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Cooper Bussmann CT02MAN User's Manual

1. 56 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
2. Test Current Amps And Type Type Fuse Of i i Of Size Connector Connector Adj Vert 1 Bolt Adj Vert 1 Bolt Adj Vert 1 Bolt 288 Adj Vert Adj Vert 2 Bolts 295 igi Rigid 34 000 13 250 Rigid 4 71 Rigid Test current was interrupted in a predetermined time when a fuse was not used lor2 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 Appendix Sheet 1 Cable Tray Manual A5 Cooper B Line Inc Conduit Conduit Cable Tray roy EM d Right Angle Beam Clamp To Current Source UL Listed Conduit Clamp 9ZN 1158 To Current Source Cable Tray Test Set Up Conduit Clamp Detail CIRCUIT ARRANGEMENT FOR RIGID CONDUIT TEMPERATURE RISE TESTS TABLE Ill TEMPERATURE RISE TESTS CONDUIT CLAMPS FOR BONDING RIGID CONDUIT TO CABLE TRAY Rigid Conduit Cable Tray Test Current Amperes Condition After Test Class Material 36 000 Size Material 4 Il Aluminum Aluminum No arcing or damage 20 900 4 Aluminum Aluminum No arcing or damage 12 100 4 Aluminum Aluminum No arcing or damage 21 000 Steel Steel Zinc melted at point where conduit contacted with tray 3 260 21 000 Steel Aluminum Steel Aluminum
3. Use Only As A Mechanical Support For Cables Tubing and Raceways Catalog Number 24A09 12 144 STR SECTION and description Shipping Ticket Mark Number Purchase Order Minimum Area Load Class 260203 00 001 78101115400 D798981 1 000 SQ IN 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 392 8 Cable Installation A Cable S plices 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
4. 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 NECS 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 wir
5. No arcing or damage No arcing or damage 12 100 Aluminum Aluminum No arcing or damage 8 000 Aluminum Aluminum No arcing or damage 21 000 Steel Steel Zinc melted at point where conduit contacted with tray 12 000 Steel Steel Slight arc between clamp and tray 3 240 21 000 Steel Aluminum Steel Aluminum No arcing or damage No arcing or damage 12 200 Aluminum Aluminum No arcing or damage 12 100 Steel Steel No arcing or damage 8 000 Steel Steel No arcing or damage 1 980 200A FU Cooper B Line Inc Steel Steel Appendix Sheet 2 46 No arcing or damage Cable Tray Manual 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 30 Usable Cable Tray Width 29 82 Equals Cable Sd DAQAQAAQAAAAY xxx Cross Section Of The Cables And The Cable Tra 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 l 3 C 500 kcmil 2 26 inches 4 9 04 inches 3 C 250 kcmil 1 76 inches 3 5 28 inches 3 3 C 4 0 AWG 1 55 inches 10 15 5
6. 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 Cable Tray Manual Cable Tray Manual Cooper B Line Inc 43 Appendix Pages Appendix Sheet 1 1 emm nemen nemen nena ns 45 Temperature Rise Tests Cable Tray Connectors Class ll Aluminum amp Steel Ladder Tray Appendix Set SosspppEHEYdNRPNUEEDUR OREFEEREU VOD ENEE DEP DERKEERTM E Di 46 Temperature Rise Tests Conduit Clamps For Bonding Rigid Conduit To Cable Tray Appendix SNET SS 47 Example NEC Section 392 9 A 1 Appendix Sheet 4
7. 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 X1 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 Cable Tray Manual 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 t
8. 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 Ib 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 Ibs 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 c
9. 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 Nomenclature Ladder Type Cable Tray Ventilated Trough Type Cable Tray Splice Plate 90 Horizontal Bend Ladder Type Tray 45 Horizontal Bend Ladder Type Tray Horizontal Tee Ladder Type Tray Horizontal Cross Ladder Type Tray 90 Vertical Outside Bend Ladder Type Tray 45 Vertical Outside Bend Ventilated Type Tray o o O0 Ui i8 UN rz Cable Tray Manual 21 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 1096 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 siz
10. less than siderail height Fiberglass and wire mesh Length Fitting Radius M etallic 12 E 120 q 24 0 144 q 36 A 240 LJ 48 m 288 LJ Non M etallic 120 Q 240 Ly NEMA Class A 50 Ibs ft J B 75 lbs ft n C 100 Ibs ft E Support Span ft Load Rating Ibs ft Safety Factor Appendix Sheet 9 54 Cable Tray Manual CABLE TRAY INSTALLATION amp SPECIFICATION CHECKLIST Cable Channel Aluminum Pre Galvanized Steel Hot Dip Galvanized Steel 304 Stainless Steel 316 Stainless Steel Fiberglass Polyester Resin Fiberglass V inyl Ester Resin Type Ventilated Non Ventilated M aterial n n n n n n n n n Width 3 4 6 a n n n n Fiberglass only Fitting Radius 0 6 12 24 36 n O L L L Cent R Rail System Data Track I Verti Rack I H alf Rack I Multi Tier Half Rack L1 Width Rung Spacing 3 J 6 J 6 J o J 9 12 LU 12 q 18 LI 18 LI 24 LI 24 LI Width 2 4 6 g 12 18 24 Cable Tray Manual D epth Straight Rung 2 3 4 6 Tiers Nu 4 QJ hJ O O C O L LLDLLDLL m Length 120 0 144 d Options shown are not available for all systems Please check B Line Cent R Rail Catalog for availability Wire Basket Tray LLDLDLLDL Depth 1 Uu 2 M 4 LJ Widths shown are not available for all depths Please check B Line Wire Basket Catalog f
11. 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 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
12. 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 Table 4 2 Maximum Spacing Between Expansion J oints That Provide For One Inch 25 4 mm Movement Temp Differential E Aluminum C Feet Stainless Steel 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 Cable Tray Manual 41 Cooper B Line Inc Max Temp Min Temp C9 F F 130 130 50 110 110 40 1 E 36 90 90 FU 490 20 70 70 Pu B c 10 50 gt r gt i 50 t o 30 3 30 og 10 10 10 6 S 20 10 10 30 T 39 2T 30 40 4 Ye 1 4 3e 1 2 5 8 3 4 e Gap Setting in Inches Figure 4 13B Gap Setting Of Expansion Splice Plate 1 25 4 mm Gap Maximum The Gap Setting of the Expansion Joint Splice Plate is used as follows per the example ind
13. Electrical Code and NEC are registered trademarks of the National Fire Protection Association Inc Quincy MA 02269 Cooper B Line Inc Cable Tray Manual WHY CABLE TRAY BECAUSE A CABLE TRAY WIRING SYSTEM PROVIDES SAFE AND DEPENDABLE WAYS TO SAVE NOW AND LATER 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
14. Ladder or Vented Trough Tray No Yes S C 392 10 A 1 1000 W Sd kcmil or larger 392 10 A 2 WzA 1 1 392 10 A 3 S C 250 kcmil d W A 1 1 Sd 392 10 A X4 W gt Sd 9 max RS S C 1 0 thru 4 0 Appendix Sheet 8 52 SUE W gt Sd single layer Start Here 2000V or less cables Yes S C 1 0 No M ulti Yes or larger conductor cables Continued on next No page 392 3 B 1 a Not permitted by the NEC Note Use when mixing 250 thru 1000 kcmil cables with cables larger than 1000 kcmil Cable Tray Manual CABLE TRAY SIZING FLOWCHART 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 Ladder or Vented Trough Tray Solid Channel Tray Vented Channel Tray Solid Bottom Tray Yes 392 9 A W 2 Sd W gt Sd 0 9 single layer 392 9 E 1 M C 4 0 or larger M C 4 0 or larger WxD21 6A single layer No M C smaller than 4 0 M C smaller than 4 0 Yes 392 9 A Q W A 1 2 392 9 C 2 W A 0 9 392 9 E NZ W x D 2 2 9A No 392 9 A X3 392 9 C 3 392 9 F 2 392 9 F 1
15. Manual e he 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 e 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 e More supports are normally required for rigid steel conduit due to the requirements of NEC Table 344 30 B Q e 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 e 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 eq
16. 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 U sed 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 T he 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
17. and or low flame spread ITC or PLTC cables must be used e 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 e 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 Cooper B Line Inc INSTALLATION COST AND TIME SAVINGS e 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 e 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 Cable Tray
18. 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 M CC 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 s
19. 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 Cooper B Line Inc Conduit Bushing Cable Tray Side Rail 16 Feet UL Listed Conduit To Cable Tray Clamp Inch Rigid Metal Conduit P Position Of The First Conduit Support From The Cable Tray Conduit Must Be Cable Tray See NEC Table 344 30 B 2 To Obtain The Support Requirements For Other Conduit Sizes Securely Fastened To The Support Conduit Terminated On And Supported By The Cable Tray Side Rail Installation For Qualifying Industrial Facilities As Per 392 6 UL Listed Conduit To Cable Tray Clamp Conduit Bushing ST Any Size Of Rigid Metal Conduit i U PSP Position Of The First Conduit Support From The Cable Tray Conduit Must Be Securely Fastened To Cable Tray Side Rail 3 Feet or 5 Feet ee eee ions Cable Tray The Support Conduit Terminated On The Cable Tray Side Rail Installation For Commercial And Non Qualifying Industrial Facilities As Per 392 6 392 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
20. 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 2 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 Cooper B Line Inc 34 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 Ventilated Channel M aximum Cross Sectional Cable Tray Size Area of the Cable 3 Inch Wide 4 Inch Wide 6 Inch Wide 2 3 Square Inches 4 5 Square Inches 7 0 Square Inches 392 9 E 2 The fill areas for combinations of multiconductor cables of any type installed in ventilated channel cable tray Vent
21. 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 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 T
22. 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 2 inch 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 e 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 e 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 e 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 Cooper B Line Inc e Moisture is a major cause of electrical
23. 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 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 ca
24. 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 300 amp 600 Cables Rated O ver Volt Cables 600 Volts Are Type MC Cooper B Line Inc No 2 Where separated with a fixed solid barrier of a material compatible with the cable tray 300 amp 600 Fixed Solid Barrier Cables Rated Volt Cables Comparable Material Over 600 Volts N x b NO 2 392 6 Installation G Through Partitions and Walls Whether penetrating fire rated walls with tray cable only or cable tray and t
25. 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 H ere 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 th
26. e Wireway ENC 02 sssesen Houses Runs of Control and Power Cable Available in NEMA 12 Type 1 amp Type 3R B Line Mechanical Support Systems e Strut Systems 23 00 RJ aia ox petet qx iren Feni rdN ES Metal Framing Support System Fully Adjustable and Reusable with a Complete Line of Channel Fittings and Accessories for Multi Purpose Applications e Seismic Restraints SRS 02 0 ee Multi Directional Bracing for Electrical Conduit Cable Tray and Mechanical Piping Systems OSHPD Pre Approved Details Cable Tray Manual 57 Cooper B Line Inc Ask the Experts Cent R Rail _ Redi Rail Non Metalic Cable Tray Wire Basket Cable Tray Cooper B Line Inc 509 W Monroe Street Highland IL 62249 Phone 618 654 2184 Fax 618 654 1917 101102 2002 Cooper B Line
27. 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 e n 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 Cooper B Line Inc 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 6
28. 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 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 Ibs ft B for 75 Ibs ft and C for 100 Ibsj 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 Ibs linear foot The cable load per foot is easy to calculate us
29. metal covers This is Cooper B Line Inc 18 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 Ibs 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
30. 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 Cooper B Line Inc QRSSIE 30 Do Not Use As A Walkway Ladder Or Support For Personnel VENTILATED 09 05 2002 B Line 816 LIONS DRIVE TROY IL 62294 618 667 6779 1 of 1 30781011154005 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 cable
31. 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 Cooper B Line Inc 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 Cabl
32. s sss mmm nenne nen ns 48 Example NEC Section 392 9 A 2 APPRODO SIGCSE B orunmieden oL A EDI ORUM ETBIOCLU II EIER VINE ER PODER E 49 Example NEC9 Section 392 9 A 3 Appendix Sheet 6 ssosssesssen mmm enne nina nana na nnns 50 Example NEC9 Section 392 9 B Appendix Sheet Z iussererodx vruaulalitua ert etin cdd asa Ada eis aln a Fac M RR Udo Va do CE iu vw baa 51 Table 250 122 Minimum Size EGC for Raceway and Equipment Appendix Sheet 8 iit eect cere tt tt vis Po ERU ret ee re ee du AS DR rer Te 52 53 Cable Tray Sizing Flowchart APPEND SDEEL eet ot here er ee ee te eee 54 55 Cable Tray Installation amp Specification Checklist Appendix Sheet 10 56 Additional Cable Tray Resources and Engineering Software Appendix Sheet Ll oen eps EU EFEREFUHIERPPDRDOPEBISTMDEPUHIEL TERI FEREI XrPEVIM PENATI DePKE OPEN 57 B Line Wire Management Resources Cooper B Line Inc da Cable Tray Manual TABLE TEMPERATURE RISE TESTS CABLE TRAY CONNECTORS CLASS Il ALUMINUM LADDER CABLE TRAY Test Connector Data Amps And Type Type Fuse Of i i Of Size Connector Connector Adj Vert 1 Bolt Rigid Corroded 12 000 Rigid Corroded Bond 12 000 Rigid Rigid Corroded Corroded 34 600 Rigid 3 0 CU Corroded Bond 34 400 Rigid Rigid Corroded Corroded TABLE Il TEMPERATURE RISE TESTS CABLE TRAY CONNECTORS CLASS II STEEL LADDER CABLE TRAY
33. 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 Cooper B Line Inc 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 Solid Unventilated Cable Tray Cover Applicable Ampacity Tables Special Conditions 1 0 AWG and Larger 1 0 AWG and Larger 1 0 AWG amp Larger In Single Layer No Cover Allowed c Yes Maintained Spacing Of One Cable Diameter No Cover Allowed Ca Single Conductors In Triangle Config 1 0 AWG and Larger Spacing
34. 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 Cable Tray Manual 25 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 O ver 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 of the 2002 NEC was changed Instead of allowing only
35. 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 co
36. 0 inches The sum of the diameters Sd of all cables Add Sds for items 1 2 amp 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 1096 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 Ibs ft without equipment grounding conductors 69 9 Ibs ft with equipment grounding conductors This load can be supported by a load symbol B cable tray 75 Ibs ft Appendix Sheet 3 47 Cable Tray Manual Cooper B Line Inc 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 30 Usable Cable Tray Width Cross Section Of The Cables And The Cable Tra 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 l 3 C 12 AWG 0 17
37. 40 645 725 760 770 800 820 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 9 Article for specifics H aving 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 Cable Tray Manual 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 o
38. CTO2MAN Based on the 2002 National Electrical Code EE COOPER B Line Table of Contents Page No Jugis m c E 2 Why Cable Tray wj 3 Bier TR TET TU T UUTMTTTTMTMMTmMMS 4 DCS WINGS ea cenienr enon a ode nee 5 8 An In depth Look at the 2002 NEC Section 392 Types of Cable Trays NEC 392 1 5 CODB bususeuturcumavupxTSaS Eme iMd DETUR DURER PUE XE BRE 9 11 EMI RELCSDI lay Soror ivdusi E FRXEEEVEFDEVEREURNTUR E PIERII EE MS 10 11 DIS Tra Mater Tels a PEE E ELE EREREPEDLET DIE EE 12 Types of Cables Allowed in Cable Tray 392 3 A J snnmm HH 12 MI Mineral Insulated M etal Sheathed Cable Article 332 12 MC Metal Clad Cable Article 330 eeennnnmmmHHH mnn 13 TC Power and Control Tray Cable Article 336 eene 13 ITC Instrumentation Tray Cable Article 727 eeenm e 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 amp Type MV Cables 392 3 BJ emme HH 14 Cable Tray Use in Hazardous Locations 392 3 DJ ennm 15 17 Limitations on Cable Tray Use 392 4 uaccuntimimidesetsbimescbriu sud spd U
39. 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 BX1 2 3 amp 4 600 kcmil and Larger Solid U nventilated Cable Tray Cover No Cover Allowed 9 Applicable Ampacity Tables 310 17 and 310 19 Special Conditions 600 kcmil and Larger Yes 310 17 and 310 19 1 0 AWG through 500 kcmil No Cover Allowed di 310 17 and 310 19 1 0 AWG through 500 kcmil Y es 310 17 and 310 19 1 0 AWG amp Larger In Single Layer No Cover Allowed e 310 17 and 310 19 Maintained Spacing Of One Cable Diameter Single Conductors In Triangle Config 1 0 AWG and Larger No Cover Allowed c 310 20 See NEC Section 310 15 B Spacing Of 2 15 x One Conductor O D Between 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 interp
40. 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 Il 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 Il 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 Il 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 1 be installed in solid bottom cable trays Required Spacing
41. 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 BJ 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 Larg
42. OFING 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 Cooper B Line Inc 40 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 mus
43. Of 2 15 x One Conductor O D Between Cables No Cover Allowed E 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 Cooper B Line Inc 38 DQA Spacing Between Conductors 2 15 x O D of Conductor Technically Undesirable Installation Interpretation 1 Spacing Between Conductors 2 15 x O D of Conductor Technically Desirable Installation Interpretation 2 CABLE TRAY WIRING SYSTEM DESIGN AND INSTALLATION HINTS Cable tray wir
44. PC AF NEPURUPCspPD PH enn IR 18 Cable Thay eroe 59215 A e 18 20 Fiberglass Gable Tray 392 3 45 6 392 5 TES acess ct sentria exten Eo ROUES KP pURSe duin en 20 Discontinuous Cable Tray and Fittings 392 6 A xsskisenstrr acie veu dvbePeEe PRA YR XA EDS 21 22 Go sU T e m 23 sica ici NR Mid T 24 Spacing of Multiple Cable Trays 392 6 l senmm ml 25 Supporting Conduit from Cable Tray 392 6 J smi 25 Use of Cable Tray as an Equipment Grounding Conductor 392 7 Grounding 26 29 Fastening Cables 392 8 4B m 30 Cable I stallaton 392 0 kee en eer er ee ee et ee 30 32 Sizing Cable Tray Multiconductor 2000 volts or less 392 9 eee 32 34 Single conductor 2000 volts or less 392 10 eee 34 36 Type MC or MV 2001 volts or greater 392 12 enne 37 Ampacities of Cables In Cable Tray assessimsesus Inte suzeuz rest ac Dna E EU RE URN EE Y EV Ex er E ecu 36 38 Cable Tray Wiring System Design and Installation Hints cccsceceeeecseeeeeeeteeeeees 38 39 gltseioronuoW sci T e 40 bier inco gis pe CONAC NO nm 41 42 Appendix Index amp Appendix Sheets sssssseemH 44 55 Cable Tray Installation amp Specification Checklists 54 55 axluupr c A
45. W z A 1 2 4 Sd we AtSd W xD 3 2A WxDz1 9A 0 9 Note The value A only applies to cables smaller than 4 0 No The value Sd only 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 applies to 4 0 and larger cables which W Cable Tray Width must be single layer D Cable Tray Load Depth Sd Sum of Cable Diameters M C Y es B M C A Sum of Cable Areas oe m contro S C Single Conductor and or W xD 22A and or signal signal M C Multiconductor Cables RS Ladder Rung Spacing Appendix Sheet 8 Cable Tray Manual 53 Cooper B Line Inc CABLE TRAY INSTALLATION amp SPECIFICATION CHECKLIST Project Information Project Name Location Contractor Engineer Phone Project Information Distributor Name Location Contact Phone Fax Cable Tray M aterial Aluminum Pre Galvanized Steel Hot Dip Galvanized Steel 304 Stainless Steel 316 Stainless Steel Fiberglass Polyester Resin Fiberglass V inyl Ester Resin Width 6 9 12 18 24 30 30 42 O L L L L L L L B Line Series Cooper B Line Inc LLDLDLDLLDL Bottom Styles e 9 12 18 Ventilated Trough Solid Trough Solid Bottom O L L L L L L Tray Series NEMA Load Depth 2 x L 3 E 4 E 5 E 6 E Load depth is 1
46. art 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 Cable Tray Manual 15 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 Establishm
47. at 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 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
48. 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 Cooper B Line Inc 26 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 Cable Tray Manual Discontinuous J oints Require Bonding For Qualifying Facilities EGCs in the Cables or EGC Cables Are Not Required If Rating Of The Feeder O vercurrent D evice Permits Using The Tray For the EGC Transformer Solidly Grounded Secondary Bonding J umper Not Required For Rigidly Bolted J oints Conduit Three Phase Motor Installation v b Motor Control Center Building Steel Ground Bus Bonded To Enclosure Lightning A Protection Grounding X Es System Ground 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 9 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 magnet
49. ble tray See also Section 250 120 for additional information Cooper B Line Inc 28 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 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 temp
50. ble 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 H owever at this time no fill rules for single conductor cables in solid bottom cable tray have been established see Section 392 3 B 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 P
51. 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 Cable Tray Manual high winds the light duty clips are not capable of restraining the covers Outdoor cover installations should be overlapped at expansion joint locations to
52. 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 Cooper B Line Inc 14 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
53. cables to be installed in Class Division 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 Cooper B Line Inc 501 4 A 1 d allows Type ITC HL cable to be installed in Class Division 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 bee
54. e 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 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 e Most projects are roughly defined a
55. e 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 NECS 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 e
56. e cable requirements for zone locations 392 3 Uses Permitted Cable Tray E Nonmetallic 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 H ere the amperages are very high and significant stray current paths are present Under such conditions there is the possibility for a 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
57. e 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 U nited 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 5096 Also aluminum cab
58. e 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 Cable Tray Manual 392 11 Ampacity of Cables Rated 2000 Volts or Less in
59. e usually encloses the cable s conductors These cables are used to transmit the low energy level signals associated with the industrial 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
60. ed 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 Typical Cable Tray Layout 30 Vertical Inside Bend Ladder Type Tray Vertical Bend Segment VBS Vertical Tee Down Ventilated Trough Type Tray Left Hand Reducer Ladder Type Tray Frame Type Box Connector Barrier Strip Straight Section Solid Flanged Tray Cover Cable Channel Straight Section Ventilated Cable Channel 90 Vertical Outside Bend Cooper B Line Inc 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 NEC9 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 co
61. 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 Solid Non Flanged Solid Flanged Raised Cover Clamp Combination Cover amp Hold Down Clamp d Standard Cover Clamp H eavy Duty Cover Clamp Cover J oint Strip Aluminum Cable Tray Cover Accessories Equivalent Items are available for Steel Cable Trays Cooper B Line Inc 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
62. ent 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 Division 1 Gases or Vapors 501 A A 1 b Type MI cable may be installed in cable tray in this type of hazardous classified area 501 4 A K1 c allows Type MC HL
63. 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 e n 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
64. er 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 Cooper B Line Inc 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
65. erature 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 Cable Tray Manual Temperature Rise Test Material Thickness 0 125 Aluminum or 14 Gauge Steel V 4 M 91 2 Adjustable V ertical Cable Tray Connectors Cross Section Area 2 Rails 13 I 16 i Aluminum 1 00 sq in Steel 0 76 sq in 3 I 41 2 n 0 080 Aluminum or 14 Gauge Steel Gd 3 8 Bolting Hardware Cross Section Cable Tray Side Rail Insulated J oints TON Fuse if used Current Source T Cable Lug C1 500 kcmil copper Type RH Insulation LIE d I LI ld T T Cable Lug C2 C3 T Temperature M easurement at each Tray Connection C1 C2 amp C3 Cable Tray Connectors or Bonding J umpers Figure 1 See Page 45 Appendix Sheet 1 392 7 Grounding B Steel or Alumi
66. ery 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 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 Cooper B Line Inc 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 mor
67. f the NEC contact National Fire Protection Association 1 Batterymarch Park P O Box 9101 Quincy Massachusetts 02269 9101 1 800 344 3555 392 1 Scope Standard Aluminum Ladder 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 e he 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 e 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 e Moisture cannot accumulate in ladder cable trays and be piped into electrical equipment as happens in conduit systems e Ladder cable tray cannot pipe hazardous or explosive gasses from one area to another as happens with conduit systems n 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 Cable Tray Manual overall strength of the cable tray Specifiers should be
68. ficiently strong splice plates Cable Tray Manual 11 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 Ibs 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 Ibs ft on a 20 foot span A NEMA 20A tray 50 Ibs ft on a 20 foot span will support over 130 Ibs 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
69. ghting 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 Il Division 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 Cable Tray Manual 17 in ordinary locations 503 3 Wiring Methods A Class Ill Division 1 and B Class Ill 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
70. ic 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 Cable Tray Manual See Table 250 122 on page 51 for the minimum size EGC for grounding raceway and equipment 27 Cooper B Line Inc 392 7 Grounding B Steel or Aluminum Cable Tray Systems 1 amp 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
71. icated 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 Cooper B Line Inc this intersection point project down to the gap setting horizontal axis to find the correct gap setting value Example s Value 3 8 inch 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 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 As a clamp As a guide
72. ilated Channel Maximum Allowable Cable Tray Size Fill Area 3 Inch Wide 4 Inch Wide 6 Inch Wide 1 3 Square Inches 2 5 Square Inches 3 8 Square Inches 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 Solid Channel Maximum Cross Sectional Cable Tray Size Area of the Cable 2 Inch Wide 3 Inch Wide 4 Inch Wide 6 Inch Wide 1 3 Square Inches 2 0 Square Inches 3 7 Square Inches 5 5 Square Inches Cable Tray Manual 392 9 F 2 The fill areas for combinations of multiconductor cables of any type installed in solid channel cable tray Solid Channel Maximum Allowable Cable Tray Size Fill Area 2 Inch Wide 3 Inch Wide 4 Inch Wide 6 Inch Wide 0 8 Square Inches 1 1 Square Inches 2 1 Square Inches 3 2 Square Inches 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 Ladde
73. in Cable Trays for Type MC MI amp TC Cables in Class Il Division 2 Hazardous Classified Areas Cable Tray Manual 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 li
74. ing 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 Ibs 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 Ibs ft Total 26 20 Ibs ft 3 3 C No 250 kcmil 3 18 Ibs ft Total 9 54 Ibs ft 4 3 C No 500 kcmil 5 87 Ibs ft Total 23 48 Ibs ft Total Weight of the Cables 2 59 22 Ibs 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 Ibs ft If this cable tray is Cable Tray Manual 19 installed indoors a load symbol B cable tray would be adequate
75. ing 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 Cable Tray Manual e 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 pro
76. insulated multiconductor instrumentation tray cables ITC and power limited tray cables PLT C cost the same for both cable tray and conduit wiring systems This applies for instrumentation circuits low level analog and digital Cooper B Line Inc COST Cable Tray vs Conduit Equivalent Conductor Fill Areas 16000 Material Cost 14000 Labor Cost 9 25 hr per NECA 12000 labor units 10000 T otal Installed 8000 Cost 6000 4000 2000 0 Ladder Solid Bottom EMT Rigid Steel Cable Tray Cable Tray Conduit 1 2 3 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 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
77. inuous 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 Cooper B Line Inc 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 e 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 e Airport facilities have extensive cable tray wiring systems to handle the ever expanding needs of the airline industry
78. ion 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 Aluminum Solid Bottom Trough 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 4 inch weep holes be drilled in their bottoms at the sides and in the middle every 3 feet to limit water accumulation Cable Tray Manual 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 Center Supported Cable Tray B Line s Cent R Rail Sys
79. 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 O ptical fiber cables have been allowed to be supported in cable trays as per Section 770 6 O ptical 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 NECS 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 NECS solid bottom ca
80. ld be much greater e 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 e 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 e Excluding conductors the cost of the cable trays supports and miscellaneous materials will provide a savings of up to 8096 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 e 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 e 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
81. le 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 NECS 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 NECS cable tray installations that supplied support for conduits were not restricted to qualifying industrial facilities The 1996 NECS Section 392 6 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
82. le 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 Cooper B Line Inc 20 392 5 Construction Specifications B S mooth 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
83. n 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 Cooper B Line Inc 16 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
84. nductor 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 PT 24 Usable Cable Tray Width EE Cross Section Of The Cables And The Cable Tra 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 l 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 amp 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 2 3 C 2 AWG 0 80 sq in 4 3 20 sq in Total cable tray width required for items 3 4 amp 5 6 in 6 in 10 6 sq in 7 sq in at 7 sq in Actual cable tray width is A Width 12 98 in B Width 9 09 in 2 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 3 40 s
85. nductors 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 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 Cable Tray Manual Cooper B Line Inc 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 installa
86. nduit 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 Cooper B Line Inc 22 T NEUFS 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 Cables Entering and Exiting Motor Control Centers from Cable Tray Systems 392 6 Installation B Completed Before Installation This means th
87. num Cable Tray Systems 3 amp 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 amp 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 Cable Tray Manual 29 99 N1 600 amps max 2000 amps max 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 Cooper B Line Inc Cable Tray Label WARNING
88. o 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 Cable Tray Manual 33 392 9
89. ome 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 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 J ust as for ladder cable tray ventilated trough cable tray will not pipe moisture into electrical equipment Standard widths for ventilated trough cable tray
90. oncentrated 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 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 th
91. or availability Appendix Sheet 9 55 Wire Mesh Size Length 2x4 118 3 meters Cooper B Line Inc Footnotes 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 A utoCA D 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 9 environment Use the commands from the Runway Router toolbar to layout runway relay racks and electronic cabinets Add cable tray or Cen
92. ped 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 e n 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 e n facilities where cable tray may be used as the equipment grounding conductor in accordance with NEC Sections 392 3 C amp 392 7 the grounding equipment system components lend them
93. per cable tray in the correct location routing cables through the tray system and controlling the cable fill area requirements e 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 e The Cable Number the Cable Manufacturer amp Catalog Number Number of conductors the conductor sizes and the approximate cable length e 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 e 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 e 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 contin
94. per B Line Inc 50 Cable Tray Manual Cable Tray Manual 400 500 600 800 1000 1200 1600 2000 2500 3000 4000 5000 6000 Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of Equipment Conduit etc Not Exceeding Amperes Copper Appendix Sheet 7 51 Size Table 250 122 Minimum Size Equipment Grounding Conductors for Grounding Raceways and Equipment AWG or kcmil 3 0 4 0 250 350 400 500 700 800 Aluminum or Copper Clad Aluminum m e O N FAN BO CO CO CO 0 2 0 3 0 4 0 250 350 400 600 600 800 1200 1200 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 Cooper B Line Inc CABLE TRAY SIZING FLOWCHART Sizing Cable Tray Per NEC 392 Vented Channel Tray 392 10 No 392 10 B recognized by W 2 Sd the NEC Note The value A only applies to cables 250 up to 1000kcmil The value sd only applies to 1000 kcmil and larger cables 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 Cooper B Line Inc
95. q in 4 00 sq in 3 20 sq in 1 9 09 inches 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 Cables copper conductors with cross linked polyethylene insulation and a PVC jacket Total cable weight per foot for this installation 40 2 Ibs ft Cables in this example do not contain equipment grounding conductors This load can be supported by a load symbol A cable tray 50 Ibs ft Appendix Sheet 5 Cable Tray Manual 49 Cooper B Line Inc Example NEC Section 392 9 B Cable Tray containing Type ITC or Type PLTC Cables 6 Usable Cable Tray Width 4 Usable Cable Tray Depth Cross Section Of The Cables And The Cable Tray 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 12 sq in 300 cables can be installed in this cable tray 0 04 sq in cable 300 cables 11 54 rows can be installed in this cable tray 26 cables rows 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 Appendix Sheet 6 Coo
96. r 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 Cable Tray Manual Cable Tray Width Single Conductor Size 1 0 2 0 3 0 4 0 250 Kcmil 350 Kcmil 500 Kcmil 750 Kcmil Notes 1 Cable diameter s used are those for Okonite Okolon 600 volt single conductor power cables 2 3 42 inch wide is ladder cable tray only Such installations are to be made only in qualifying industrial facilities as per Sections 392 3 B amp B1 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 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 ve
97. ray 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 See po 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 Cable Tray Manual 24 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 Cab
98. rees 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 amp 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 Cooper B Line Inc 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 Splice Vertical Adjustable Splice Cable Support Fitting FIREPRO
99. 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 e Safety Features e Dependability e Space Savings e Cost Savings Design Cost Savings Material Cost Savings e Installation Cost amp Time Savings Maintenance Savings Cable Tray Manual 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 pi
100. retations 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 Cable Tray Manual Spacing Between Conductors 2 15 x O D of Conductor Technically U ndesirable Installation Interpretation 1 Spacing Between Conductors 2 15 x O D of Conductor Technically Desirable Installation Interpretation 2 392 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
101. ry 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 Cooper B Line Inc 35 392 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 3 Inch V Channel 6 Inch V Channel 4 Inch V Channel Diameter Inches Single Conductor Size Note 1 EST E ET 1 0 AWG 2 0 AWG 3 0 AWG o m 4 0 AWG 250 Kcmil 350 Kcmil 500 Kcmil 750 Kcmil 1000 Kcmil NININIWwWI W 4 I Ul NN Ww wy Be By Oo uU oc AIAIAIO OJ N CO C WO Notes 1 Cable diameter s used are those for Okonite Okolon 600 volt single conductor power cables 32 Such installations are to be made only in qualifying industrial facilities as per Sections 392 3 B amp B1 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 ev
102. s were not tied down properly Cable Tray Manual 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 Channel to Tray Channel to Channel Cable Channel Branch Circuit 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
103. selves to visual inspection as well as electrical continuity checks 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 e 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 e 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 cont
104. sq in 20 3 40 sq in 2 4 C 12 AWG 0 19 sq in 16 3 04 sq in B 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 amp 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 amp 4 multiplied by m cable tray width required 3 40 sq in 3 04 sq in 6 02 sq in 16 00 sq in 28 46 sq in 28 46 sq in x 6 in 7 sq in 24 39 inch cable tray width required 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 Ibs ft Cables in this example do not contain equipment grounding conductors This load can be supported by a load symbol A cable tray 50 Ibs ft Appendix Sheet 4 Cooper B Line Inc AR Cable Tray Manual Example NEC Section 392 9 A 3 Width selection for cable tray containing 600 volt multico
105. 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 4 inch 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 Vent Channel Cable Tray B Line s Cable Channel Cooper B Line Inc 10 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 ventilat
106. t 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 Cooper B Line Inc 56 Cable Tray Manual B Line Wire Management Resources B Line Product Catalogs e Cable Tray Systems CT 02 sss Metallic Two Siderail System Commercial and Industrial Applications Fiberglass Cable Tray CTOIFRP 0 Non M etallic Two Siderail Trays Non M etallic Strut Systems e Cent R Rail CR 02 0 0 ee Center Supported Cable Tray Lay In Cable Design for Easy Installation of Low Voltage Cables e Redi Rail8 RR 01 ssssssseRRRRRRR Pre Punched Aluminum Side Rail Design U nmatched J ob Site Adaptability for a Two Side Rail System Load Depths 2 to 6 e Wire Basket Runway WB 02 eese U nmatched A daptability to Site Conditions Pre Packaged Installation Kits and Accessories Fast Adaptable Economical Other B Line Wire Management Systems e Telecom BLT 01 ssssse Saunders Cable Runway and Relay Racks U nequal Flange Racks e Cable Hooks BLF 02 oss math dau den wi FORE REP rdg Supports all Cat 5 Fiber Optic Innerduct and Low Voltage Cabling Requirements
107. t 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 Cable Tray Manual 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
108. t 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 e 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 e 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 Cable Tray Manual monitored For an equal capacity wiring system only a few cable tray runs would have to be monitored e 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 wou
109. tem 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 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 4 span is not critical in a short or intermediate span application given that most trays have suf
110. tice 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 O verfill of the cable tray with the conductors Cooper B Line Inc 32 Compatibility Of Cable Tray Types And Cable Trays Based On The NEC9 3 4 amp 6 Wide Solid or Ventilated Channel Cable Tray Solid Bottom Cable Tray Ventilated Trough Cable Tray Ladder Cable Tray mmm M ulticonductor Cables 300 amp 600 Volt Single Conductor Cables 600 Volt Type MV Multiconductor Cables Type MV Single Conductor Cables 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 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
111. tions 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 Conductors E Single 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 prac
112. uipment 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 Cable Tray Manual 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 e Conductor insulation damage is common in conduits since jamming can occur when pulling the conductors J amming 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
113. um 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 Cable Tray Manual 13 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
114. uously upgraded If a specified cable tray run or section becomes overfilled it will be flagged for corrective action by the designer e 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 Cable Tray Manual 39 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 deg
115. xplicitly permit their use in cable trays These circuit types include services feeders branch circuits communication circuits control circuits and signaling circuits Cooper B Line Inc 12 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 Methods This section identifies the 300 amp 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 NECS 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 A Wiring For
116. ype 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 and Class Il Division 1 areas For Type MC cables to qualify for installation in Class and Class II Division areas Section 501 4 A 1 c amp d they must have a gas vapor tight continuous corrugated alumin

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