hazardous (classified) areas or in non-
hazardous (unclassified) areas. The single limitation
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Cooper B-Line, Inc Cable Tray Manual