National Electrical Code References
2002 NEC Cable Requirements
UL Grounding Requirements
The types of cables permitted by the 2002 NEC are
indicated in Table 392.3 (A), Uses Permitted, Wiring
Methods.They include:
All Quick Tray Wire Mesh CableTrays are UL classified with
regard to suitability for use as an Equipment Grounding
Conductor (EGC). Compliance with other appropriate
NEC cable articles is required.The Cable Tray Institute
(CTI) recommends compliance with National Electrical
Manufacturers, NEMA, Standards Publications Nos.VE1 and
VE2, and with the manufacturer's recommendations.
• Power and Control Tray Cable (Type TC) - NEC
Article 340
• Power Limited Tray Cable (Type PLTC) - NEC Sections
725-61 and 725-71
• Instrument Tray Cable (Type ITC) - NEC Article 727
• Optical Fiber Cables - Article 770
• Fire Alarm Circuit Conductors - Article 760
• Communication Cables - Article 800
• Mineral Insulated (MI) Cable - Article 333
• Metal Clad (MC) Cable - Article 334
Other cables, particularly those specially approved for
installation in cable trays, may also be permitted. Medium
voltage (type MV) and single conductor cables in sizes 1/0
and larger are permitted, with some restrictions, in
industrial establishments where qualified persons service
the installation.
All Quick Tray Wire Mesh CableTray systems must
be grounded [392.7(A)]. This is true whether or not
the tray is being used as an equipment ground.There are
many ways to meet this requirement.The most effective
method is to treat the tray as if it were an equipment
ground, meaning that the whole system is continuously
bonded. However, the general requirement only calls for
each section to be grounded.
In order to be used as an equipment ground, several
requirements must be met [392.7(B)]. First, the system
must be bonded: where two sections meet, the connection
should be solidly connected by an approved means, that is,
a bolted connection. Additionally, supervision must ensure
that only qualified personnel service the cable tray system
[392.3(C)].
Therefore, when using Quick Tray Wire Mesh CableTray as
an equipment grounding conductor, maintain continuous
grounding by using the tray in conjunction with "nut and
bolt" and steel splices as shown below.
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Data subject to change without notice
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National Electrical Code References
Additional Options for Grounding
• Use a single conductor cable as the common EGC for all
the circuits in the cable tray [NEC Section 392-3(b)(1)
Exception 2].
• Use individual EGC conductors in each multiconductor
cable in the cable tray (NEC Section 250-95).
Walking on Cable Trays
Walking on cable trays must not be permitted. It violates
the new version of NEMA standard VE-2, manufacturers'
marking and recommendations, and the intent of the NFPA
70 Electrical Safety in Employee Work Practices.Walking on
electrical equipment, conduits, cables or other electrical
systems should also be avoided. In addition to the fall
hazard, there is the risk of damage to equipment and
possible contact with conductors.
High Voltage Cables
High voltage cables can be installed in Quick Tray Wire
Mesh CableTray. NEC permits type MC (Article 334) and
type MV (Article 326) in industrial establishments where
qualified persons will service the installation.
Multiconductor cables rated over 600 volts must be
separated from lower voltage cables by a separate cable
tray or a solid fixed barrier.Type MC cables can be mixed
with lower voltage cables. See NEC 392-6(f).
National Electrical Code Uses Permitted Article 392.3A
Cable Type
Article
Armored Cable
320
Communications Raceway
800
Electrical Metallic Tubing
358
Electrical Nonmetallic Tubing
362
Fire Alarm Cables
760
Flexible Metal Conduit
348
Flexible Metal Tubing
360
Instrumentation Tray Cable
727
Liquid-tight Flexible Metal Conduit
350
Liquid-tight Flexible Nonmetallic Conduit
350
Metal-clad Cable
330
Mineral-insulated, Metal-sheathed Cable
332
Multiconductor Service Entrance Cable
338
Multiconductor Underground Feeder and Branch Circuit Cable
340
Multipurpose and Communications Cables
800
Nonmetallic Sheathed Cable
334
Power and Control Tray Cable
Power-limited Tray Cablesa
336
–
Optical Fiber Cables
770
aSections 725-61 (c) and 721-71 (f).
Instrumentation, Signal, and
Telecommunications Cables
Instrumentation, signal, and telecommunications cabling
should be separated from power cabling, both to meet NEC
requirements and to avoid noise and electromagnetic pickup from adjacent power cables.This can be accomplished by
a separate cable tray system or by a divider within a cable
tray.The requirements for cables that have an outer metal
armor are less stringent than for plastic jacketed cables.The
general rule is to separate communication, control, signal,
and instrumentation cabling from power cabling. Power
cabling includes 460 volt motor power, 120 volt power, and
lighting circuits. Note that 120 volt circuits can generate
noise. Generally, a separation of two inches (51mm) is
minimum, but the individual circuit and cable are the
determining factors in separation requirements.
Data subject to change without notice
☎
763 422 2211 • FAX 763 422 2600 • www.hoffmanonline.com
© 2004 Hoffman Enclosures Inc
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