Cooper Bussmann Ct02Man Users Manual B Line Cable Tray Based On The 2002 National Electrical Code®

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CABLE TRAY MANUAL

Based on the

2002 National Electrical Code®

2002

CT02MAN

Table of Contents Page

No.

Introduction ...................................................................................................................... 2

Why Cable Tray?

Safety .................................................................................................................... 3

Dependability ........................................................................................................... 4

Space Savings .......................................................................................................... 4

Cost Savings ......................................................................................................... 5-8

An In-depth Look at the 2002 NEC®, Section 392

Types of Cable Trays (NEC®392.1 Scope)............................................................ 9-11

EMI/RFI Cable Tray ......................................................................................... 10-11

Cable Tray Materials ............................................................................................... 12

Types of Cables Allowed in Cable Tray [392.3 (A)]..................................................... 12

MI - Mineral Insulated Metal Sheathed Cable [Article 332] ............................... 12

MC - Metal Clad Cable [Article 330] .............................................................. 13

TC - Power and Control Tray Cable [Article 336] ........................................... 13

ITC - Instrumentation Tray Cable [Article 727] ............................................... 13

PLTC - Power Limited Tray Cable [Sections 725.61 (C) and 725.71 (E)] .......... 14

Other Types - Fire Alarm [Article 760],

Multipurpose and Communications Cable [Article 800] ................14

Single Conductor & Type MV Cables [392.3 (B)]....................................................... 14

Cable Tray Use in Hazardous Locations [392.3 (D)].............................................. 15-17

Limitations on Cable Tray Use [392.4] ..................................................................... 18

Cable Tray Loading [392.5 (A)]........................................................................... 18-20

Fiberglass Cable Tray [392.3 (E) & 392.5 (F)]............................................................ 20

Discontinuous Cable Tray and Fittings [392.6 (A)] ................................................ 21-22

Covers [392.6 (D)]................................................................................................... 23

Barriers [392.6 (E) & (F)].......................................................................................... 24

Spacing of Multiple Cable Trays [392.6 (I)] ................................................................ 25

Supporting Conduit from Cable Tray [392.6 (J)] ........................................................ 25

Use of Cable Tray as an Equipment Grounding Conductor [392.7 Grounding]........ 26-29

Fastening Cables [392.8 (B)] .................................................................................... 30

Cable Installation [392.8] ................................................................................... 30-32

Sizing Cable Tray

Multiconductor - 2000 volts or less [392.9]............................................... 32-34

Single conductor - 2000 volts or less [392.10]........................................... 34-36

Type MC or MV - 2001 volts or greater [392.12] ........................................... 37

Ampacities of Cables in Cable Tray .................................................................... 36-38

Cable Tray Wiring System Design and Installation Hints ....................................... 38-39

Fireproofing Tray ................................................................................................... 40

Expansion and Contraction ............................................................................... 41-42

Appendix Index & Appendix Sheets...................................................................... 44-55

Cable Tray Installation & Specification Checklists ........................................... 54-55

Footnotes ..................................................................................................................... 56

1

Cable Tray Manual Cooper B-Line, Inc

INTRODUCTION

The B-Line Cable Tray Manual was produced by B-Line's technical staff. B-Line has recognized

the need for a complete cable tray reference source for electrical engineers and designers. The

following pages address the 2002 National Electric Code®requirements for cable tray systems

as well as design solutions from practical experience. The information has been organized for use as

a reference guide for both those unfamiliar and those experienced with cable tray.

Nearly every aspect of cable tray design and installation has been explored for the use of the

reader. If a topic has not been covered sufficiently to answer a specific question or if additional

information is desired, contact the engineering department at B-Line. We sincerely hope you will

find the B-Line Cable Tray Manual a helpful and informative addition to your technical library.

The information contained herein has been carefully checked for accuracy and is believed to be

correct and current. No warranty, either expressed or implied, is made as to either its applicability

to, or its compatibility with, specific requirements, of this information, nor for damages consequent

to its use. All design characteristics, specifications, tolerances and similar information are subject to

change without notice.

Cooper B-Line, Inc.

509 West Monroe Street

Highland, IL 62249-0326

Tel: (618) 654-2184

Fax: (618) 654-5499

National Electrical Code®and NEC®are registered trademarks of the

National Fire Protection Association, Inc. Quincy, MA 02269.

2

Cooper B-Line, Inc Cable Tray Manual

Large numbers of electrical engineers have

limited detail knowledge concerning wiring systems.

There is the tendency by engineers to avoid

becoming involved in the details of wiring systems,

leaving the wiring system selection and design to

designers or contractors. Certain decisions must be

made for any wiring system installation, and these

decisions should be made in the design and

construction activities' chain where maximum

impact is achieved at the lowest possible cost.

Deferring design decisions to construction can

result in increased costs and wiring systems

incompatible with the owner's future requirements.

Early in the project's design life, the costs and

features of various applicable wiring systems should

be objectively evaluated in detail. Unfortunately,

such evaluations are often not made because of the

time and money involved. It is important to realize

that these initial evaluations are important and will

save time and money in the long run. The

evaluation should include the safety, dependability,

space and cost requirements of the project. Many

industrial and commercial electrical wiring systems

have excessive initial capital costs, unnecessary

power outages and require excessive maintenance.

Moreover, the wiring system may not have the

features to easily accommodate system changes

and expansions, or provide the maximum degree of

safety for the personnel and the facilities.

Cable tray wiring systems are the preferred wiring

system when they are evaluated against equivalent

conduit wiring systems in terms of safety,

dependability, space and cost. To properly evaluate

a cable tray wiring system vs. a conduit wiring

system, an engineer must be knowledgeable of both

their installation and the system features. The

advantages of cable tray installations are listed

below and explained in the following paragraphs.

• Safety Features

• Dependability

• Space Savings

• Cost Savings

• Design Cost Savings

• Material Cost Savings

• Installation Cost & Time Savings

• Maintenance Savings

CABLE TRAY SAFETY FEATURES

A properly engineered and installed cable tray

wiring system provides some highly desirable safety

features that are not obtainable with a conduit wiring

system.

•Tray cables do not provide a significant path for

the transmission of corrosive, explosive, or toxic

gases while conduits do. There have been explosions

in industrial facilities in which the conduit systems

were a link in the chain of events that set up the

conditions for the explosions. These explosions

would not have occurred with a cable tray wiring

system since the explosive gas would not have been

piped into a critical area. This can occur even

though there are seals in the conduits. There does

have to be some type of an equipment failure or

abnormal condition for the gas to get into the

conduit, however this does occur. Conduit seals

prevent explosions from traveling down the conduit

(pressure piling) but they do not seat tight enough to

prevent moisture or gas migration until an explosion

or a sudden pressure increase seats them. The

October 6, 1979 Electrical Substation Explosion at

the Cove Point, Maryland Columbia Liquefied

Natural Gas Facility is a very good example of where

explosive gas traveled though a two hundred foot

long conduit with a seal in it. The substation was

demolished, the foreman was killed and an operator

was badly burned. This explosion wouldn’t have

occurred if a cable tray wiring system had been

installed instead of a conduit wiring system. A New

Jersey chemical plant had the instrumentation and

electrical equipment in one of its control rooms

destroyed in a similar type incident.

•In addition to explosive gases, corrosive gases

and toxic gases from chemical plant equipment

failures can travel through the conduits to equipment

or control rooms where the plant personnel and the

sensitive equipment will be exposed to the gases.

•In facilities where cable tray may be used as the

equipment grounding conductor in accordance with

NEC

®

Sections 392.3(C) & 392.7, the grounding

equipment system components lend themselves to

visual inspection as well as electrical continuity checks.

WHY CABLE TRAY?

BECAUSE A CABLE TRAY WIRING SYSTEM PROVIDES

SAFE AND DEPENDABLE WAYS TO SAVE NOW AND LATER

3

Cable Tray Manual Cooper B-Line, Inc

CABLE TRAY DEPENDABILITY

A properly designed and installed cable tray

system with the appropriate cable types will provide

a wiring system of outstanding dependability for the

control, communication, data handling,

instrumentation, and power systems. The

dependability of cable tray wiring systems has been

proven by a 40 year track record of excellent

performance.

•Cable tray wiring systems have an outstanding

record for dependable service in industry. It is the

most common industrial wiring system in Europe.

In continuous process systems, an electrical system

failure can cost millions of dollars and present

serious process safety problems for the facility, its

personnel and the people in the surrounding

communities. A properly designed and installed

cable tray system with the appropriate cable types

will provide a wiring system of outstanding

dependability for process plants.

•Television broadcast origination facilities and

studios make use of cable tray to support and route

the large volumes of cable needed for their

operations with a high degree of dependability. It

would be impossible to have the wiring system

flexibility they need with a conduit wiring system.

•Large retail and warehouse installations use

cable tray to support their data communication

cable systems. Such systems must be dependable so

that there are no outages of their continuous

inventory control systems.

•Cable tray wiring systems have been widely

used to support cabling in both commercial and

industrial computer rooms overhead and beneath

the floor to provide orderly paths to house and

support the cabling. These types of installations

need a high degree of dependability which can be

obtained using cable tray wiring systems.

CABLE TRAY SPACE SAVINGS

When compared to a conduit wiring system, an

equivalent cable tray wiring system installation

requires substantially less space.

Increasing the size of a structure or a support

system to handle a high space volume conduit

wiring system is unnecessary when this problem can

be avoided by the selection of a cable tray wiring

system.

•Facilities with high density wiring systems

devoted to control, instrumentation, data handling

and branch circuit wiring have the choice of

selecting cable tray or conduit wiring systems. A

conduit wiring system is often a poor choice

because large conduit banks require significant

space, competing with other systems and

equipment. Choosing a cable tray wiring system

greatly reduces this problem.

•Financial institutions with large computer

installations have high density wiring systems under

floors or in overhead plenum areas that are best

handled by cable tray wiring systems.

•Airport facilities have extensive cable tray

wiring systems to handle the ever expanding needs

of the airline industry.

•Cable tray is used in many facilities because of

the ever present need of routing more and more

cables in less space at lower costs.

•Large health care facilities have high density

wiring systems that are ideal candidates for cable

tray.

4

Cooper B-Line, Inc Cable Tray Manual

CABLE TRAY WIRING SYSTEM

COST SAVINGS

Usually, the initial capital cost is the major factor

in selecting a project's wiring system when an

evaluation is made comparing cable tray wiring

systems and conduit wiring systems. Such an

evaluation often covers just the conductors, material,

and installation labor costs. The results of these

initial cost evaluations usually show that the installed

cable tray wiring system will cost 10 to 60 percent

less than an equivalent conduit wiring system. The

amount of cost savings depends on the complexity

and size of the installation.

There are other savings in addition to the initial

installation cost savings for cable tray wiring systems

over conduit wiring systems. They include reduced

engineering costs, reduced maintenance costs,

reduced expansion costs, reduced production losses

due to power outages, reduced environmental

problems due to continuity of power and reduced

data handling system costs due to the continuity of

power. The magnitudes of many of these costs

savings are difficult to determine until the condition

exists which makes them real instead of potential

cost savings.

DESIGN COST SAVINGS

•Most projects are roughly defined at the start of

design. For projects that are not 100 percent

defined before design start, the cost of and time

used in coping with continuous changes during the

engineering and drafting design phases will be

substantially less for cable tray wiring systems than

for conduit wiring systems. A small amount of

engineering is required to change the width of a

cable tray to gain additional wiring space capacity.

Change is a complex problem when conduit banks

are involved.

•The final drawings for a cable tray wiring

system may be completed and sent out for bid or

construction more quickly than for a conduit wiring

system. Cable tray simplifies the wiring system

design process and reduces the number of details.

•Cable tray wiring systems are well suited for

computer aided design drawings. A spread sheet

based wiring management program may be used to

control the cable fills in the cable tray. While such a

system may also be used for controlling conduit fill,

large numbers of individual conduits must be

monitored. For an equal capacity wiring system,

only a few cable tray runs would have to be

monitored.

•Dedicated cable tray installation zones alert

other engineering disciplines to avoid designs that

will produce equipment and material installation

conflicts in these areas. As more circuits are added,

the cable tray installation zone will increase only a

few inches; the space required for the additional

conduits needed would be much greater.

•The fact that a cable can easily enter and

exit cable tray anywhere along its route,

allows for some unique opportunities that provide

highly flexible designs.

•Fewer supports have to be designed and less

coordination is required between the design

disciplines for the cable tray supports compared to

conduit supports.

MATERIAL COST SAVINGS

•Excluding conductors, the cost of the cable

trays, supports, and miscellaneous materials will

provide a savings of up to 80% as compared to the

cost of the conduits, supports, pull boxes, and

miscellaneous materials. An 18 inch wide cable tray

has an allowable fill area of 21 square inches. It

would take 7 - 3 inch conduits to obtain this

allowable fill area (7 x 2.95 square inches = 20.65

square inches).

•The cost of 600 volt insulated multiconductor

cables listed for use in cable tray is greater than the

cost of 600 volt insulated individual conductors used

in conduit. The cost differential depends on the

insulation systems, jacket materials and cable

construction.

•For some electrical loads, parallel conductors

are installed in conduit and the conductors must be

derated, requiring larger conductors to make up for

the deration. If these circuits were installed in cable

tray, the conductor sizes would not need to be

increased since the parallel conductor derating

factors do not apply to three conductor or single

conductor cables in cable tray.

•Typical 300 volt insulated multiconductor

instrumentation tray cables (ITC) and power limited

tray cables (PLTC) cost the same for both cable tray

and conduit wiring systems. This applies for

instrumentation circuits, low level analog and digital

5

Cable Tray Manual Cooper B-Line, Inc

signal circuits, logic input/output (I/O) circuits, etc.

There are other cable tray installations which require

a higher cost cable than the equivalent conduit

installation. Such installations are limited to areas

where low smoke emission and/or low flame spread

ITC or PLTC cables must be used.

•Conduit banks often require more frequent and

higher strength supports than cable trays. 3 inch

and larger rigid metal conduits are the only sizes

allowed to be supported on 20 foot spans [National

Electrical Code®(NEC®) Table 344.30(B)(2)].

•When a cable tray width is increased 6 inches,

the cable tray cost increase is less than 10 percent.

This substantially increases the cable tray’s wiring

capacity for a minimal additional cost. To obtain

such an increase in capacity for a conduit wiring

system would be very costly.

INSTALLATION COST AND

TIME SAVINGS

•Depending on the complexity and magnitude of

the wiring system, the total cost savings for the

initial installation (labor, equipment and material)

may be up to 60 percent for a cable tray wiring

system over a conduit wiring system. When there

are banks of conduit to be installed that are more

than 100 feet long and consist of four or more 2

inch conduits or 12 or more smaller conduits, the

labor cost savings obtained using cable tray wiring

systems are very significant.

•Many more individual components are involved

in the installation of a conduit system and its

conductors compared to the installation of a cable

tray system and its cables. This results in the

handling and installing of large amounts of conduit

items vs. small amounts of cable tray items for the

same wiring capacity.

6

16000

14000

12000

10000

8000

6000

4000

2000

0

Total

Installed

Cost ($)

COST - Cable Tray vs. Conduit

(Equivalent Conductor Fill Areas)

Material Cost

Labor Cost @

$25/hr per NECA

labor units.

Ladder

Cable Tray

1

Solid Bottom

Cable Tray

2

EMT

3

Rigid Steel

Conduit

4

Installation: 200 linear feet of cable supported with four 90° direction changes and all

trapeze supports on 8 ft. spans.

1. Hot dip galvanized steel, 18" wide, ladder cable tray (9" rung spacing) with all hardware.

2. Hot dip galvanized steel, 18" wide, solid bottom cable tray and all hardware.

3. 7 parallel runs of 3" diameter EMT with concentric bends.

4. 7 parallel runs of 3" diameter galvanized conduit with concentric bends.

Note: Above costs are historical figures and do not include cable and cable pulling costs. Cable costs differ

per installation and cable/conductor pulling costs have been shown to be considerably less for cable

tray than for conduit.

Cooper B-Line, Inc Cable Tray Manual

•The higher the elevation of the wiring system,

the more important the number of components

required to complete the installation. Many

additional man-hours will be required just moving

the components needed for the conduit system up

to the work location.

•Conduit wiring systems require pull boxes or

splice boxes when there is the equivalent of more

than 360 degrees of bends in a run. For large

conductors, pull or junction boxes may be required

more often to facilitate the conductor’s installation.

Cable tray wiring systems do not require pull boxes

or splice boxes.

•Penetrating a masonry wall with cable tray

requires a smaller hole and limited repair work.

•More supports are normally required for rigid

steel conduit due to the requirements of NEC®

Table 344.30(B)(2).

•Concentric conduit bends for direction changes

in conduit banks are very labor intensive and difficult

to make. However if they are not used, the

installation will be unattractive. The time required to

make a concentric bend is increased by a factor of

3-6 over that of a single shot bend. This time

consuming practice is eliminated when cable tray

wiring systems are used.

•Conductor pulling is more complicated and time

consuming for conduit wiring systems than for cable

tray wiring systems. Normally, single conductor wire

pulls for conduit wiring systems require multiple reel

setups. For conduit wiring systems, it is necessary to

pull from termination equipment enclosure to

termination equipment enclosure. Tray cables being

installed in cable trays do not have to be pulled into

the termination equipment enclosures. Tray cable

may be pulled from near the first termination

enclosure along the cable tray route to near the

second termination enclosure. Then, the tray cable

is inserted into the equipment enclosures for

termination. For projects with significant numbers of

large conductors terminating in switchgear, this may

be a very desirable feature that can save hours of an

electrician's time. Unnecessary power outages can

be eliminated since tray cable pulls may be made

without de-energizing the equipment. For conduit

installations, the equipment will have to be de-

energized for rubber safety blanketing to be

installed, otherwise the conductor pulls might have

to be made on a weekend or on a holiday at

premium labor costs to avoid shutting down

production or data processing operations during

normal working hours.

•Conductor insulation damage is common in

conduits since jamming can occur when pulling the

conductors. Jamming is the wedging of conductors

in a conduit when three conductors lay side by side

in a flat plane. This may occur when pulling around

bends or when the conductors twist. Ninety-two

percent of all conductor failures are the result of the

conductor’s insulation being damaged during the

conductor’s installation. Many common

combinations of conductors and conduits fall into

critical jam ratio values. Critical jam ratio (J.R.=

Conduit ID/Conductor OD) values range from 2.8

to 3.2. The J. R. for 3 single conductor

THHN/THWN insulated 350 kcmil conductors in a

21/2inch conduit would be 3.0 (2.469 inches/

0.816 inches). If conductor insulation damage

occurs, additional costs and time are required for

replacing the conductors. This cannot occur in a

cable tray wiring system.

•Smaller electrician crews may be used to install

the equivalent wiring capacity in cable tray. This

allows for manpower leveling, the peak and average

crew would be almost the same number, and the

electrician experience level required is lower for

cable tray installations.

•Since the work is completed faster there is less

work space conflict with the other construction

disciplines. This is especially true if installations are

elevated and if significant amounts of piping are

being installed on the project.

MAINTENANCE SAVINGS

•One of the most important features of cable

tray is that tray cable can easily be installed in

existing trays if there is space available. Cable tray

wiring systems allow wiring additions or

modifications to be made quickly with minimum

disruption to operations. Any conceivable change

that is required in a wiring system can be done at

lower cost and in less time for a cable tray wiring

system than for a conduit wiring system.

7

Cable Tray Manual Cooper B-Line, Inc

•Moisture is a major cause of electrical

equipment and material failures. Breathing due to

temperature cycling results in the conduits

accumulating relatively large amounts of moisture.

The conduits then pipe this moisture into the

electrical equipment enclosures which over a period

of time results in the deterioration of the equipment

insulation systems and their eventual failure. Also,

moisture may become a factor in the corrosion

failure of some of the critical electrical equipment's

metallic components. Conduit seals are not effective

in blocking the movement of moisture. The conduit

systems may be designed to reduce the moisture

problems but not to completely eliminate it. Few

designers go into the design detail necessary to

reduce the effects of moisture in the conduit

systems. Tray cables do not provide internal

moisture paths as do conduits.

•In the event of external fires in industrial

installations, the damage to the tray cable and cable

tray is most often limited to the area of the flame

contact plus a few feet on either side of the flame

contact area. For such a fire enveloping a steel

conduit bank, the steel conduit is a heat sink and the

conductor insulation will be damaged for a

considerable distance inside the conduit.

Thermoplastic insulation may be fused to the steel

conduit and the conduit will need to be replaced for

many feet. This occurred in an Ohio chemical plant

and the rigid steel conduits had to be replaced for

90 feet. Under such conditions, the repair cost for

fire damage would normally be greater for a conduit

wiring system than for cable tray and tray cable. In

the Ohio chemical plant fire, there were banks of

conduits and runs of cable tray involved. The cable

tray wiring systems were repaired in two days. The

conduit wiring systems were repaired in six days and

required a great deal more manpower.

•In the event of an external fire, the conduit

becomes a heat sink and an oven which decreases

the time required for the conductor insulation

systems to fail. The heat decomposes the cable

jackets and the conductor insulation material. If

these materials contain PVC as do most cables,

hydrogen chloride vapors will come out the ends of

the conduits in the control rooms. These fumes are

very corrosive to the electronic equipment. They are

also hazardous to personnel. A flame impingement

on a cable tray system will not result in the fumes

going into the control room as there is no

containment path for them. They will be dispersed

into the atmosphere.

IN MOST CASES AN OBJECTIVE

EVALUATION OF THE REQUIREMENTS

FOR MOST HIGH DENSITY WIRING

SYSTEMS WILL SHOW THAT A CABLE

TRAY WIRING SYSTEM PROVIDES A

WIRING SYSTEM SUPERIOR TO A

CONDUIT WIRING SYSTEM.

Abandoned Cables

Easily identified, marked, or removed - all

possible from an open Cable Tray System

For the 2002 National Electrical Code, several

proposals were submitted to the NFPA to revise the

1999 NEC®for Articles 300, 640, 645, 725, 760,

770, 800, 820, and 830 to require all abandoned

cables to be removed from plenum spaces.

The purpose of the proposals is to remove the

cables as a source of excess combustibles from

plenums and other confined spaces such as raised

floors and drop ceilings. All of the Code Making

Panels agreed that this should be acceptable practice

except Code Making Panel 3, which oversees

Article 300.

Because Article 300 is exempt from this

requirement only low-voltage and communication

cables are affected.

Each Article adopted a definition of abandoned

cables and the rule for removal. The general

consensus is that abandoned cable is cable that is

not terminated at equipment or connectors and is

not identified for future use with a tag. Please refer

to each individual NEC®Article for specifics.

Having to tag, remove, or rearrange cables within

an enclosed raceway can be a time consuming and

difficult job. Without being able to clearly see the

cables and follow their exact routing throughout a

facility, identifying abandoned cables would be very

difficult and expensive.

With the open accessibility of cable tray, these

changes can be implemented with ease. Abandoned

cables can be identified, marked, rearranged, or

removed with little or no difficulty.

8

Cooper B-Line, Inc Cable Tray Manual

392.1. Scope.

Of the types of cable trays listed in this section,

ladder cable tray is the most widely used type of

cable tray due to several very desirable features.

•The rungs provide a convenient anchor for

tying down cables in vertical runs or where the

positions of the cables must be maintained in

horizontal runs.

•Cables may exit or enter through the top or the

bottom of the tray.

•A ladder cable tray without covers provides for

the maximum free flow of air, dissipating heat

produced in current carrying conductors.

•Moisture cannot accumulate in ladder cable

trays and be piped into electrical equipment as

happens in conduit systems.

•Ladder cable tray cannot pipe hazardous or

explosive gasses from one area to another as

happens with conduit systems.

• In areas where there is the potential for dust to

accumulate, ladder cable trays should be installed.

The dust buildup in ladder cable trays will be less

than the dust buildup in ventilated trough or solid

bottom cable trays.

Ladder cable trays are available in widths of 6, 9,

12, 18, 24, 30, 36, and 42 inches with rung

spacings of 6, 9, 12, or 18 inches. Wider rung

spacings and wider cable tray widths decrease the

overall strength of the cable tray. Specifiers should

be aware that some cable tray manufacturers do not

account for this load reduction in their published

cable tray load charts. B-Line uses stronger rungs in

wider cable trays to safely bear the loads published.

With one exception, the specifier selects the rung

spacing that he or she feels is the most desirable for

the installation. The exception is that 9 inches is the

maximum allowable rung spacing for a ladder cable

tray supporting any 1/0 through 4/0 single

conductor cables [See Section 392.3(B)(1)(a)].

Where the ladder cable tray supports small

diameter multiconductor control and

instrumentation cables; 6, 9, or 12 inch rung

spacings should be specified. Quality Type TC,

Type PLTC, or Type ITC small diameter

multiconductor control and instrumentation cables

will not be damaged due to the cable tray rung

spacing selected, but the installation may not appear

neat if there is significant drooping of the cables

between the rungs.

For ladder cable trays supporting large power

cables, 9 inch or wider rung spacings should be

selected. For many installations, the cable trays are

routed over the top of a motor control center (MCC)

or switchgear enclosure. Cables exit out the bottom

of the cable trays and into the top of the MCC or

switchgear enclosure. For these installations, the

cable manufacturer's recommended minimum

bending radii for the specific cables must not be

violated. If the rung spacing is too close, it may be

necessary to remove some rungs in order to

maintain the proper cable bending radii. This

construction site modification can usually be avoided

by selecting a cable tray with 12 or 18 inch rung

spacing.

If you are still uncertain as to which rung spacing

to specify, 9 inch rung spacing is the most common

and is used on 80% of the ladder cable tray sold.

9

Standard Aluminum Ladder

AN IN-DEPTH LOOK AT 2002 NEC®

ARTICLE 392 - CABLE TRAY

(The following code explanations are to be used with a copy of the 2002 NEC®.)

To obtain a copy of the NEC®contact:

National Fire Protection Association®

1 Batterymarch Park • P.O. Box 9101

Quincy, Massachusetts 02269-9101

1-800-344-3555

Cable Tray Manual Cooper B-Line, Inc

The 1999 NEC®added the word ‘ventilated’ in

front of trough to clear up some confusion that solid

trough is treated the same as ventilated trough. It is

not. Solid trough is recognized as solid bottom cable

tray.

Ventilated trough cable tray is often used when the

specifier does not want to use ladder cable tray to

support small diameter multiconductor control and

instrumentation cables. As no drooping of the small

diameter cables is visible, ventilated trough cable

trays provide neat appearing installations. Small

diameter cables may exit the ventilated trough cable

tray through the bottom ventilation holes as well as

out the top of the cable tray. For installations where

the cables exit the bottom of the cable tray and the

system is subject to some degree of vibration, it is

advisable to use B-Line Trough Drop-Out Bushings

(Cat. No. 99-1124). These snap-in bushings provide

additional abrasion protection for the cable jackets.

Just as for ladder cable tray, ventilated trough cable

tray will not pipe moisture into electrical equipment.

Standard widths for ventilated trough cable tray

systems are 6, 9, 12, 18, 24, 30, and 36 inches.

The standard bottom configuration for ventilated

trough cable tray is a corrugated bottom with 2 7/8

inch bearing surfaces - 6 inches on centers and 2

1/4inch x 4 inch ventilation openings. Since a

corrugated bottom cannot be bent horizontally, the

standard bottom configuration for horizontal bend

fittings consists of rungs spaced on 4 inch centers.

This difference in bottom construction may be

objectionable to some owners, so be sure you are

aware of the owner's sensitivity to aesthetics for the

cable tray installation.

Channel cable tray systems (B-Line's cable

channel) are available in 3, 4, and 6 inch widths

with ventilated or solid bottoms. The 2002 NEC®

now recognizes solid bottom cable channel.

Prior to the 2002 Code, the NEC®did not have

any specific provisions for the use of solid cable

channel.

Instead of large conduits, cable channel may be

used very effectively to support cable drops from the

cable tray run to the equipment or device being

serviced and is ideal for cable tray runs involving a

small number of cables. Cable channel may also be

used to support push buttons, field mounted

instrumentation devices, etc. Small diameter cables

may exit ventilated cable channel through the

bottom ventilation holes, out the top or through the

end. For installations where the cables exit through

the ventilation openings and the cable channel or

the cables are subject to some degree of vibration, it

is advisable to use B-Line Cable Channel Bushings

(Cat. No. 99-1125). These snap-in plastic bushings

provide additional abrasion protection for the cable

jackets.

Some specifiers prefer solid bottom cable tray to

support large numbers of small diameter control and

multiconductor instrumentation cables. Solid bottom

steel cable trays with solid covers and wrap around

cover clamps can be used to provide EMI/RFI

shielding protection for sensitive circuits.

Unlike ladder and ventilated trough cable trays,

solid bottom cable trays can collect and retain

moisture. Where they are installed outdoors or

indoors in humid locations and EMI/RFI shielding

protection is not required, it is recommended that

1/4inch weep holes be drilled in their bottoms at

the sides and in the middle every 3 feet to limit

water accumulation.

10

Vent. Channel Cable Tray

(B-Line's Cable Channel)

Aluminum Solid Bottom Trough

Cooper B-Line, Inc Cable Tray Manual

Steel Ventilated Trough

The words "and other similar structures." were

incorporated in Section 392.1 for future types of

cable tray that might be developed, such as center

supported type cable tray. All the technical

information developed by the 1973 NEC®

Technical Subcommittee on Cable Tray for Article

318 - Cable Trays was based on cable trays with

side rails and this technical information is still the

basis for the 2002 NEC®Article 392 - Cable Trays.

The standard lengths for cable trays are 10, 12,

20 and 24 feet (consult B-Line for the availability of

nonstandard cable tray lengths). Selecting a cable

tray length is based on several criteria. Some of

these criteria include the required load that the cable

tray must support, the distance between the cable

tray supports, and ease of handling and installation.

One industry standard that is strongly

recommended is that only one cable splice be

placed between support spans and, for long

span trays, that they ideally be place at 1/4-span.

This automatically limits the length of tray you

choose, as the tray must be longer than or equal to

the support span you have selected. Matching the

tray length to your support span can help ensure

that your splice locations are controlled.

Cable trays can be organized into 4 categories:

Short Span, Intermediate Span, Long Span, and

Extra-Long Span.

Short Span trays, typically used for non-industrial

indoor installations, are usually supported every 6 to

8 feet, while Intermediate Span trays are typically

supported every 10 to 12 feet. A 10 or 12 foot

cable tray is usually used for both of these types of

installations. To keep from allowing two splices to

occur between supports, a 12 foot tray should be

used for any support span greater than 10 feet, up

to 12 feet. Placing the cable tray splices at 1/4-span

is not critical in a short or intermediate span

application given that most trays have sufficiently

strong splice plates.

In an indoor industrial installation 10 or 12 foot

tray sections may be easier to handle and install as

you may have piping or ducting to maneuver

around. However, using 20 foot instead of 12 foot

straight sections may provide labor savings during

installation by reducing the number of splice joints.

If this is done, the selected tray system should meet

the loading requirements for the support span you

are using. If you are interested in supporting 100

lbs/ft and you are buying 20 foot tray sections while

supporting it every 12 feet, it isn’t necessary to

specify a NEMA 20C tray (100 lbs/ft on a 20 foot

span). A NEMA 20A tray (50 lbs/ft on a 20 foot

span) will support over 130 lbs/ft when supported

on a 12 ft span with a safety factor of 1.5.

Specifying a 20C tray is not an economical use of

product. If you desire to use 20 foot sections of

cable tray, it makes more sense to increase your

support span up to 20 feet. This not only saves

labor by decreasing the number of splices, but also

by decreasing the number of supports that must be

installed.

Long Span trays are typically supported anywhere

from 14 to 20 foot intervals with 20 feet being the

most popular. In long span situations, the placement

of the splice locations at 1/4-span becomes much

more important. Matching the tray length to your

support span can help control your splice locations.

Extra-Long Span trays are supported on spans

exceeding 20 feet. Some outdoor cable tray

installations may have to span anywhere from 20 to

30 feet to cross roads or to reduce the number of

expensive outdoor supports. The distance between

supports affects the tray strength exponentially;

therefore the strength of the cable tray system

selected should be designed around the specific

support span chosen for that run.

[See Section 392.5(A) on page 18 for additional

information on cable tray strength and rigidity.]

B-Line has many cataloged fittings and accessory

items for ladder, ventilated trough, ventilated

channel, and solid bottom cable trays which

eliminate the need for the costly field fabrication of

such items. When properly selected and installed,

these factory fabricated fittings and accessories

improve the appearance of the cable tray system in

addition to reducing labor costs.

11

Cable Tray Manual Cooper B-Line, Inc

Center Supported Cable Tray

(B-Line’s Cent-R-Rail System)

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.

392.3. Uses Permitted. Cable tray

installations shall not be limited to

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

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

13

Cable Tray Manual Cooper B-Line, Inc

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)]

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Cooper B-Line, Inc Cable Tray Manual

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.

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Cable Tray Manual Cooper B-Line, Inc

501-4(A)(1)(d) allows Type ITC-HL cable 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

and provided with termination fittings listed for the

application.

501.4. Wiring Methods. (B) Class I, Division 2

(Gases or Vapors). Types ITC, PLTC, MI, MC, MV,

or TC cables may be installed in cable tray in this

type of hazardous (classified) area. Under the

conditions specified in Section 501.5(E), Cable seals

are required in Class 1, Division 2 areas. Cable seals

should be used only when absolutely necessary.

501.5. Sealing and Drainage. (E) Cable Seals,

Class 1, Division 2. (1) Cables will be required to be

sealed only where they enter certain types of

enclosures used in Class 1, Division 2 areas. Factory

sealed push buttons are an example of enclosures

that do not require a cable seal at the entrance of

the cable into the enclosure.

501.5. Sealing and Drainage. (E) Cable Seals,

Class 1, Division 2. (2) Gas blocked cables are

available from some cable manufacturers but they

have not been widely used. For gas to pass through

the jacketed multiconductor cable's core, a pressure

differential must be maintained from one end of the

cable to the other end or to the point where there is

a break in the cable's jacket. The existence of such a

condition is extremely rare and would require that

one end of the cable be in a pressure vessel or a

pressurized enclosure and the other end be exposed

to the atmosphere. The migration of any significant

volume of gas or vapor though the core of a

multiconductor cable is very remote. This is one of

the safety advantages that cable tray wiring systems

have over conduit wiring systems. There are

documented cases of industrial explosions caused by

the migration of gases and vapors through conduits

when they came in contact with an ignition source.

There are no known cases of cables in cable tray

wiring systems providing a path for gases or vapors

to an ignition source which produced an industrial

explosion.

501.5. Sealing and Drainage. (E) Cable Seals,

Class 1, Division 2. (3)

Exception: Cables with an unbroken gas/vapor-

tight continuous sheath shall be permitted to pass

through a Class 1, Division 2 location without

seals.

This is an extremely important exception stating

that cable seals are not required when a cable goes

from an unclassified area through a classified area

then back to an unclassified area.

501.5. Sealing and Drainage. (E) Cable Seals,

Class 1, Division 2. (4)

If you do not have a gas/vapor-tight continuous

sheath, cable seals are required at the boundary of

the Division 2 and unclassified location.

The sheaths mentioned above may be fabricated

of metal or a nonmetallic material.

502.4. Wiring Methods. (A) Class II, Division 1

(Combustible Dusts). Type MI cable may be

installed in cable tray in this type of hazardous

(classified) area.

The Exception allows Type MC cables to be

installed in Class II, Division 1 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.

502.4. Wiring Methods. (B) Class II, Division 2

(Combustible Dusts).

This section states:

Type ITC and PLTC cables may be installed in

ladder or ventilated cable trays following the same

practices as used in non-hazardous (unclassified)

areas. No spacing is required between the ITC or

PLTC cables. This is logical as the ITC and PLTC

cable circuits are all low energy circuits which do not

produce any significant heat or heat dissipation

problems.

Type MC, MI and TC [See Section 336.4(3)] cables

may be installed in ladder, ventilated trough, or

ventilated cable channel, but they are not allowed to

be installed in solid bottom cable trays.

Required Spacing in Cable Trays for Type MC, MI & TC

Cables in Class II, Division 2 Hazardous (Classified) Areas

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Cooper B-Line, Inc Cable Tray Manual

D1 D1 D2 D2 D3

D2 D1 D1 D1

Note 1. The cables are limited to a single layer

with spacing between cables equal to the diameter

of the largest adjacent cable. This means that the

cables must be tied down at frequent intervals in

horizontal as well as vertical cable trays to maintain

the cable spacing. A reasonable distance between

ties in the horizontal cable tray would be

approximately 6 feet (See Section 392.8 Cable

Installation - Tying cables to cable trays).

Note 2. Spacing the cables a minimum of 1 inch

from the side rails to prevent dust buildup is

recommended. This is not an NEC requirement but

a recommended practice.

Where cable tray wiring systems with current

carrying conductors are installed in a dust

environment, ladder type cable trays should be used

since there is less surface area for dust buildup than

in ventilated trough cable trays. The spacing of the

cables in dust areas will prevent the cables from

being totally covered with a solid dust layer. In dusty

areas, the top surfaces of all equipment, raceways,

supports, or cable jacket surfaces where dust layers

can accumulate will require cleanup housekeeping at

certain time intervals. Good housekeeping is

required for personnel health, personnel safety and

facility safety. Excessive amounts of dust on

raceways or cables will act as a thermal barrier

which may not allow the power and lighting

insulated conductors in a raceway or cable to safely

dissipate internal heat. This condition may result in

the accelerated aging of the conductor insulation. A

cable tray system that is properly installed and

maintained will provide a safe dependable wiring

system in dust environments.

Exception: Type MC cable listed for use in Class

II,Division I locations shall be permitted to be

installed without the above spacing limitations. This

was a new exception for the 1999 NEC®code.

For this type of wiring there is no danger of the

cables being overheated when covered with dust.

The current flow in these circuits is so low that the

internally generated heat is insufficient to heat the

cables and cable spacing is not a necessity. Even

under such conditions, layers of dust should not be

allowed to accumulate to critical depths as they may

be ignited or explode as the result of problems

caused by other than the electrical system.

502.4(B)(3). Nonincendive Field Wiring

Wiring in nonincendive circuits shall be permitted

using any of the wiring methods suitable for wiring

in ordinary locations.

503.3. Wiring Methods. (A) Class III, Division 1

and (B) Class III, Division 2 (Ignitable Fibers or

Flyings). Type MI or MC cables may be installed in

cable tray in these types of hazardous (classified)

areas. The installations should be made using

practices that minimize the build-up of materials in

the trays. This can be done by using ladder cable

tray with a minimum spacing between the cables

equal to the diameter of the largest adjacent cable.

In some cases, a greater spacing between cables

than that based on the cable diameters might be

desirable depending on the characteristics of the

material that requires the area to be classified. Here

again, it must be emphasized that good

housekeeping practices are required for all types of

wiring systems to insure the safety of the personnel

and the facility.

504.20. Wiring Methods. This section allows

intrinsically safe wiring systems to be installed in

cable trays in hazardous (classified) areas. Section

504.30 specifies the installation requirements for

intrinsically safe wiring systems that are installed in

cable trays. Section 504.70 specifies the sealing

requirements for cables that may be part of a cable

tray wiring system. Section 504.80(B) states that

cable trays containing intrinsically safe wiring must

be identified with permanently affixed labels.

Cable trays are ideal for supporting both

intrinsically safe and nonintrinsically safe cable

systems as the cables may be easily spaced and tied

in position or a standard metallic barrier strip may

be installed between the intrinsically and

nonintrinsically safe circuits.

505.15. Wiring Methods. This section was

added to the 2002 NEC®to explicitly permit cable

trays in hazardous areas classified by the

international zone system, if the cables comply with

the cable requirements for zone locations.

392.3. Uses Permitted. (E) Nonmetallic

Cable Tray.

There are limited numbers of applications where

nonmetallic cable trays might be preferred over

metallic cable trays for electrical safety reasons

and/or for some corrosive conditions. An example

of an electrical safety application would be in an

electrolytic cell room. Here, the amperages are very

high and significant stray current paths are present.

Under such conditions, there is the possibility for a

17

Cable Tray Manual Cooper B-Line, Inc

high amperage short circuit if a low resistance

metallic path (metallic cable tray or metallic raceway)

is present [See information under Section 392.5(F)

Nonmetallic Cable Trays].

392.4. Uses Not Permitted.

This is the only place in the NEC®where all the

various types of cable tray have limitations on their

place of use. No cable trays can be used in

hoistways or where subject to severe physical

damage. The designer must identify the zones of

installation where a cable tray might be subjected to

severe physical damage. Usually such areas are

limited and provisions can be made to protect the

cable tray by relocating it to a more desirable

location or as a last resort to provide protection

using the appropriate structural members.

The second sentence of Section 392.4 states that

cable tray shall not be used in environmental air

spaces except to support the wiring methods

recognized for use in such spaces. This is not a

restriction on cable tray as long as it is used as a

support for the appropriate cable types.

Metallic cable trays may support cable types

approved for installation in Ducts or Plenums Used

for Environmental Air as per Section 300.22(B) and

the cable types approved for installation in Other

Space Used for Environmental Air as per Section

300.22(C).

The second sentence of Section 300.22(C)(1) is as

follows:

Other types of cables and conductors shall

be installed in electrical metallic tubing,

flexible metallic tubing, intermediate metal

conduit, rigid metal conduit without an

overall nonmetallic covering, flexible metal

conduit, or, where accessible, surface metal

raceway or metal wireway with metal covers

or solid bottom metal cable tray with solid

metal covers.

Reprinted with permission from NFPA 70-1999, the National Electrical Code®,

Copyright© 1998, National Fire Protection Association, Quincy, MA 02269. This reprinted

material is not the complete and official position of the National Fire Protection Association,

on the referenced subject which is represented only by the standard in its entirety.

This part of Section 300.22(C) is confusing. The

statement as underlined in the above paragraph

leads some to assume, for installations in Other

Spaces Used for Environmental Air, that the types

of insulated single conductors which are installed in

raceway installations may also be installed in solid

bottom metal cable trays with metal covers. This is

not so. Only the appropriate multiconductor cable

types as per Section 392.3(A) may be installed in

solid bottom cable trays.

Cable tray may be used to support data process

wiring systems in air handling areas below raised

floors as per Sections 300.22(D) and 800.52(D).

392.5. Construction Specifications. (A)

Strength and Rigidity.

The designer must properly select a structurally

satisfactory cable tray for their installation. This

selection is based on the cable tray's strength, the

cable tray loading and the spacing of the supports.

The NEMA Metallic Cable Tray Systems Standard

Publication VE-1 contains the cable tray selection

information and it is duplicated in B-Line's Cable

Tray Systems Catalog.

The NEMA Standard provides for a static load

safety factor of 1.5. A number (Span in Feet - the

distance between supports) and letter (Load in lbs/ft)

designation is used to properly identify the cable

tray class on drawings, in specifications, in quotation

requisitions, and in purchase requisitions to

guarantee that the cable tray with the proper

characteristics will be received and installed. The

designer must specify the cable tray type, the

material of construction, section lengths, minimum

bend radius, width, rung spacing (for a ladder type

cable tray), and the total loading per foot for the

cables on a maximum support spacing (See page 52

for cable tray specifications checklist). For many

installations, the cable trays must be selected so that

they are capable of supporting specific concentrated

loads, the weight of any equipment or materials

attached to the cable tray, ice and snow loading,

and for some installations the impact of wind

loading and/or earthquakes must be considered.

Most cable trays are utilized as continuous beams

with distributed and concentrated loads. Cable trays

can be subjected to static loads like cable loads and

dynamic loads such as wind, snow, ice, and even

earthquakes. The total normal and abnormal loading

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Cooper B-Line, Inc Cable Tray Manual

for the cable tray is determined by adding all the

applicable component loads. The cable load + the

concentrated static loads + ice load (if applicable) +

snow load (if applicable) + wind load (if applicable) +

any other logical special condition loads that might

exist. This total load is used in the selection of the

cable tray.

The following is an explanation of the

‘historical’ NEMA cable tray load

classifications found in NEMA VE-1.

There used to be four cable tray support span

categories, 8, 12, 16, and 20 feet, which are

coupled with one of three load designations, "A" for

50 lbs/ft, "B" for 75 lbs/ft, and "C" for 100 lbs/ft.

For example, a NEMA class designation of 20B

identifies a cable tray that is to be supported at a

maximum of every 20 feet and can support a static

load of up to 75 lbs/linear foot.

The cable load per foot is easy to calculate using

the cable manufacturer's literature. If the cable tray

has space available for future cable additions, a

cable tray has to be specified that is capable of

supporting the final future load. Although these

historical load designations are still useful in

narrowing down the choices of cable trays, NEMA

has recently changed the VE-1 document. NEMA

VE-1 now requires the marking on the cable trays to

indicate the exact rated load on a particular span.

Trays are no longer limited to the four spans and

three loads listed above. Now, for example, a tray

may be rated for 150 lbs/ft on a 30 ft. span. It is

recommended when specifying cable tray, to specify

the required load, support span and straight section

length to best match the installation.

Example of Cable Loading per foot:

10 - 3/C No. 4/0 (2.62 lbs/ft)

Total = 26.20 lbs/ft

3 - 3/C No. 250 kcmil (3.18 lbs/ft)

Total = 9.54 lbs/ft

4 - 3/C No. 500 kcmil (5.87 lbs/ft)

Total = 23.48 lbs/ft

Total Weight of the Cables = 59.22 lbs/ft

These cables would fill a 30 inch wide cable tray

and if a 36 inch wide cable tray were used there

would be space available for future cables (See pages

47 thru 53 for information on calculating tray width.). To

calculate the proper cable tray design load for the

36" wide cable tray multiply 59.22 lbs/ft x 36

inches/30 inches = 71.06 lbs/ft. If this cable tray is

installed indoors, a load symbol "B" cable tray would

be adequate. If there were additional loads on the

cable tray or the cable tray were installed outdoors,

it would be necessary to calculate all the additional

potential loads. The potential load most often

ignored is installation loads. The stresses of pulling

large cables through cable trays can produce 3 times

the stress of the cables' static load. If the installation

load is not evaluated the cable tray may be damaged

during installation. A 16C or 20C NEMA Class

should be specified if large cables are to be pulled.

Even though walking on cable tray is not

recommended by cable tray manufacturers and

OSHA regulations, many designers will want to

specify a cable tray which can support a 200 lb.

concentrated load "just in case". A concentrated

static load applied at the midspan of a cable tray is

one of the most stressful conditions a cable tray will

experience. To convert a static concentrated load at

midspan to an equivalent distributed load take twice

the concentrated load and divide it by the support

span [(2 x 200 lbs.)/Span]. The strength of the rung

is also a very important consideration when

specifying a concentrated load. The rung must be

able to withstand the load for any tray width, as well

as additional stresses from cable installation.

Excessive rung deflection can weaken the entire

cable tray system. B-Line uses heavier rungs on

their wider industrial trays as a standard. Most cable

tray manufacturer's rungs are not heavy enough to

withstand concentrated loads at 36" tray widths.

For outdoor installations a cable tray might be

subject to ice, snow, and wind loading. Section 25

of the National Electrical Safety Code (published by

the Institute of Electrical and Electronic Engineers)

contains a weather loading map of the United States

to determine whether the installation is in a light,

medium, or heavy weather load district. NESC Table

250-1 indicates potential ice thicknesses in each

loading district as follows: 0.50 inches for a heavy

loading district, 0.25 inches for a medium loading

district, and no ice for a light loading district. To

calculate the ice load use 57 pounds per cubic foot

for the density of glaze ice. Since tray cables are

circular and the cable tray has an irregular surface

the resulting ice load on a cable tray can be 1.5 to

2.0 times greater than the glaze ice load on a flat

surface.

Snow load is significant for a cable tray that is

completely full of cables or a cable tray that has

covers. The density of snow varies greatly due to its

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Cable Tray Manual Cooper B-Line, Inc

moisture content, however the minimum density

that should be used for snow is 5 pounds per cubic

foot. The engineer will have to contact the weather

service to determine the potential snow falls for the

installation area or consult the local building code

for a recommended design load.

Usually cable trays are installed within structures

such that the structure and equipment shelter the

cable trays from the direct impact of high winds. If

wind loading is a potential problem, a structural

engineer and/or the potential cable tray

manufacturer should review the installation for

adequacy. To determine the wind speed for proper

design consult the Basic Wind Speed Map of the

United States in the NESC (Figure 250-2).

For those installations located in earthquake areas,

design engineers can obtain behavioral data for

B-Line cable trays under horizontal, vertical and

longitudinal loading conditions. Testing done for

nuclear power plants in the 1970's indicates that

cable trays act like large trusses when loaded

laterally and are actually stronger than when loaded

vertically. Cable tray supports may still need to be

seismically braced and designers should consult the

B-Line Seismic Restraints Catalog for detailed

design information.

The midspan deflection multipliers for all B-Line

cable trays are listed in the Cable Tray Systems

catalog. Simply pick your support span and multiply

your actual load by the deflection multiplier shown

for that span. The calculated deflections are for

simple beam installations at your specified load

capacity. If a deflection requirement will be

specified, extra care needs to be taken to ensure

that it does not conflict with the load requirement

and provides the aesthetics necessary. Keep in mind

that continuous beam applications are more

common and will decrease the deflection values

shown by up to 50%. Also, aluminum cable trays

will deflect 3 times more than steel cable trays of the

same NEMA class.

To complete the design, the standard straight

section length and minimum bend radius must be

chosen. When selecting the recommended length of

straight sections, be sure that the standard length is

greater than or equal to the maximum support span.

Choose a fitting radius which will not only meet or

exceed the minimum bend radius of the cables but

will facilitate cable installation.

[See page 11 for more information on selecting the

appropriate cable tray length]

392.5. Construction Specifications. (B)

Smooth Edges.

This is a quality statement for cable tray systems

and their construction. B-Line cable tray is designed

and manufactured to the highest standards to

provide easy, safe installation of both the cable tray

and cables.

392.5. Construction Specifications. (C)

Corrosion Protection.

Cable tray shall be protected from corrosion per

Section 300.6, which lists some minimum criteria

for different corrosive environments. The B-Line

Cable Tray Catalog contains a corrosion chart for

cable tray materials. Cable trays may be obtained in

a wide range of materials including aluminum,

pregalvanized steel, hot dipped galvanized steel

(after fabrication), Type 304 or 316 stainless steel,

polyvinyl chloride (PVC) or epoxy coated aluminum

or steel and also nonmetallic (fiber reinforced

plastic). Check with a metallurgist to determine

which metals and coatings are compatible with a

particular corrosive environment. B-Line has

corrosion information available and may be able to

recommend a suitable material. Remember that no

material is totally impervious to corrosion. Stainless

steel can deteriorate when attacked by certain

chemicals and nonmetallic cable trays can

deteriorate when attacked by certain solvents.

392.5. Construction Specifications. (D) Side

Rails.

The technical information in Article 392 was

originally developed for cable trays with rigid side

rails by the 1973 NEC®Technical Subcommittee

on Cable Tray. “Equivalent Structural Members” was

added later to incorporate new styles of cable tray

such as center rail type tray and ‘mesh’ or wire

basket tray.

392.5. Construction Specifications. (E)

Fittings.

This section has been misinterpreted to mean that

cable tray fittings must be used for all changes in

direction and elevation [See Section 392.6(A) Complete

system for further explanation). When two cable tray

runs cross at different elevations, lacing a cable

between the rungs of one tray and dropping into the

other is a common practice which changes the

direction of the cable while providing adequate cable

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Cooper B-Line, Inc Cable Tray Manual

support. Although the use of cable tray fittings is not

mandatory, it is often desirable to use them when

possible to improve the appearance of the

installation.

392.5. Construction Specifications. (F)

Nonmetallic Cable Tray.

This type of cable tray is usually made of

Fiberglass Reinforced Plastic (FRP). Applications for

FRP cable tray systems include some corrosive

atmospheres and where non-conductive material is

required. B-Line fiberglass cable tray systems are

manufactured from glass fiber reinforced plastic

shapes that meet ASTM flammability and self-

extinguishing requirements. A surface veil is applied

during pultrusion to ensure a resin rich surface and

increase ultraviolet resistance, however, for extended

exposure to direct sunlight, additional measures,

such as painting the tray, are sometimes employed

to insure the longevity of the product. Ambient

temperature is also a design consideration when

FRP cable tray is used. An ambient temperature of

100°F will decrease the loading capacity of poltester

resin fiberglass cable tray by 10%.

392.6. Installation. (A) Complete System.

This section states that cable tray systems can

have mechanically discontinuous segments, and that

the mechanically discontinuous segment cannot be

greater than 6 feet. A bonding jumper sized per

Section 250.102 is necessary to connect across any

discontinuous segment. The bonding of the system

should be in compliance with Section 250.96.

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Cable Tray Manual Cooper B-Line, Inc

Nomenclature

1. Ladder Type Cable Tray 10. 30° Vertical Inside Bend, Ladder Type Tray

2. Ventilated Trough Type Cable Tray 11. Vertical Bend Segment (VBS)

3. Splice Plate 12. Vertical Tee Down, Ventilated Trough Type Tray

4. 90° Horizontal Bend, Ladder Type Tray 13. Left Hand Reducer, Ladder Type Tray

5. 45° Horizontal Bend, Ladder Type Tray 14. Frame Type Box Connector

6. Horizontal Tee, Ladder Type Tray 15. Barrier Strip Straight Section

7. Horizontal Cross, Ladder Type Tray 16. Solid Flanged Tray Cover

8. 90° Vertical Outside Bend, Ladder Type Tray 17. Cable Channel Straight Section, Ventilated

9. 45° Vertical Outside Bend, Ventilated Type Tray 18. Cable Channel, 90° Vertical Outside Bend

1

2

3

4

6

7

8

10

11 12 13

14

15

16

17

18

Typical Cable

Tray Layout

5

9

Cable Tray Elevation Change Without Fittings

Bonding

Jumper

There are some designers, engineers, and

inspectors that do not think that cable tray is a

mechanical support system just as strut is a

mechanical support system. Cable tray is not a

raceway in the NEC®but some designers, engineers,

and inspectors attempt to apply the requirements for

raceway wiring systems to cable tray wiring systems

even when they are not applicable. Cable tray wiring

systems have been used by American industry for

over 35 years with outstanding safety and continuity

of service records. The safety service record of cable

tray wiring systems in industrial facilities has been

significantly better than those of conduit wiring

systems. There have been industrial fires and

explosions that have occurred as a direct result of the

wiring system being a conduit wiring system. In these

cases, cable tray wiring systems would not have

provided the fires and explosions that the conduit

systems did by providing as explosion gas flow path

to the ignition source even though the conduit

systems contained seals.

The most significant part of this section is that the

metallic cable tray system must have electrical

continuity over its entire length and that the support

for the cables must be maintained. These

requirements can be adequately met even though

there will be installation conditions where the cable

tray is mechanically discontinuous, such as at a

firewall penetration, at an expansion gap in a long

straight cable tray run, where there is a change in

elevation of a few feet between two horizontal cable

tray sections of the same run, or where the cables

drop from an overhead cable tray to enter

equipment. In all these cases, adequate bonding

jumpers must be used to bridge the mechanical

discontinuity.

Control Cable Entering Pushbutton and

Power Cable Entering Motor Terminal Box

from 6 Inch Channel Cable Tray System

(Bottom entries provide drip loops to prevent moisture

flow into enclosures.)

Cables Exiting 480 Volt Outdoor

Switchgear and Entering Cable Tray System

(Cable fittings with clamping glands are required to prevent

moisture flow into equipment due to the cable's overhead

entry into the switchgear enclosure).

Cables Entering and Exiting Motor Control

Centers from Cable Tray Systems.

392.6. Installation. (B) Completed Before

Installation.

This means that the final cable tray system must

be in place before the cables are installed. It does

not mean that the cable tray must be 100%

mechanically continuous. The electrical bonding of

the metallic cable tray system must be complete

before any of the circuits in the cable tray system

are energized whether the cable tray system is being

utilized as the equipment grounding conductor in

qualifying installations or if the bonding is being

done to satisfy the requirements of Section 250.96.

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Cooper B-Line, Inc Cable Tray Manual

392.6. Installation. (C) Supports.

The intent of this section is to ensure that the

conductor insulation and cable jackets will not be

damaged due to stress caused by improper support.

Multiconductor 600 volt Type TC cables and 300

volt Type PLTC cables exhibit a high degree of

damage resistance when exposed to mechanical

abuse at normal temperatures.

During an inspection of industrial installations by

the 1973 NEC®Technical Subcommittee on Cable

Tray, a test setup was constructed of an 18 inch

wide Class 20C aluminum cable tray supported

three feet above ground level containing several

sizes of multiconductor cables. This installation was

continuously struck in the same area with eight

pound sledge hammers until the cable tray was

severely distorted, the cables however, exhibited

only cosmetic damage. When these cables were

tested electrically, they checked out as new tray

cable. Since that time, significant improvements

have been made in cable jacket and conductor

insulation materials so that the cables available today

are of better quality than the 1973 test cables.

Although tray cables are capable of taking a great

deal of abuse without any problems, cable tray

installations must be designed by taking appropriate

measures to ensure that the tray cables will not be

subjected to mechanical damage.

392.6. Installation. (D) Covers.

Cable tray covers provide protection for cables

where cable trays are subject to mechanical damage.

The most serious hazard to cable in cable trays is

when the cables are exposed to significant amounts

of hot metal spatter during construction or

maintenance from torch cutting of metal and

welding activities. For these exposure areas, the

cable tray should be temporarily covered with

plywood sheets. If such exposure is to be a frequent

occurrence, cable tray covers should be installed in

the potential exposure areas. Where cable trays

contain power and lighting conductors, raised or

ventilated covers are preferable to solid covers since

the raised or ventilated covers allow the cable heat

to be vented from the cable tray.

When covers are installed outdoors, they should

be attached to the cable trays with heavy duty wrap

around clamps instead of standard duty clips. During

high winds, the light duty clips are not capable of

restraining the covers. Outdoor cover installations

should be overlapped at expansion joint locations to

eliminate cover buckling. Covers which fly off the

cable tray create a serious hazard to personnel, as

was the case at a Texas gulf coast chemical plant

where operators would not leave their control room

because hurricane force winds had stripped many

light gauge stainless steel covers off a large cable

tray system. These sharp edged metal covers were

flying though the air all during the high wind period,

posing a serious threat to the worker's safety.

Types of Cable Tray Covers.

Aluminum Cable Tray Cover Accessories -

Equivalent Items are available for Steel Cable Trays.

23

Cable Tray Manual Cooper B-Line, Inc

Standard

Cover Clamp

Combination Cover

& Hold Down Clamp

Heavy Duty

Cover Clamp Cover Joint Strip

Raised

Cover Clamp

Solid Non-Flanged Solid Flanged

Ventilated Flanged

Peaked Flanged

392.6. Installation. (E) Multiconductor

Cables Rated 600 Volts or Less.

Cables containing 300 or 600 volt insulated

conductors may be installed intermingled in the

same cable tray which is different from the

requirements for raceways. This is a reasonable

arrangement because a person may safely touch a

300 or 600 volt cable which is in good condition, so

having the cables come into contact with each other

is not a problem either. Many cable tray users

separate the instrumentation cables from the power

and control cables by installing them in separate

cable trays or by installing barriers in the cable trays.

Often, because of the volume of the instrumentation

cable, using separate cable trays is the most

desirable installation practice.

Numerous cable tray systems have been installed

where the instrumentation cables and branch circuit

cables are installed in the same cable trays with and

without barriers with excellent performance and

reliability. Most problems that occur involving

instrumentation circuits are due to improper

grounding practices. For analog and digital

instrumentation circuits, good quality twisted pair

Type ITC and Type PLTC cables with a cable shield

and a shield drain wire should be used. Do not

purchase this type of cable on price alone, it should

be purchased because of it's high quality. Engineers

specifying cables should be knowledgeable of the

cable's technical details in order to design systems

which will provide trouble free operation.

392.6. Installation. (F) Cables Over 600

Volts.

Cables with insulation rated 600 volts or less may

be installed with cables rated over 600 volts if either

of the following provisions are met.

No. 1: Where the cables over 600 volts are

Type MC.

No. 2: Where separated with a fixed solid

barrier of a material compatible with the cable

tray.

392.6. Installation. (G) Through Partitions

and Walls.

Whether penetrating fire rated walls with tray cable

only or cable tray and tray cable, the designer should

review with the local building inspector the method

he proposes to use to maintain the fire rating

integrity of the wall at the penetration. Many

methods for sealing fire wall penetrations are

available, including bag or pillow, caulk,

cementitious, foam, putty and mechanical barrier

systems.

Many designers prefer to run only the tray cable

through fire rated walls. Sealing around the cables is

easier than sealing around the cables and the cable

tray. Also, should the cable tray or its supports

become damaged, the tray will not exert forces

which could damage the wall or the penetration.

392.6. Installation. (H) Exposed and

Accessible.

Article 100 - Definitions.

Exposed: (as applied to wiring methods)

on or attached to the surface or behind

panels designed to allow access.

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Cooper B-Line, Inc Cable Tray Manual

300 & 600

Volt Cables Fixed Solid Barrier

Comparable Material Cables Rated

Over 600 Volts

NO. 2

300 & 600

Volt Cables Cables Rated Over

600 Volts Are Type MC

NO. 1

Accessible: (As applied to wiring methods)

Capable of being removed or exposed

without damaging the building structure or

finish, or not permanently closed in by the

structure or finish of the building.

Reprinted with permission from NFPA 70-1999, the National Electrical Code®,

Copyright© 1998, National Fire Protection Association, Quincy, MA 02269. This reprinted

material is not the complete and official position of the National Fire Protection Association,

on the referenced subject which is represented only by the standard in its entirety.

392.6. Installation. (I) Adequate Access.

Cable tray wiring systems should be designed and

installed with adequate room around the cable tray

to allow for the set up of cable pulling equipment.

Also, space around the cable tray provides easy

access for installation of additional cables or the

removal of surplus cables. Where cable trays are

mounted one above the other, a good rule to follow

is to allow 12 to 18 inches between the underside

and the top of adjacent cable trays or between the

structure's ceiling and the top of the cable tray.

392.6. Installation. (J) Conduits and

Cables Supported from Cable Tray.

For the 1996 NEC®, a significant change was

made in this section. The installations covered in

this section may now only be made in qualifying

industrial facilities.

In Section 392.6(J) of the 1993 NEC®, cable tray

installations that supplied support for conduits were

not restricted to qualifying industrial facilities. The

1996 NEC®, Section 392.6(J) text restricts the use

of such installations even though there is no

documented history of problems in non-industrial

installations.

As a result of the change in this section, identical

functional installations in non-qualifying installations

(commercial and industrial) and qualifying industrial

installations have different physical requirements. In

a qualifying industrial installation, a conduit

terminated on a cable tray may be supported from

the cable tray. In a commercial or non-qualifying

industrial installation, the conduit that is terminated

on the cable tray must be securely fastened to a

support that is within 3 feet of the cable tray or

securely fastened to a support that is within 5 feet of

the cable tray where structural members don’t

readily permit a secure fastening within 3 feet. The

conduit of the non-qualifying installation still needs

to be bonded to the cable tray. A fitting may be used

for this bonding even though it will not count as a

mechanical support.

Over 99 percent of the conduits supported on

cable trays are the result of conduits being

terminated on the cable tray side rails [See Section

392.8(C)]. For over 40 years, it has been common

practice to house the cables exiting the cable tray in

conduits or cable channel where the distance from

the cable tray system to the cable terminations

requires the cable be supported. Several

manufacturers supply UL approved cable tray to

conduit clamps such as the B-Line 9ZN-1158.

In addition to conduit and cables being supported

from cable tray; industrial companies have been

mounting instrumentation devices, push buttons, etc.

on cable tray and cable channel for over 40 years.

This section once lead some to believe that only

conduit or cables may be supported from cable trays

which is not correct as cable tray is a mechanical

support just as strut is a mechanical support.

Because of this, the wording in Section 392.6(J) of

the 2002 NEC®was changed. Instead of allowing

only cable and conduit to be supported from cable

tray, the code now states that raceways, cables,

boxes and conduit bodies are now permitted to

be supported from the cable tray. Where boxes or

conduit bodies are attached to the bottom or side of

the cable tray, they must be fastened and supported

in accordance with Section 314.23.

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Cable Tray Manual Cooper B-Line, Inc

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Cooper B-Line, Inc Cable Tray Manual

UL Listed Conduit To

Cable Tray Clamp

See NEC®Table 344.30(B)(2) To Obtain The

Support Requirements For Other Conduit Sizes.

Conduit Terminated On And Supported By The Cable Tray Side Rail.

Installation For Qualifying Industrial Facilities As Per 392.6(J).

16 Feet

2 Inch Rigid Metal Conduit

Position Of The First

Conduit Support

From The Cable Tray

(Conduit Must Be

Securely Fastened To

The Support)

Conduit Bushing

Cable Tray

Side Rail

Cable Tray

UL Listed Conduit To

Cable Tray Clamp

See Section 344.30

Conduit Terminated On The Cable Tray Side Rail.

Installation For Commercial And Non-Qualifying Industrial Facilities As Per 392.6(J).

3 Feet or 5 Feet

Any Size Of Rigid Metal Conduit

Position Of The First

Conduit Support

From The Cable Tray

(Conduit Must Be

Securely Fastened To

The Support)

Conduit Bushing

Cable Tray

Side Rail

Cable Tray

392.7. Grounding. (A) Metallic Cable

Trays.

All metallic cable trays shall be grounded as

required in Article 250 regardless of whether or not

the cable tray is being used as an equipment

grounding conductor (EGC).

The EGC is the most important conductor in an

electrical system as its function is electrical safety.

There are three wiring options for providing an

EGC in a cable tray wiring system: (1) An EGC

conductor in or on the cable tray. (2) Each

multiconductor cable with its individual EGC

conductor. (3) The cable tray itself is used as the

EGC in qualifying facilities.

27

Cable Tray Manual Cooper B-Line, Inc

Ground Bus

Bonded To

Enclosure

EGC

EGC In

Cable

Discontinuous Joints

Require Bonding

For Qualifying Facilities

EGCs in the Cables or

EGC Cables Are Not

Required If Rating Of The

Feeder Overcurrent Device

Permits Using The Tray

For the EGC

Bonding Jumper Not

Required For Rigidly

Bolted Joints

Conduit

Three Phase

Motor Installation

Building Steel

Lightning

Protection

Grounding

Bond

Switchgear

Bond

System Ground

Transformer

(Solidly

Grounded

Secondary)

Motor Control Center

Correct Bonding Practices To Assure That The

Cable Tray System Is Properly Grounded

If an EGC cable is installed in or on a cable tray, it should be bonded to each or alternate cable

tray sections via grounding clamps (this is not required by the NEC®but it is a desirable practice). In

addition to providing an electrical connection between the cable tray sections and the EGC, the

grounding clamp mechanically anchors the EGC to the cable tray so that under fault current

conditions the magnetic forces do not throw the EGC out of the cable tray.

A bare copper equipment grounding conductor should not be placed in an aluminum cable tray

due to the potential for electrolytic corrosion of the aluminum cable tray in a moist environment.

For such installations, it is best to use an insulated conductor and to remove the insulation where

bonding connections are made to the cable tray, raceways, equipment enclosures, etc. with tin or

zinc plated connectors.

See Table 250.122 on page 51

for the minimum size EGC for

grounding raceway and equipment.

28

Cooper B-Line, Inc Cable Tray Manual

392.7. Grounding. (B) Steel or Aluminum

Cable Tray Systems. (1) & (2)

Reprinted with permission from NFPA 70-1999, the National Electrical Code®,

Copyright© 1998, National Fire Protection Association, Quincy, MA 02269. This reprinted

material is not the complete and official position of the National Fire Protection Association,

on the referenced subject which is represented only by the standard in its entirety.

Table 392.7(B) "Metal Area Requirements for

Cable Trays used as Equipment Grounding

Conductors" shows the minimum cross-sectional

area of cable tray side rails (total of both side rails)

required for the cable tray to be used as the

Equipment Grounding Conductor (EGC) for a

specific Fuse Rating, Circuit Breaker Ampere Trip

Rating or Circuit Breaker Ground Fault Protective

Relay Trip Setting. These are the actual trip settings

for the circuit breakers and not the maximum

permissible trip settings which in many cases are the

same as the circuit breaker frame size. If the

maximum ampere rating of the cable tray is not

sufficient for the protective device to be used, the

cable tray cannot be used as the EGC and a

separate EGC must be included within each cable

assembly or a separate EGC has to be installed in or

attached to the cable tray. [See also Section 250-

120 for additional information]

The subject of using cable tray for equipment

grounding conductors was thoroughly investigated

by the 1973 NEC®Technical Subcommittee on

Cable Tray. Many calculations were made and a

number of tests were performed by Monsanto

Company Engineers at the Bussman High Current

Laboratory. The test setup to verify the capability of

cable tray to be used as the EGC is shown in Figure

1 on page 29. The test amperes available were

forced through one cable tray side rail which had

three splice connections in series. No conductive

joint compound was used at the connections and the

bolts were wrench tight. Copper jumper cables were

used from the current source to the cable tray. The

cable tray was NEMA Class 12B. The test results

are shown on Page 45 (Appendix Sheet 1), Table I

for aluminum and Table II for steel cable tray.

One of the most interesting results of the tests was

for an aluminum cable tray with a corroded joint and

only two nylon bolts. 34,600 amperes for 14 cycles

produced only a 34° C temperature rise at the splice

plate area. If the protective devices work properly,

the temperature rises recorded at the cable tray

splices during these tests would not be sufficient to

damage the cables in the cable tray. Also note that

in these tests only one side rail was used, but in a

regular installation, both side rails would conduct

fault current and the temperature rise at the splice

plate areas would be even lower.

When the cable tray is used as the EGC,

consideration has to be given to the conduit or

ventilated channel cable tray connections to the

cable tray so that the electrical grounding continuity

is maintained from the cable tray to the equipment

utilizing the electricity. Conduit connections to the

cable tray were also tested. At that time, no

commercial fittings for connecting conduit to cable

tray were available, so right angle beam clamps

were used with very good results. There are now UL

Listed fittings for connecting and bonding conduit to

cable tray. This test setup and results are shown on

page 46 (Appendix Sheet 2).

Table 392.7(B).

Metal Area Requirements for Cable Trays

Used as Equipment Grounding Conductors

Maximum Fuse Ampere Rating,

Circuit Breaker Ampere Trip Minimum Cross-Sectional Area

Setting, or Circuit Breaker of Metal* In Square Inches

Protective Relay Ampere Trip

Setting for Ground-Fault

Protection of Any Cable Circuit Steel Aluminum

In the Cable Tray System Cable Trays Cable Trays

60 0.20 0.20

100 0.40 0.20

200 0.70 0.20

400 1.00 0.40

600 1.50** 0.40

1000 --- 0.60

1200 --- 1.00

1600 --- 1.50

2000 --- 2.00**

For SI units: one square inch = 645 square millimeters.

*Total cross-sectional area of both side rails for ladder or

trough cable trays; or the minimum cross-sectional area of

metal in channel cable trays or cable trays of one-piece

construction.

**Steel cable trays shall not be used as equipment grounding

conductors for circuits with ground-fault protection above 600

amperes. Aluminum cable trays shall not be used as equipment

grounding conductors for circuits with ground-fault protection

above 2000 amperes.

29

Cable Tray Manual Cooper B-Line, Inc

Material Thickness: 0.125" Aluminum or 14 Gauge Steel Cross Section Area,

2 Rails:

Aluminum - 1.00 sq. in.

Steel - 0.76 sq. in.

13/16"

3/8"

0.080" Aluminum or

14 Gauge Steel

3/8" Bolting Hardware

Cross Section Cable

Tray Side Rail

Adjustable Vertical

Rigid

Cable Tray Connectors

41/2"

91/2"

4"

4"

Figure 1

(See Page 45 Appendix Sheet 1)

Temperature Rise Test

C1

T T T

C2 C3

Current Source

500 kcmil copper, Type RH Insulation

Insulated Joints

Cable Lug

Fuse (if used)

Cable Lug

T - Temperature Measurement at each Tray Connection C1,

C2, & C3 - Cable Tray Connectors or Bonding Jumpers

392.7. Grounding. (B) Steel or Aluminum

Cable Tray Systems. (3) & (4)

For a cable tray to be used as an EGC the

manufacturer must provide a label showing the

cross-sectional area available. This also holds true

for some mechanically constructed cable tray

systems such as Redi-Rail®. Redi-Rail has been

tested and UL Classified as an EGC. B-Line's label is

shown at the top of page 30.

The cable tray system must be electrically

continuous whether or not it is going to serve as the

EGC. At certain locations (expansion joints,

discontinuities, most horizontal adjustable splice

plates, etc.), bonding jumpers will be required.

Section 250.96. Bonding Other Enclosures states

that cable tray shall be effectively bonded where

necessary to assure electrical continuity and to

provide the capacity to conduct safely any fault

current likely to be imposed on them (also see Sections

250.92(A)(1) & 250.118(12)).

It is not necessary to install bonding jumpers at

standard splice plate connections. The splice

connection is UL classified as an EGC component

of the cable tray system.

NOTE: The NEC®only recognizes aluminum and

steel cable trays as EGC’s. As with all metallic cable

trays, stainless steel cable trays must be bonded

according to NEC® guidelines. Fiberglass cable

trays do not require bonding jumpers since fiberglass

is non-conductive.

99-N1

600 amps max.

99-40

1600 amps max.

99-1620

2000 amps max.

30

Cooper B-Line, Inc Cable Tray Manual

Cable Tray Label

392.8. Cable Installation. (A) Cable

Splices.

There is no safety problem due to cable splices

being made in cable trays if quality splicing kits are

used, provided that the splice kits do not project

above the siderails and that they are accessible. A

box or fitting is not required for a cable splice in a

cable tray

392.8. Cable Installation. (B) Fastened

Securely.

There is no safety or technical reason to tie down

multiconductor cables in horizontal cable tray runs

unless the cable spacing needs to be maintained or

the cables need to be confined to a specific location

in the cable tray. In non-horizontal cable tray runs,

small multiconductor cables should be tied down at

3 or 4 foot intervals and larger (1 inch diameter and

above) Type MC and Type TC multiconductor

cables should be tied down at 6 foot intervals. If

used outdoors, plastic ties should be sunlight,

ultraviolet (UV), resistant and be made of a material

that is compatible with the industrial environment.

Installed outdoors, white nylon plastic ties without a

UV resistant additive will last 8 to 14 months before

breaking. Also available for these applications are

stainless steel ties and P-clamps.

(P-Clamp shown installed on industrial aluminum rung)

For single conductor cables installed in cable tray

in a single layer, each single conductor cable should

be tied to the cable tray at 6 foot intervals. Where a

circuit group of single conductors (Phase A, Phase

B, Phase C, and a Neutral if used) are bound

together with ties, the ties should be at three or four

foot intervals. In horizontal cable tray runs, the

circuit groups with ties do not have to be tied to the

cable tray. Where ties are used, they should be

made from high strength UV resistant plastic or

stainless steel. The high amperages flowing under

fault conditions in the 1/0 and larger cables

produce strong magnetic fields which result in the

conductors repelling each other until the circuit

protective device de-energizes the circuit. Under

such conditions, the cables might be forced out of

the cable tray. This happened at a northern Florida

textile plant where several hundred feet of Type MV

single conductor cable was forced out of a cable tray

run by an electrical fault because the cables were not

tied down properly.

WARNING!

Use Only As A Mechanical Support For Cables, Tubing and Raceways.

Do Not Use As A Walkway, Ladder,

Or Support For Personnel.

VENTILATED

09/05/2002

816 LIONS DRIVE

TROY, IL 62294

(618) 667-6779

Catalog Number: 24A09-12-144 STR SECTION

(and description)

Shipping Ticket: 260203 00 001

Mark Number: 78101115400

Purchase Order: D798981

Minimum Area: 1.000 SQ. IN.

Load Class: D1 179 KG/M 3 METER SPAN

REFERENCE FILE # LR360266

This product is classified by Underwriters Laboratories, Inc. as to

its suitability as an equipment grounding conductor only. 556E

30781011154005

1 of 1

392.8. Cable installation. (C) Bushed

Conduit and Tubing.

For most installations, using a conduit to cable tray

clamp for terminating conduit on cable tray is the

best method. Where a cable enters a conduit from

the cable tray, the conduit must have a bushing to

protect the cable jacket from mechanical damage; a

box is not required [See Section 300.15(C). Boxes,

Conduit Bodies, or Fittings - Where Required. Where

cables enter or exit from conduit or tubing that is

used to provide cable support or protection against

physical damage. A fitting shall be provided on the

end(s) of the conduit or tubing to protect the wires or

cables from abrasion.]. There are some special

installations where the use of conduit knockouts in

the cable tray side rail for terminating conduit is

appropriate. This would not be a good standard

practice because it is costly and labor intensive, and

if randomly used may result in damaging and

lowering the strength of the cable tray.

392.8. Cable Installation. (D) Connected

in Parallel.

Section 310.4. Conductors in Parallel. States the

following:

The paralleled conductors in each phase, neutral

or grounded conductor shall:

(1) Be the same length.

(2) Have the same conductor material.

(3) Be the same size in circular mil area.

(4) Have the same insulation type.

(5) Be terminated in the same manner.

Where run in separate raceways or cables, the

raceways or cables shall have the same physical

characteristics. Conductors of one phase, neutral, or

grounded circuit shall not be required to have the

same physical characteristics as those of another

phase, neutral, or grounded circuit conductor to

achieve balance.

A difference between parallel conductors in

raceways and those in cable trays is that the

conductors in the cable tray are not derated unless

there are more than three current carrying

conductors in a cable assembly [as per Exception

No.2 of Section 310.15(B)(2)(a) and Section

392.11(A)(1)]. Where the single conductor cables

are bundled together as per Section 392.8(D) and if

there are neutrals that are carrying currents due to

the type of load involved (harmonic currents) it may

be prudent to derate the bundled single conductor

cables .

To maintain the minimum distance between

conductors, the single conductor cables should be

securely bound in circuit groups every three or four

feet using high strength plastic or stainless steel ties.

These circuit groups provide the lowest possible

circuit reactance which is a factor in determining the

current balance among various circuit groups.

For installations that involve phase conductors of

three conductor or single conductor cables installed

in parallel, cable tray installations have conductor

cost savings advantages over conduit wiring systems.

This is because the conductors required for a cable

tray wiring system are often a smaller size than

those required for a conduit wiring system for the

same circuit. No paralleled conductor ampacity

adjustment is required for single conductor or three

conductor cables in cable trays [See NEC®Section

392.11(A)].

There were changes in the 1993 NEC®and 1996

NEC®for installations where an equipment

grounding conductor is included in a multiconductor

cable: the equipment grounding conductor must be

fully rated per Section 250.122. If multiconductor

cables with internal equipment grounding

conductors are paralleled, each multiconductor cable

must have a fully rated equipment grounding

conductor.

Section 250.122 now prohibits the use of standard

three conductor cables with standard size EGCs when

they are installed in parallel and the EGCs are

paralleled. There have been no safety or technical

31

Cable Tray Manual Cooper B-Line, Inc

Cable Channel Branch Circuit

Reprinted with permission from NFPA 70-1999, the National Electrical Code®, Copyright© 1998, National Fire

Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National

Fire Protection Association, on the referenced subject which is represented only by the standard in its entirety.

Channel to Tray

Channel to

Channel

problems due to operating standard three conductor

cables with standard sized EGCs in parallel. This has

been a standard industrial practice for over 40 years

with large numbers of such installations in service.

This change was made without any safety or

technical facts to justify this change.

To comply with Section 250.122, Three options

are available: 1. Order special cables with increased

sized EGCs which increases the cost and the

delivery time. 2. Use three conductor cables without

EGCs and install a single conductor EGC in the

cable tray or use the cable tray as the EGC in

qualifying installations. 3. Use standard cables but

don’t utilize their EGCs, use a single conductor EGC

or the cable tray as the EGC in qualifying

installations.

Should industry be required to have special cables

fabricated for such installations when there have

been absolutely no safety problems for over 40

years? Each designer and engineer must make his

own decision on this subject. If the installations are

properly designed, quality materials are used, and

quality workmanship is obtained, there is no safety

reason for not following the past proven practice of

paralleling the EGCs of standard three conductor

cable.

392.8. Cable Installation. (E) Single

Conductors.

This section states that single conductors in ladder

or ventilated trough cable tray that are Nos. 1/0

through 4/0, must be installed in a single layer.

In addition to the fill information that is in Section

392.10(A)(4), an exception was added which allows

the cables in a circuit group to be bound together

rather than have the cables installed in a flat layer.

The installation practice in the exception is desirable

to help balance the reactance’s in the circuit group.

This reduces the magnitudes of voltage unbalance in

three phase circuits.

Where ladder or ventilated trough cable trays

contain multiconductor power or lighting cables, or

any mixture of multiconductor power, lighting,

control, or signal cables, the maximum number of

cables that can be installed in a cable tray are limited

to the Table 392.9 allowable fill areas. The cable

tray fill areas are related to the cable ampacities.

Overfill of the cable tray with the conductors

operating at their maximum ampacities will result in

cable heat dissipation problems with the possibility

of conductor insulation and jacket damage.

392.9. Number of Multiconductor Cables.

Rated 2000 Volts or less, in Cable Trays.

(A) Any Mixture of Cables. (1) 4/0 or

Larger Cables

The ladder or ventilated trough cable tray must

have an inside usable width equal to or greater than

the sum of the diameters (Sd) of the cables to be

installed in it. For an example of the procedure to

use in selecting a cable tray width for the type of

cable covered in this section see page 47 (Appendix

Sheet 3), [Example 392.9(A)(1)].

Increasing the cable tray side rail depth increases

the strength of the cable tray but the greater side rail

depth does not permit an increase in cable fill area

for power or lighting cables or combinations of

power, lighting, control and signal cables. The

maximum allowable fill area for all cable tray with a

3 inch or greater loading depth side rail is limited to

the 38.9 percent fill area for a 3 inch loading depth

32

Cooper B-Line, Inc Cable Tray Manual

Compatibility Of Cable Tray Types And

Cable Trays Based On The NEC®

3", 4", & 6" Wide Solid or

Ventilated Channel Cable Tray

Solid Bottom Cable Tray

Ventilated Trough Cable Tray

Ladder Cable Tray

X - Indicates the Installations Allowed by Article 392

* - For cables rated up to 2000 volts.

** - For cables rated above 2000 volts.

*** - For 1/0 - 4/0 AWG single conductor cables

installed in ladder cable tray, maximum rung

spacing is 9 inches.

XXXX

* * *

X X X

X X X

X X X

Multiconductor Cables

300 & 600 Volt *

Single Conductor

Cables - 600 Volt *

Type MV Multiconductor

Cables **

Type MV Single Conductor

Cables **

33

Cable Tray Manual Cooper B-Line, Inc

side rail (Example: 3 inches x 6 inches inside cable

tray width x 0.389 = 7.0 square inch fill area. This

is the first value in Column 1 of Table 392.9. All

succeeding values for larger cable tray widths are

identically calculated).

392.9. Number of Multiconductor Cables.

Rated 2000 Volts or less, in Cable Trays.

(A) Any Mixture of Cable. (2) Cables

Smaller Than 4/0

The allowable fill areas for the different ladder or

ventilated trough cable tray widths are indicated in

square inches in Column 1 of Table 392.9. The

total sum of the cross-sectional areas of all the

cables to be installed in the cable tray must be equal

to or less than the cable tray allowable fill area. For

an example of the procedure to use in selecting a

cable tray width for the type of cable covered in this

section see page 48 (Appendix Sheet 4), [Example

392.9(A)(2)].

392.9. Number of Multiconductor Cables.

Rated 2000 Volts or less, in Cable Trays.

(A) Any Mixture of Cables. (3) 4/0 or

Larger Cables Installed With Cables

Smaller Than 4/0

The ladder or ventilated trough cable tray needs to

be divided into two zones (a barrier or divider is not

required but one can be used if desired) so that the

No. 4/0 and larger cables have a dedicated zone as

they are to be placed in a single layer.

The formula for this type of installation is shown

in Column 2 of Table 392.9. This formula is a trial

and error method of selecting a cable tray of the

proper width. A direct method for determining the

cable tray width is available by figuring the cable tray

widths that are required for each of the cable

combinations and then adding these widths together

to select the proper cable tray width. [Sd (sum of

the diameters of the No. 4/0 and larger cables)] +

[Sum of Total Cross Sectional Area of all Cables No.

3/0 and Smaller) x (6 inches/7 square inches)] =

The Minimum Width of Cable Tray Required. For an

example of the procedure to use in selecting a cable

tray width for the type of cable covered in this

section, see page 49, (Appendix Sheet 5), [EXAMPLE

392.9(A)(3)].

392.9. Number of Multiconductor Cables.

Rated 2000 Volts or less, in Cable Trays.

(B) Multiconductor Control and/or Signal

Cables Only.

A ladder or ventilated trough cable tray, having a

loading depth of 6 inches or less containing only

control and/or signal cables, may have 50 percent

of its cross-sectional area filled with cable. If the

cable tray has a loading depth in excess of 6 inches,

that figure cannot be used in calculating the

allowable fill area as a 6 inch depth is the maximum

value that can be used for the cross-sectional area

calculation. For an example of the procedure to use

in selecting a cable tray width for the type of cable

covered in this section, see page 50 (Appendix Sheet

6),[Example 392.9 (B)].

392.9. Number of Multiconductor Cables,

Rated 2000 Volts, Nominal, or Less, in

Cable Trays. (C) Solid Bottom Cable Trays

Containing Any Mixture.

For solid bottom cable tray, the allowable cable fill

area is reduced to approximately 30 percent as

indicated by the values in Columns 3 and 4 of Table

392.9. The first value in Column 3 was obtained as

follows: 3 in. loading depth x 6 in. inside width x

0.305 = 5.5 square inches. The other values in

Column 3 were obtained in a like manner. The Sd

term in Column 4 has a multiplier of 1 vs. the

multiplier of 1.2 for Column 2.

392.9. Number of Multiconductor Cables,

Rated 2000 Volts, Nominal, or Less, in

Cable Trays. (C) Solid Bottom Cable

Trays Containing any Mixture. (1) 4/0 or

Larger Cables

The procedure used in selecting a cable tray width

for the type of cable covered in this section is similar

to that shown on Appendix Sheet 3 page 47, but

only 90 percent of the cable tray width can be used.

34

Cooper B-Line, Inc Cable Tray Manual

392.9. Number of Multiconductor Cables,

Rated 2000 Volts, Nominal, or Less, in

Cable Trays. (C) Solid Bottom Cable

Trays Containing Any Mixture. (2) Cables

Smaller Than 4/0

The procedure used in selecting a cable tray width

for the type of cable covered in this section is similar

to that shown on Appendix Sheet 4 page 48. The

maximum allowable cable fill area is in Column 3 of

Table 392.9.

392.9. Number of Multiconductor Cables,

Rated 2000 Volts, Nominal, or Less, in

Cable Trays. (C) Solid Bottom Cable

Trays Containing any Mixture. (3) 4/0 or

Larger Cables Installed With Cables

Smaller Than 4/0

No. 4/0 and larger cables must have a dedicated

zone in the tray in order to be installed in one layer.

Therefore the cable tray needs to be divided into

two zones (a barrier or divider is not required but

one can be used if desired).

The formula for this type of installation is shown

in Column 4 of Table 392.9. This formula is a trial

and error method of selecting a cable tray of the

proper width. A direct method for determining the

cable tray width is available by figuring the cable tray

widths that are required for each of the cable

combinations and then adding these widths together

to select the proper cable tray width. [Sd (sum of the

diameters of the No. 4/0 and larger cables) x

(1.11)] + [(Sum of Total Cross-Sectional Area of all

Cables No. 3/0 and Smaller) x (6 inches/5.5

square inches) = The Minimum Width of Cable Tray

Required. The procedure used in selecting a cable

tray width for the type of cables covered in this

section is similar to that shown on Appendix Sheet

5 page 49.

392.9. Number of Multiconductor Cables,

Rated 2000 Volts, Nominal, or Less, in

Cable Trays. (D) Solid Bottom Cable Tray

Multiconductor Control and/or Signal

Cables Only.

This is the same procedure as for ladder and

ventilated trough cable trays except that the

allowable fill has been reduced from 50 percent to

40 percent. The procedure used in selecting a cable

tray width for the type of cable covered in this

section is similar to that shown on Appendix Sheet

6 page 50. [Example 392.9(B)]

392.9. Number of Multiconductor Cables,

Rated 2000 Volts, Nominal, or Less in

Cable Trays. (E) Ventilated Channel Cable

Trays.

392.9(E)(1)

Where only one multiconductor cable is installed

in a ventilated channel cable tray.

392.9(E)(2)

The fill areas for combinations of multiconductor

cables of any type installed in ventilated channel

cable tray.

392.9. Number of Multiconductor Cables,

Rated 2000 Volts, Nominal, or Less in

Cable Trays. (F) Solid Channel Cable

Trays.

392.9(F)(1)

Where only one multiconductor cable is installed

in a solid channel cable tray.

Ventilated Channel Maximum Allowable

Cable Tray Size Fill Area

3 Inch Wide 1.3 Square Inches

4 Inch Wide 2.5 Square Inches

6 Inch Wide 3.8 Square Inches

Ventilated Channel Maximum Cross-Sectional

Cable Tray Size Area of the Cable

3 Inch Wide 2.3 Square Inches

4 Inch Wide 4.5 Square Inches

6 Inch Wide 7.0 Square Inches

Solid Channel Maximum Cross-Sectional

Cable Tray Size Area of the Cable

2 Inch Wide 1.3 Square Inches

3 Inch Wide 2.0 Square Inches

4 Inch Wide 3.7 Square Inches

6 Inch Wide 5.5 Square Inches

392.9(F)(2)

The fill areas for combinations of multiconductor

cables of any type installed in solid channel cable

tray.

392.10. Number of Single Conductor

Cables, Rated 2000 Volts or Less in Cable

Trays.

Installation of single conductors in cable tray is

restricted to industrial establishments where

conditions of maintenance and supervision assure

that only qualified persons will service the installed

cable tray systems. Single conductor cables for these

installations must be 1/0 or larger, and they may

not be installed in solid bottom cable trays.

392.10. Number of Single Conductor

Cables, Rated 2000 Volts or Less in Cable

Trays. (A) Ladder or Ventilated Trough

Cable Trays. (1) 1000 KCMIL or Larger

Cables

The sum of the diameters (Sd) of all single

conductor cables shall not exceed the cable tray

width.

392.10. Number of Single Conductor

Cables, Rated 2000 Volts or Less, in

Cable Trays. (A) Ladder or Ventilated

Trough Cable Trays. (2) 250 KCMIL to

1000 KCMIL Cables

Number Of 600 Volt Single Conductor Cables

That May Be Installed In Ladder Or Ventilated

Trough Cable Tray - Section 392.10(A) (2)

392.10. Number of Single Conductor

Cables, Rated 2000 Volts or Less in Cable

Trays. (A) Ladder or Ventilated Trough

Cable Trays. (3) 1000 KCMIL or Larger

Cables Installed With Cables Smaller Than

1000 KCMIL.

Such installations are very rare.

392.10. Number of Single Conductor

Cables, Rated 2000 Volts or Less in Cable

Trays. (A) Ladder or Ventilated Trough

Cable Trays. (4) Cables 1/0 Through 4/0

The sum of the diameters (Sd) of all 1/0 through

4/0 cables shall not exceed the inside width of the

cable tray.

35

Cable Tray Manual Cooper B-Line, Inc

Dia. (Note

Single In. Area #2)

Conductor (Note) Sq. 6 9 12 18 24 30 36 42

Size #1 In. In. In. In. In. In. In. In. In.

1/0 0.58 -- 10 15 20 31 41 51 62 72

2/0 0.62 -- 9 14 19 29 38 48 58 67

3/0 0.68 -- 8 13 17 26 35 44 52 61

4/0 0.73 -- 8 12 16 24 32 41 49 57

250 Kcmil 0.84 0.55 11 18 24 35 47 59 71 82

350 Kcmil 0.94 0.69 9 14 19 28 38 47 57 65

500 Kcmil 1.07 0.90 7 11 14 22 29 36 43 50

750 Kcmil 1.28 1.29 5 8 10 15 20 25 30 35

1000 Kcmil 1.45 -- 4 6 8 12 16 20 24 28

Cable Tray Width

Notes:

#1. Cable diameter's used are those for Okonite-

Okolon 600 volt single conductor power cables.

#2. 42 inch wide is ladder cable tray only.

#3. Such installations are to be made only in qualifying

industrial facilities as per Sections 392.3(B) &

(B)(1).

#4. To avoid problems with unbalanced voltages, the

cables should be bundled with ties every three feet

or four feet. The bundle must contain the circuit's

three phase conductors plus the neutral if one is

used.

#5. The single conductor cables should be firmly tied to

the cable trays at six foot or less intervals.

Solid Channel Maximum Allowable

Cable Tray Size Fill Area

2 Inch Wide 0.8 Square Inches

3 Inch Wide 1.1 Square Inches

4 Inch Wide 2.1 Square Inches

6 Inch Wide 3.2 Square Inches

392.10. Number of Single Conductor

Cables, Rated 2000 Volts or Less in Cable

Trays. (B) Ventilated Channel Cable Trays.

The sum of the diameters (Sd) of all single

conductors shall not exceed the inside width of the

ventilated cable channel.

Number Of 600 Volt Single Conductor Cables

That May Be Installed In A Ventilated Channel

Cable Tray - Section 392.10(B)

392.11. Ampacity of Cables Rated 2000

Volts or Less in Cable Trays.

(A) Multiconductor Cables.

Ampacity Tables 310.16 and 310.18 are to be

used for multiconductor cables which are installed in

cable tray using the allowable fill areas as per Section

392.9. The ampacities in Table 310.16 are based

on an ambient temperature of 30˚ Celsius. Conduit

and cable tray wiring systems are often installed in

areas where they will be exposed to high ambient

temperatures. For such installations, some designers

and engineers neglect using the Ampacity Correction

Factors listed below the Wire Ampacity Tables which

results in the conductor insulation being operated in

excess of its maximum safe temperature. These

correction factors must be used to derate a cable for

the maximum temperature it will be subjected to

anywhere along its length.

392.11(A)(1)

Section 310.15(B)(2)(a) refers to Section 392.11

which states that the derating information of Table

310.15(B)(2)(a) applies to multiconductor cables with

more than three current carrying conductors but not

to the number of conductors in the cable tray.

392.11(A)(2)

Where cable trays are continuously covered for more

than 6 feet (1.83m) with solid unventilated covers,

not over 95 percent of the allowable ampacities of

Tables 310.16 and 310.18 shall be permitted for

multiconductor cables.

This is for multiconductor cables installed using

Table 392.16 or 392.18. If these cables are installed

in cable trays with solid unventilated covers for more

than 6 feet the cables must be derated. Where cable

tray covers are to be used, it is best to use raised or

ventilated covers so that the cables can operate in a

lower ambient temperature.

392.11(A)(3)

Where multiconductor cables are installed in a

single layer in uncovered trays, with a maintained

spacing of not less than one cable diameter between

cables, the ampacity shall not exceed the allowable

ambient temperature corrected ampacities of

multiconductor cables, with not more than three

insulated conductors rated 0-2000 volts in free air, in

accordance with Section 310.15(C).

By spacing the cables one diameter apart, the

engineer may increase the allowable ampacities of

the cables to the free air rating as per Section

310.15(C) and Table B-310.3 in Appendix B.

Notice that the allowable fill of the cable tray has

been decreased in this design due to the cable

spacing.

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Cooper B-Line, Inc Cable Tray Manual

Notes:

#1. Cable diameter's used are those for Okonite-

Okolon 600 volt single conductor power cables.

#2. Such installations are to be made only in qualifying

industrial facilities as per Sections 392.3(B) &

(B)(1).

#3. The phase, neutral, and EGCs cables are all

counted in the allowable cable fill for the ventilated

channel cable tray.

#4. To avoid problems with unbalanced voltages, the

cables should be bundled with ties every three feet

or four feet. The bundle must contain the circuit's

three phase conductors plus the neutral if one is

used. If a cable is used as the EGC, it should also

be in the cable bundle. If the designer desires, the

ventilated channel cable tray may be used as the

EGC as per Table 392.7(B)(2).

#5. The single conductor cables should be firmly tied to

the ventilated channel cable tray at six foot or less

intervals.

Single Diameter 3 Inch 4 Inch 6 Inch

Conductor Inches V. Channel V. Channel V. Channel

Size (Note #1) C.T. C.T. C.T.

1/0 AWG 0.58 5 6 10

2/0 AWG 0.62 4 6 9

3/0 AWG 0.68 4 5 8

4/0 AWG 0.73 4 5 8

250 Kcmil 0.84 3 4 7

350 Kcmil 0.94 3 4 6

500 Kcmil 1.07 2 3 5

750 Kcmil 1.28 2 3 4

1000 Kcmil 1.45 2 2 4

392.11. Ampacity of Cables Rated 2000

Volts or Less in Cable Trays. (B) Single

Conductor Cables.

Single conductor cables can be installed in a cable

tray cabled together (triplexed, quadruplexed, etc.) if

desired. Where the cables are installed according to

the requirements of Section 392.10, the ampacity

requirements are shown in the following chart as

per Section 392.11(B)(1), (2), (3), & (4):

392.12. Number of Type MV and Type

MC Cables (2001 Volts or Over) in Cable

Trays.

Sum the diameters of all the cables (Sd) to

determine the minimum required cable tray width.

Triplexing or quadruplexing the cables does not

change the required cable tray width. Whether the

cables are grouped or ungrouped, all installations

must be in a single layer.

392.13. Ampacity of Type MV and Type

MC Cables (2001 Volts or Over) in Cable

Trays. (A) Multiconductor Cables (2001

Volts or Over).

Provision No. 1: Where cable trays are

continuously covered for more than six feet

(1.83 m) with solid unventilated covers, not

more than 95% of the allowable ampacities

of Tables 310.75 and 310.76 shall be

permitted for multiconductor cables.

Cables installed in cable trays with solid

unventilated covers must be derated. Where cable

tray covers are to be used, it is best to use raised or

ventilated covers so that the cables can operate in a

lower ambient temperature.

37

Cable Tray Manual Cooper B-Line, Inc

Mult.

Solid Applicable Amp.

Sec. Cable Unventilated Ampacity Table Special

No. Sizes Cable Tray Tables Values Conditions

Cover (*) By

600 kcmil No Cover 310.17

(1) and Allowed and 0.75

Larger (**) 310.19

600 kcmil 310.17

(1) and Yes and 0.70

Larger 310.19

1/0 AWG No Cover 310.17

(2) through Allowed and 0.65

500 kcmil (**) 310.19

1/0 AWG 310.17

(2) through Yes and 0.60

500 kcmil 310.19

1/0 AWG Maintained

(3) & Larger No Cover 310.17 1.00 Spacing Of

In Single Allowed and One Cable

Layer (**) 310.19 Diameter

Single

Conductors 310.20 Spacing Of

(4) In Triangle No Cover [See NEC 2.15 x One

Config. Allowed Section 1.00 Conductor

1/0 AWG (**) 310.15(B)] O.D.

Between

and Larger Cables(***)

(*) The ambient ampacity correction factors must be used.

(**) At a specific position, where it is determined that the tray

cables require mechanical protection, a single cable tray cover of

six feet or less in length can be installed.

The wording of Section 392.11(B)(4) states that a spacing of

2.15 times one conductor diameter is to be maintained between

circuits. Two interpretations of this statement are possible.

Interpretation #1. - The 2.15 times one conductor diameter is

the distance between the centerlines of the circuits (the center

lines of the conductor bundles). Interpretation #2. - The 2.15

times one conductor diameter is the free air distance between the

adjacent cable bundles. The use of the word “circuit” is

unfortunate as its presence promotes Interpretation #1. An

installation based on Interpretation #1 is not desirable as a free

air space equal to 2.15 times one conductor diameter between

the cable bundles should be maintained to promote cable heat

dissipation.

Spacing Between Conductors

(2.15 x O.D. of Conductor)

Technically Desirable Installation

Spacing Between Conductors

(2.15 x O.D. of Conductor)

Technically Undesirable Installation

Interpretation #1

Interpretation #2

Provision No. 2: Where multiconductor

cables are installed in a single layer in

uncovered cable trays with a maintained

spacing of not less than one cable diameter

between cables, the ampacity shall not

exceed the allowable ampacities of Table

310.71 and 310.72.

If the cable tray does not have covers and the

conductors are installed in a single layer spaced not

less than one cable diameter apart, the cable

conductor ampacities can be 100 percent of the

ambient temperature corrected capacities in Tables

310.71 or 310.72.

392.13. Ampacity of Type MV and Type

MC Cables (2001 Volts or Over) in Cable

Trays. (B) Single Conductor Cables (2001

Volts or Over).

CABLE TRAY WIRING SYSTEM DESIGN

AND INSTALLATION HINTS.

Cable tray wiring systems should have a

standardized cabling strategy. Standard cable types

should be used for each circuit type. Most of the

following circuits should be included; feeder circuits,

branch circuits, control circuits, instrumentation

circuits, programmable logic controller input and

output (I/O) circuits, low level analog or digital

signals, communication circuits and alarm circuits.

Some cables may satisfy the requirements for

several circuit types. Minimizing the number of

different cables used on a project reduces installed

costs. Some companies have cable standards based

on volume usage to minimize the numbers of

different cables used on a project. For example: if a

6 conductor No. 14 control cable is needed but 7

conductor No. 14 control cable is stocked, a 7

conductor control cable would be specified and the

extra conductor would not be used. Following such a

practice can reduce the number of different cables

handled on a large project without increasing the

cost since high volume cable purchases result in cost

savings. Orderly record keeping also helps provide

quality systems with lower installation costs. The

following items should be included in the project's

cable records:

38

Cooper B-Line, Inc Cable Tray Manual

(*) The ambient ampacity correction factors must be used.

(**) At a specific position, where it is determined that the tray

cables require mechanical protection, a single cable tray cover of

six feet or less in length can be installed.

The wording of Section 392.13(B)(3) states that a spacing of

2.15 times one conductor diameter is to be maintained between

circuits. Two interpretations of this statement are possible.

Interpretation #1. - The 2.15 times one conductor diameter is

the distance between the centerlines of the circuits (the center

lines of the conductor bundles). Interpretation #2. - The 2.15

times one conductor diameter is the free air distance between the

adjacent cable bundles. The use of the word “circuit” is

unfortunate as its presence promotes Interpretation #1. An

installation based on Interpretation #1 is not desirable as a free

air space equal to 2.15 times one conductor diameter between

the cable bundles should be maintained to promote cable heat

dissipation.

Mult.

Solid Applicable Amp.

Sec. Cable Unventilated Ampacity Table Special

No. Sizes Cable Tray Tables Values Conditions

Cover (*) By

1/0 AWG No Cover 310.69

(1) and Allowed and 0.75

Larger (**) 310.70

1/0 AWG 310.69

(1) and Yes and 0.70

Larger 310.70

1/0 AWG Maintained

(2) & Larger No Cover 310.69 1.00 Spacing Of

In Single Allowed and One Cable

Layer (**) 310.70 Diameter

Single

Conductors Spacing Of

(3) In Triangle No Cover 310.67 2.15 x One

Config. Allowed and 1.00 Conductor

1/0 AWG (**) 310.68 O.D.

Between

and Larger Cables(***)

Spacing Between Conductors

(2.15 x O.D. of Conductor)

Technically Desirable Installation

Spacing Between Conductors

(2.15 x O.D. of Conductor)

Technically Undesirable Installation

Interpretation #1

Interpretation #2

39

Cable Tray Manual Cooper B-Line, Inc

•Cable Tray Tag Numbers - The tagging system

should be developed by the design personnel with

identification numbers assigned to cable tray runs on

the layout drawings. Cable tray tag numbers are

used for controlling the installation of the proper

cable tray in the correct location, routing cables

through the tray system and controlling the cable fill

area requirements.

•Cable Schedules - A wire management system

is required for any size project. Cable schedules

must be developed to keep track of the cables. This

is especially true for projects involving more than

just a few feeder cables. A typical cable schedule

would contain most or all of the following:

•The Cable Number, the Cable Manufacturer &

Catalog Number, Number of conductors, the

conductor sizes, and the approximate cable length.

•Cable Origin Location - The origin equipment

ID with the compartment or circuit number and

terminals on which the cable conductors are to be

terminated. It should also include the origin

equipment layout drawing number, and the origin

equipment connection diagram number.

•Cable Routing - Identifies the cable tray sections

or runs that a cable will occupy. Cable tray ID tag

numbers are used to track the routing.

•Cable Termination Location - The device or

terminal equipment on which the cable conductors

are to be terminated. It should also include the

termination equipment layout drawing number, and

the termination equipment connection diagram

number.

Some design consultants and corporate

engineering departments use spread sheets to

monitor the cable tray runs for cable fill. With such a

program, the cable tray fill area values for each

cable tray run or section can be continuously

upgraded. If a specified cable tray run or section

becomes overfilled, it will be flagged for corrective

action by the designer.

•Cable Installation Provisions - The cable tray

system must be designed and installed, to allow

access for cable installation. For many installations,

the cables may be hand laid into the cable trays and

no cable pulling equipment is required. There are

other installations where sufficient room must be

allotted for all the cable pulling activities and

equipment.

The cable manufacturers will provide installation

information for their cables such as maximum

pulling tension, allowable sidewall pressures,

minimum bending radii, maximum permissible

pulling length etc.. Lubricants are not normally used

on cables being installed in cable trays.

The engineer and designers should discuss in

detail the installation of the cables with the

appropriate construction personnel. This will help to

avoid installation problems and additional installation

costs. It is important that the cable pull is in the

direction that will result in the lowest tension on the

cables. Keep in mind there also needs to be room at

the ends of the pulls for the reel setups and for the

power pulling equipment. Cable pulleys should be

installed at each direction change. Triple pulleys

should be used for 90 degree horizontal bends and

all vertical bends. Single pulleys are adequate for

horizontal bends less than 90 degrees. Use rollers

in-between pulleys and every 10 to 20 feet

depending on the cable weight. Plastic jacketed

cables are easier to pull than are the metallic

jacketed cables and there is less chance of cable

damage. The pulling eye should always be attached

to the conductor material to avoid tensioning the

insulation. For interlocked armor cables, the

conductors and the armor both have to be attached

to the pulling eye.

Normally, the cables installed in cable trays are not

subjected to the damage suffered by insulated

conductors pulled into conduit. Depending on the

size of the insulated conductors and the conduit,

jamming can take place which places destructive

stresses on the cable insulation. In the October,

1991 issue of EC]&M magazine, the article on cable

pulling stated that 92 percent of the insulated

conductors that fail do so because they were

damaged in installation.

CABLE TRAY ACCESSORIES.

B-Line manufactures a full line of prefabricated

accessories for all types of B-Line cable trays. The

use of the appropriate accessories will provide

installation cost and time savings. In addition to

providing desirable electrical and mechanical

features for the cable tray system, the use of the

appropriate accessories improves the physical

appearance of the cable tray system. Some of the

most common accessories are shown below.

FIREPROOFING CABLE TRAY

Cable trays should not be encapsulated for fire

protection purposes other than for the short lengths

at fire rated walls unless the cables are adequately

derated. Encapsulation to keep fire heat out will also

keep conductor heat in. If conductors cannot

dissipate their heat, their insulation systems will

deteriorate. If the cable tray will be encapsulated,

the cable manufacturer should be consulted for

derating information.

CABLE TRAY MAINTENANCE AND

REPAIR

If the cable tray finish and load capacity is

properly specified and the tray is properly installed,

virtually no maintenance is required.

Pre-Galvanized - This finish is for dry indoor

locations. No maintenance is required.

Hot Dip Galvanized - This finish is maintenance

free for many years in all but the most severe

environments. If components have been cut or

drilled in the field, the exposed steel area should be

repaired with a cold galvanizing compound. B-Line

has a spray on zinc coating available which meets

the requirements of ASTM A780, Repair of Hot

Dip Finishes.

Aluminum - Our cable tray products are

manufactured from type 6063-T6 aluminum alloy

with a natural finish. The natural oxide finish is self

healing and requires no repair if it is field modified.

Non-metallic - Fabrication with fiberglass is

relatively easy and comparable to working with

wood. Any surface that has been drilled, cut,

sanded, or otherwise broken, must be sealed with

a comparable resin. Polyester or vinyl ester sealing

kits are available.

Cable tray should be visually inspected each year

for structural damage i.e., broken welds, bent rungs

or severely deformed side rails. If damage is evident,

from abuse or installation, it is recommended that

the damaged section of cable tray be replaced rather

than repaired. It is much easier to drop a damaged

section of tray out from under the cables than it is to

shield the cables from weld spatter.

40

Cooper B-Line, Inc Cable Tray Manual

Ladder Dropout Horizontal Adjustable

Splice

Frame Box Connector

Cable Support Fitting

Vertical Adjustable

Splice

41

Cable Tray Manual Cooper B-Line, Inc

CABLE TRAY. THERMAL CONTRACTION

AND EXPANSION

All materials expand and contract due to

temperature changes. Cable tray installations should

incorporate features which provide adequate

compensation for thermal contraction and

expansion. Installing expansion joints in the cable

tray runs only at the structure expansion joints does

not normally compensate adequately for the cable

tray's thermal contraction and expansion. The

supporting structure material and the cable tray

material will have different thermal expansion

values. They each require unique solutions to control

thermal expansion.

NEC®Section 300.7(B) states that 'Raceways

shall be provided with expansion joints where

necessary to compensate for thermal

expansion or contraction.' NEC®Section 392

does not address thermal contraction and expansion

of cable tray. One document which addresses

expansion is the NEMA Standards Publication No.

VE 2, Section 4.3.2. NEMA VE-2 Table 4-2 shows

the allowable lengths of steel and aluminum cable

tray between expansion joints for the temperature

differential values.

Reprinted with permission from NFPA 70-1999, the National Electrical Code®,

Copyright© 1998, National Fire Protection Association, Quincy, MA 02269. This reprinted

material is not the complete and official position of the National Fire Protection Association,

on the referenced subject which is represented only by the standard in its entirety.

Temp. Stainless Steel

Differential Steel Aluminum 304 316 FRP

°F (°C) Feet (m) Feet (m) Feet (m) Feet (m) Feet (m)

25 (-4) 512 (156.0) 260 (79.2) 347 (105.7) 379 (115.5) 667 (203.3)

50 (10) 256 (78.0) 130 (39.6) 174 (53.0) 189 (57.6) 333 (101.5)

75 (24) 171 (52.1) 87 (26.5) 116 (35.4) 126 (38.4) 222 (67.6)

100 (38) 128 (39.0) 65 (19.8) 87 (26.5) 95 (29.0) 167 (50.9)

125 (51) 102 (31.1) 52 (15.8) 69 (21.0) 76 (23.2) 133 (40.5)

150 (65) 85 (25.9) 43 (13.1) 58 (17.7) 63 (19.2) 111 (33.8)

175 (79) 73 (22.2) 37 (11.3) 50 (15.2) 54 (16.4) 95 (28.9)

Table 4-2

Maximum Spacing Between Expansion Joints

That Provide For One Inch (25.4 mm) Movement

For a 100°F differential (winter to summer), a steel cable tray will require an expansion

joint every 128 feet and an aluminum cable tray every 65 feet. The temperature at the

time of installation will dictate the gap setting.

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Cooper B-Line, Inc Cable Tray Manual

The Gap Setting of the Expansion Joint Splice

Plate is used as follows per the example indicated in

VE-2 Figure 4.13B.

Step 1. Plot the highest expected cable tray metal

temperature during the year on the maximum

temperature vertical axis. Example's Value: 100

Degrees F.

Step 2. Plot the lowest expected cable tray metal

temperature during the year on the minimum

temperature vertical axes. Example's Value: - 28

Degrees F.

Step 3. Draw a line between these maximum and

minimum temperature points on the two vertical

axis.

Step 4. To determine the required expansion joint

gap setting at the time of the cable tray's installation:

Plot the cable tray metal temperature at the time of

the cable tray installation on the maximum

temperature vertical axis (Example's Value: 50

Degrees F). Project over from the 50 Degrees F

point on the maximum temperature vertical axis to

an intersection with the line between the maximum

and minimum cable tray metal temperatures. From

this intersection point, project down to the gap

setting horizontal axis to find the correct gap setting

value (Example's Value: 3/8inch gap setting). This is

the length of the gap to be set between the cable

tray sections at the expansion joint.

The plotted High - Low Temperature Range in

Figure 4-13B is 128° F. The 125° F line in Table

4-1 shows that installations in these temperature

ranges would require 3/8” expansion joints

approximately every 102 feet for Steel and every

52 feet for Aluminum cable tray.

Another item essential to the operation of the

cable tray expansion splices is the type of hold down

clamps used. The cable tray must not be clamped to

each support so firmly that the cable tray cannot

contract and expand without distortion. The cable

tray needs to be anchored at the support closest to

the midpoint between the expansion joints with

hold down clamps and secured by expansion

guides at all other support locations.The expansion

guides allow the cable tray to slide back and forth as

it contracts and expands. Supports must also be

located on both sides of an expansion splice. The

supports should be located within two feet of the

expansion splice to ensure that the splice will

operate properly. If these guidelines for cable tray

thermal contraction and expansion are not followed,

there is the potential for the cable trays to tear loose

from their supports, and for the cable trays to bend

and collapse.

Max. Temp. Min. Temp.

Figure 4.13B

Gap Setting Of Expansion Splice Plate

1" (25.4 mm) Gap Maximum

130

110

90

70

50

30

10

-10

-30

50

C° F° F°

40

30

20

10

0

-10

-20

-30

-40

130

110

90

70

50

30

10

-10

-30

0

1/85/8

1/2

3/8

1/4

1

7/8

3/4

Gap Setting in Inches

Metal Temperature At Time

Of Installation (F° or C°)

As a clamp. As a guide.

1

2

3

4

43

Cable Tray Manual Cooper B-Line, Inc

44

Cooper B-Line, Inc Cable Tray Manual

Appendix Pages

Appendix Sheet 1 ........................................................................................................ 45

Temperature Rise Tests, Cable Tray Connectors, Class II

Aluminum & Steel Ladder Tray

Appendix Sheet 2 ........................................................................................................ 46

Temperature Rise Tests, Conduit Clamps For Bonding Rigid

Conduit To Cable Tray

Appendix Sheet 3 ........................................................................................................ 47

Example - NEC®Section 392.9(A)(1)

Appendix Sheet 4 ........................................................................................................ 48

Example - NEC®Section 392.9(A)(2)

Appendix Sheet 5 ........................................................................................................ 49

Example - NEC®Section 392.9(A)(3)

Appendix Sheet 6 ........................................................................................................ 50

Example - NEC®Section 392.9(B)

Appendix Sheet 7 ........................................................................................................ 51

Table 250.122 Minimum Size EGC for Raceway and Equipment

Appendix Sheet 8 ................................................................................................ 52 - 53

Cable Tray Sizing Flowchart

Appendix Sheet 9 ................................................................................................ 54 - 55

Cable Tray Installation & Specification Checklist

Appendix Sheet 10 ...................................................................................................... 56

Additional Cable Tray Resources and Engineering Software

Appendix Sheet 11 ...................................................................................................... 57

B-Line Wire Management Resources

45

Cable Tray Manual Cooper B-Line, Inc

Appendix Sheet 1

TABLE I

TEMPERATURE RISE TESTS, CABLE TRAY CONNECTORS,

CLASS II ALUMINUM LADDER CABLE TRAY

TABLE II

TEMPERATURE RISE TESTS, CABLE TRAY CONNECTORS,

CLASS II STEEL LADDER CABLE TRAY

Test Connector Data

Current Test I2TC1 C2 C3

Amps Time

And Cycles mult. Type No. & Temp. Type No. & Temp. Type No. & Temp.

Fuse by Of Type Rise Of Type Rise Of Type Rise

Size* 106Connector Bolts °C Connector Bolts °C Connector Bolts °C

1,980 52 3.4 Adj. Vert. 4 2 No. 6 CU AL-CU 10 Rigid 2 3

200A, FU 1 Bolt** Bond Lugs

1,970 394 25.5 Adj. Vert. 4 9 No. 6 CU AL-CU *** Rigid 2 15

400A, FU 1 Bolt** Bond Lugs

1,960 8100 51.8 Adj. Vert. 4 18 Rigid 4 23 Rigid 2 32

400A, FU 1 Bolt**

12,000 120 288 Adj. Vert. 4 94 Adj. Vert. 4 89 Rigid 4 81

2 Bolts** 2 Bolts**

12,000 123 295 Rigid 4 70 Rigid 4 87 Rigid 4 85

34,000 13 250 Rigid 4 71 Rigid 4 57 Rigid 4 69

Test Connector Data

Current Test I2TC1 C2 C3

Amps Time

And Cycles mult. Type No. & Temp. Type No. & Temp. Type No. & Temp.

Fuse by Of Type Rise Of Type Rise Of Type Rise

Size* 106Connector Bolts °C Connector Bolts °C Connector Bolts °C

7,900 Adj. Vert. 3/0 CU AL-CU Rigid

1,200A 66 69 1 Bolt** 4 6 Bond Lugs 18 Clean 2 8

Fuse Steel Steel

7,900 Rigid 3/0 CU AL-CU Rigid

1,200A 82 85 Corroded 4 10 Bond Lugs 22 Clean 2 9

Fuse Steel Steel

12,000 120 288 Rigid 2 50 3/0 CU AL-CU 104 Rigid 2 32

Corroded Nylon Bond Lugs Clean Steel

12,000 124 297 Rigid 4 40 Rigid 4 46 Rigid 4 21

Corroded Steel Corroded Lugs Clean Steel

34,600 14 280 Rigid 2 34 3/0 CU AL-CU 75 Rigid 2 29

Corroded Nylon Bond Lugs Clean Steel

34,400 14 276 Rigid 4 28 Rigid 4 35 Rigid 4 20

Corroded Nylon Corroded Steel Clean Steel

*Test current was interrupted in a predetermined time when a fuse was not used.

** 1 or 2 Bolts - Number of bolts installed on the adjustable vertical connector hinge.

*** The No. 6 bonding jumper melted and opened the circuit when protected by 400A fuse.

(See Page 29 - Figure 1 for Temperature Rise Test illustration)

46

Cooper B-Line, Inc Cable Tray Manual

TABLE III

TEMPERATURE RISE TESTS, CONDUIT CLAMPS

FOR BONDING RIGID CONDUIT TO CABLE TRAY

Test Test I2TRigid Conduit Cable Tray Temp.

Current Time mult. Rise Condition After Test

Amperes Cycles 106Size Material Class Material °C

36,000 16 344.7 4" Aluminum II Aluminum 19 No arcing or damage

20,900 60.5 441.2 4" Aluminum II Aluminum 70 No arcing or damage

12,100 178 433.3 4" Aluminum II Aluminum 74 No arcing or damage

21,000 20 146.8 4" Steel II Steel (?) Zinc melted at point where

conduit contacted with tray

3,260 900 159.5 4" Steel II Steel 63 No arcing or damage

21,000 30 220 2" Aluminum II Aluminum 21 No arcing or damage

12,100 120.5 294.2 2" Aluminum II Aluminum 59 No arcing or damage

8,000 245 261.1 2" Aluminum II Aluminum 44 No arcing or damage

21,000 14 103.8 2" Steel II Steel 62 Zinc melted at point where

conduit contacted with tray

12,000 60.5 145.4 2" Steel II Steel 22 Slight arc between

clamp and tray

3,240 600 104.9 2" Steel II Steel 49 No arcing or damage

21,000 20 146.8 1" Aluminum II Aluminum 20 No arcing or damage

12,200 60.5 150.3 1" Aluminum II Aluminum 24 No arcing or damage

12,100 14.5 35.3 1" Steel II Steel 6 No arcing or damage

8,000 63.5 67.84 1" Steel II Steel 59 No arcing or damage

1,980 44.5 2.9 1" Steel II Steel 1 No arcing or damage

200A FU

Appendix Sheet 2

Conduit

UL Listed

Conduit Clamp

(9ZN-1158)

Cable Tray

Conduit

Cable Tray

Right Angle

Beam Clamp To

Current

Source

To

Current

Source Conduit Clamp DetailTest Set-Up

CIRCUIT ARRANGEMENT FOR RIGID CONDUIT

TEMPERATURE RISE TESTS

47

Cable Tray Manual Cooper B-Line, Inc

Appendix Sheet 3

Example - NEC®Section 392.9(A)(1)

Width selection for cable tray containing 600 volt multiconductor cables, sizes #4/0 AWG and larger

only. Cable installation is limited to a single layer. The sum of the cable diameters (Sd) must be equal

to or less than the usable cable tray width.

Cable tray width is obtained as follows:

(D) (N) Multiply (D) x (N)

Item List List Cable List Number Subtotal of the

Number Cable Sizes Outside of Cables Sum of the Cables

Diameter Diameters (Sd)

1. 3/C - #500 kcmil 2.26 inches 4 9.04 inches

2. 3/C - #250 kcmil 1.76 inches 3 5.28 inches

3. 3/C - #4/0 AWG 1.55 inches 10 15.50 inches

The sum of the diameters (Sd) of all cables (Add Sds for items 1, 2, & 3.)

9.04 inches + 5.28 inches + 15.50 inches = 29.82 inches (Sd)

A cable tray with a usable width of 30 inches is required. For

a 10% increase in cost a 36 inch wide cable tray could be

purchased which would provide for some future cable additions.

Notes:

1. The cable sizes used in this example are a random selection.

2. Cables - copper conductors with cross linked polyethylene insulation and a PVC jacket.

(These cables could be ordered with or without an equipment grounding conductor.)

3. Total cable weight per foot for this installation.

61.4 lbs./ft. (without equipment grounding conductors)

69.9 lbs./ft. (with equipment grounding conductors)

This load can be supported by a load symbol "B" cable tray - 75 lbs./ft.

30" Usable Cable Tray Width

29.82" = Equals Cable Sd

Cross Section Of The Cables And The Cable Tray

3333333333 222 1111

48

Cooper B-Line, Inc Cable Tray Manual

Appendix Sheet 4

Example - NEC®Section 392.9(A)(2)

Width selection for cable tray containing 600 volt multiconductor cables, sizes #3/0 AWG and

smaller. Cable tray allowable fill areas are listed in Column 1 of Table 392.9.

Cable tray width is obtained as follows:

(A) (N) Multiply (A) x (N)

Item List List Cable List Total of the

Number Cable Sizes Cross Sectional Number Cross Sectional

Areas of Cables Area for Each Item

1. 3/C #12 AWG 0.17 sq. in. 20 3.40 sq. in.

2. 4/C #12 AWG 0.19 sq. in. 16 3.04 sq. in.

3. 3/C #6 AWG 0.43 sq. in. 14 6.02 sq. in.

4. 3/C #2 AWG 0.80 sq. in. 20 16.00 sq. in.

Method 1.

The sum of the total areas for items 1, 2, 3, & 4:

3.40 sq. in. + 3.04 sq. in. + 6.02 sq. in. + 16.00 sq. in. = 28.46 sq. inches

From Table 392.9 Column 1 a 30 inch wide tray with an allowable fill area of 35 sq. in.

must be used. The 30 inch cable tray has the capacity for additional future cables (6.54

sq. in. additional allowable fill area can be used.)

Method 2.

The sum of the total areas for items 1, 2, 3, & 4 multiplied by

3.40 sq. in. + 3.04 sq. in. + 6.02 sq. in. + 16.00 sq. in. = 28 46 sq. in.

Use a 30 inch wide cable tray.

Notes:

1. The cable sizes used in this example are a random selection.

2. Cables - copper conductors with cross linked polyethylene insulation and a PVC jacket.

(These cables could be ordered with or without an equipment grounding conductor.)

3. Total cable weight per foot for this installation.

31.9 lbs./ft. (Cables in this example do not contain equipment grounding conductors.)

This load can be supported by a load symbol "A" cable tray - 50 lbs./ft.

30" Usable Cable Tray Width

Cross Section Of The Cables And The Cable Tray

( )

6 in.

7 sq. in. = cable tray width required

( )

28.46 sq. in. x 6 in.

7 sq. in. = 24.39 inch cable tray width required

49

Cable Tray Manual Cooper B-Line, Inc

Example - NEC®Section 392.9(A)(3)

Width selection for cable tray containing 600 volt multiconductor cables, sizes #4/0 AWG and larger

(single layer required) and #3/0 AWG and smaller. These two groups of cables must have dedicated

areas in the cable tray.

Cable tray width is obtained as follows:

A - Width required for #4/0 AWG and larger multiconductor cables -

(D) (N) Multiply (D) x (N)

Item List List Cable List Number Subtotal of the

Number Cable Sizes Outside of Cables Sum of the Cables

Diameter Diameters (Sd)

1. 3/C - #500 kcmil 2.26 inches 3 6.78 inches

2. 3/C - #4/0 AWG 1.55 inches 4 6.20 inches

Total cable tray width required for items 1 & 2 = 6.78 inches + 6.20 inches = 12.98 inches

B - Width required for #3/0 AWG and smaller multiconductor cables -

(A) (N) Multiply (A) x (N)

Item List List Cable List Number Total of the

Number Cable Sizes Cross Sectional of Cables Cross Sectional Area

Area For Each Item

3. 3/C #12 AWG 0.17 sq. in. 20 3.40 sq. in.

4. 3/C #10 AWG 0.20 sq. in. 20 4.00 sq. in.

5. 3/C #2 AWG 0.80 sq. in. 4 3.20 sq. in.

Total cable tray width required for items 3, 4, & 5

Actual cable tray width is A - Width (12.98 in.) + B - Width (9.09 in.) = 22.07 inches

A 24 inch wide cable tray is required. The 24 inch cable tray has the capacity for additional

future cables (1.93 inches or 2.25 sq. inches allowable fill can be used).

Notes:

1. This ratio is the inside width of the cable tray in inches divided by its maximum fill area in

sq. inches from Column 1 Table 392.9.

2. The cable sizes used in this example are a random selection.

3. Cables - copper conductors with cross linked polyethylene insulation and a PVC jacket.

4. Total cable weight per foot for this installation.

40.2 lbs./ft. (Cables in this example do not contain equipment grounding conductors.)

This load can be supported by a load symbol "A" cable tray - 50 lbs./ft.

24" Usable Cable Tray Width

9.09" 1.93" 12.98"

Cross Section Of The Cables And The Cable Tray

2222 111

Appendix Sheet 5

(3.40 sq. in. + 4.00 sq. in. + 3.20 sq. in.) = (10.6 sq. in.) = 9.09 inches

( )

6 in.

7 sq. in. ( )

6 in.

7 sq. in.

1 1

50

Cooper B-Line, Inc Cable Tray Manual

Appendix Sheet 6

Example - NEC®Section 392.9(B)

Cable Tray containing Type ITC or Type PLTC Cables

50% of the cable tray useable cross sectional area can contain type PLTC cables

4 inches x 6 inches x .050 = 12 square inches allowable fill area.

2/C - #16 AWG 300 volt shielded instrumentation cable O.D. = 0.224 inches.

Cross Sectional Area = 0.04 square inches.

Notes:

1. The cable sizes used in this example are a random selection.

2. Cables - copper conductors with PVC insulation, aluminum/mylar shielding, and PVC jacket.

6" Usable Cable Tray Width

4" Usable

Cable Tray

Depth

Cross Section Of The Cables And The Cable Tray

= 300 cables can be installed in this cable tray.

12 sq. in.

0.04 sq. in./cable

= 11.54 rows can be installed in this cable tray.

300 cables

26 cables/rows

51

Cable Tray Manual Cooper B-Line, Inc

Appendix Sheet 7

Reprinted with permission from NFPA 70-1999, the National Electrical Code®, Copyright© 1998, National Fire

Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National

Fire Protection Association, on the referenced subject which is represented only by the standard in its entirety.

Table 250.122. Minimum Size Equipment Grounding

Conductors for Grounding Raceways and Equipment

Rating or Setting of Size

Automatic Overcurrent (AWG or kcmil)

Device in Circuit Ahead

of Equipment, Conduit, Aluminum or

etc., Not Exceeding Copper-Clad

(Amperes) Copper Aluminum*

15 14 12

20 12 10

30 10 8

40 10 8

60 10 8

100 8 6

200 6 4

300 4 2

400 3 1

500 2 1/0

600 1 2/0

800 1/0 3/0

1000 2/0 4/0

1200 3/0 250

1600 4/0 350

2000 250 400

2500 350 600

3000 400 600

4000 500 800

5000 700 1200

6000 800 1200

52

Cooper B-Line, Inc Cable Tray Manual

CABLE TRAY SIZING FLOWCHART

Appendix Sheet 8

392.12

W ≥Sd

(single layer)

392.3(B)(1)(a)

Not permitted

by the NEC®

392.10

Not

recognized by

the NEC®

392.10(B)

W ≥Sd 392.10(A)(1)

W ≥Sd

392.10(A)(2)

W ≥A/1.1

Note: The value “A”

only applies to cables

250 up to 1000kcmil.

The value “sd” only

applies to 1000 kcmil

and larger cables.

Note: Use when mixing

250 thru 1000 kcmil

cables with cables larger

than 1000 kcmil.

392.10(A)(3)

392.10(A)(4)

W ≥Sd

(9” max. RS)

2000V

or less

cables

Multi-

conductor

cables

S/C 1/0

or larger

Ladder

or Vented

Trough

Tray

S/C

1000

kcmil or

larger

S/C

250

kcmil up to

1000

kcmil

S/C

250 kcmil

and

larger

S/C 1/0

thru 4/0

Vented

Channel

Tray

Solid

Bottom

Tray

W ≥A/1.1 +Sd

No

No

No

No

No No No

No

Yes

Yes

Yes

Yes

YesYes Yes

Yes

Yes

Continued

on next

page

Yes

Legend

W = Cable Tray Width

D = Cable Tray Load Depth

Sd = Sum of Cable Diameters

A = Sum of Cable Areas

S/C = Single Conductor

M/C = Multiconductor Cables

RS = Ladder Rung Spacing

Start

Here

Sizing Cable Tray Per NEC 392

53

Cable Tray Manual Cooper B-Line, Inc

CABLE TRAY SIZING FLOWCHART

Appendix Sheet 8

392.9(E)(1)

W x D ≥1.6A

392.9(A)(1)

W ≥Sd

(single layer)

392.9(C)(1)

W ≥Sd/0.9

(single layer)

Note: The value “A”

only applies to cables

smaller than 4/0.

The value “Sd” only

applies to 4/0 and

larger cables, which

must be single layer

Note: The value “A”

only applies to cables

smaller than 4/0.

The value “Sd” only

applies to 4/0 and

larger cables, which

must be single layer

392.9(A)(3)

Vented

Channel

Tray

Solid

Channel

Tray

Solid

Bottom

Tray

Ladder

or Vented

Trough

Tray

One M/C

only

M/C 4/0

or larger

M/C 4/0

or larger

392.9(E)(2)

W x D ≥2.9A

392.9(F)(1)

W x D ≥1.9A

392.9(F)(2)

W x D ≥3.2A

392.9(A)(2)

W ≥A/1.2 392.9(C)(2)

W ≥A/0.9

M/C

smaller

than 4/0

One

M/C

Only

M/C

smaller

than 4/0

M/C

smaller than

4/0, with

4/0 or

larger

M/C

control

and/or

signal

W ≥A/1.2 + Sd

No NoNo

NoNo

NoNo

No No No

392.9(B)

W x D ≥2A

392.9(C)(3)

A + Sd

0.9

M/C

smaller than

4/0, with

4/0 or

larger

M/C

control

and/or

signal

W ≥

392.9(D)

W x D ≥2.5A

YesYes

Yes NoYes

Yes

Yes

Yes

YesYes

Yes

Yes Yes Yes

Yes

Legend

W = Cable Tray Width

D = Cable Tray Load Depth

Sd = Sum of Cable Diameters

A = Sum of Cable Areas

S/C = Single Conductor

M/C = Multiconductor Cables

RS = Ladder Rung Spacing

Ampacity: See pages 36 - 38 for information on cable ampacity that

might affect the cable tray sizing flowchart.

See pages 15 - 17 for information on hazardous

(classified) areas that might affect the cable tray sizing

flowchart.

54

Cooper B-Line, Inc Cable Tray Manual

Material NEMA Load Depth*

Aluminum ❏2” ** ❏

Pre-Galvanized Steel ❏3” ❏

Hot-Dip Galvanized Steel ❏4” ❏

304 Stainless Steel ❏5” ❏

316 Stainless Steel ❏6” ❏

Fiberglass-Polyester Resin ❏* Load depth is 1” less than siderail height.

Fiberglass-Vinyl Ester Resin ❏** Fiberglass and wire mesh.

Width Bottom Styles Length Fitting Radius

6” ❏6” ❏Metallic 12” ❏

9” ❏9” ❏120” ❏24” ❏

12” ❏12” ❏144” ❏36” ❏

18” ❏18” ❏240” ❏48” ❏

24” ❏Ventilated Trough ❏288” ❏

30” ❏Solid Trough ❏ Non-Metallic

36” ❏Solid Bottom ❏120” ❏

42” ❏240” ❏

Tray Series NEMA Class

A (50 lbs./ft.) ❏

B (75 lbs./ft.) ❏

B-Line Series OR C (100 lbs./ft.) ❏

Support Span ft.

Load Rating lbs./ft.

Safety Factor

CABLE TRAY INSTALLATION & SPECIFICATION CHECKLIST

Appendix Sheet 9

Project Information

Project Name: #

Location:

Contractor/Engineer:

Phone:

Project Information

Cable Tray

Distributor Name:

Location:

Contact:

Phone: Fax:

55

Cable Tray Manual Cooper B-Line, Inc

CABLE TRAY INSTALLATION & SPECIFICATION CHECKLIST

Appendix Sheet 9

Material Width

Aluminum ❏3” ❏

Pre-Galvanized Steel ❏4” ❏

Hot-Dip Galvanized Steel ❏6” ❏

304 Stainless Steel ❏8” * ❏

316 Stainless Steel ❏* Fiberglass only.

Fiberglass-Polyester Resin ❏

Fiberglass-Vinyl Ester Resin ❏Fitting Radius

Type 0” ❏

Ventilated ❏6” ❏

Non-Ventilated ❏12” ❏

24” ❏

36” ❏

Cable Channel

System Depth*

Data-Track ❏Straight Rung ❏

Verti-Rack ❏2” ❏

Half-Rack ❏3” ❏

Multi-Tier Half Rack ❏4” ❏

6” ❏

Width* Rung Spacing* Tiers* Length

3” ❏6” ❏2❏120” ❏

6” ❏9” ❏3❏144” ❏

9” ❏12” ❏ 4❏

12” ❏18” ❏5❏

18” ❏24” ❏6❏

24” ❏

* Options shown are not available for all systems. Please check B-Line Cent-R-Rail Catalog for availability.

Cent-R-Rail

Width* Depth* Wire Mesh Size Length

2” ❏1” ❏2 x 4 118” (3 meters)

4” ❏2” ❏

6” ❏4” ❏

8” ❏

12” ❏* Widths shown are not available for all depths.

18” ❏Please check B-Line Wire Basket Catalog for availability.

24” ❏

Wire Basket Tray

56

Cooper B-Line, Inc Cable Tray Manual

1 NEMA Standard VE-2, Section 4, Installation 4.3 Straight Section Installation - 4.3.1. Horizontal

Cable Tray Straight Sections states that straight section lengths should be equal to or greater than

the span length to ensure not more than one splice between supports.

Additional Cable Tray Resources

Cable Tray Institute National Electrical Manufacturers Association

1300 N. 17th Street 1300 N. 17th Street

Rosslyn, VA 22209 Rosslyn, VA 22209

www.cabletrays.com www.nema.org

B-Line Engineering Software

TrayCAD®

TrayCAD®is a Cable Tray layout design program that works within the AutoCAD®

environment. TrayCAD®is a windows based program and installs as an add-on to your

AutoCAD®system. Use the TrayCAD®toolbar to add cable tray to your existing plans by

drawing a single centerline representation of the tray run. Then, with the click of a button, the

program will build a full-scale 3-D wire-frame model of the cable tray and all the appropriate

fittings. The program also automatically creates a Bill of Material and contains a library of

modifiable details.

Runway Router®

Runway Router®is a cable ladder runway (ladder rack) layout design program that works within

your AutoCAD®environment. Use the commands from the Runway Router®toolbar to layout

runway, relay racks and electronic cabinets. Add cable tray or Cent-R-Rail®to your existing

plans by drawing a single centerline representation of the cable run. Then, with the click of a

button, the program will build a full-scale 3-D wire-frame model of the cable runway and all the

appropriate connectors and fittings. The program also automatically creates a Bill of Material

and contains a library of modifiable details.

Footnotes:

B-Line Wire Management Resources

B-Line Product Catalogs

• Cable Tray Systems (CT-02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Metallic, Two Siderail System

Commercial and Industrial Applications

• Fiberglass Cable Tray (CT01FRP) . . . . . . . . . . . . . . . . . . . . . . . .

Non-Metallic, Two Siderail Trays

Non-Metallic Strut Systems

• Cent-R-Rail®(CR-02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Center Supported Cable Tray

“Lay-In” Cable Design for Easy Installation

of Low Voltage Cables

• Redi-Rail®(RR-01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pre-Punched Aluminum Side Rail Design

Unmatched Job Site Adaptability for a Two

Side Rail System - Load Depths 2” to 6”

• Wire Basket Runway (WB-02) . . . . . . . . . . . . . . . . . . . . . . . . . . .

Unmatched Adaptability to Site Conditions

Pre-Packaged Installation Kits and Accessories

Fast - Adaptable - Economical

Other B-Line Wire Management Systems

• Telecom (BLT-01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Saunders’ Cable Runway and Relay Racks

Unequal Flange Racks

• Cable Hooks (BLF-02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Supports all Cat 5, Fiber Optic, Innerduct

and Low Voltage Cabling Requirements

• Wireway (ENC-02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Houses Runs of Control and Power Cable

Available in NEMA 12, Type 1 & Type 3R

B-Line Mechanical Support Systems

• Strut Systems (SS-00R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Metal Framing Support System. Fully Adjustable

and Reusable, with a Complete Line of Channel,

Fittings and Accessories for Multi-Purpose Applications

• Seismic Restraints (SRS-02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Multi-Directional Bracing for Electrical Conduit,

Cable Tray and Mechanical Piping Systems.

OSHPD Pre-Approved Details

57

Cable Tray Manual Cooper B-Line, Inc

Cent-R-Rail

Redi-Rail

Wire Basket Metalic

Cable Tray

Non-Metalic

Cable Tray

Ask the Experts

Cooper B-Line, Inc

509 W. Monroe Street

Highland, IL 62249

Phone: 618-654-2184

Fax: 618-654-1917

101102 © 2002 Cooper B-Line