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What is Cable Tray?

  1. What is a Cable Tray System?
  2. What standards / guidelines are available for cable tray systems?
  3. What types of Cable Tray are available?
  4. How do I know what type of cable tray is right for my application?
  5. What materials / finishes are available for the various cable tray systems?
  6. Now that I know what types of cable trays are available, what configurations are available?
  7. After selecting the type of cable tray and configuration required, what support methods are available?
  8. Before selecting the type of cable tray, cable tray configuration(s), and support method desired, what additional information do I need to supply to the cable tray manufacturer for them to best understand and satisfy my needs?

to top of pageWhat is a Cable Tray System?

Per the National Electrical Code, a cable tray system is "a unit or assembly of units or sections and associated fittings forming a rigid structural system used to securely fasten or support cables and raceways."

What does this mean? to top of pageWhat standards / guidelines are available for cable tray systems?
  1. The National Electrical Code publishes the standards for all types of electrical applications. Articles 318, 250, and 800 cover various aspects of cable tray systems.
  2. NEMA, (National Electrical Manufacturers Association), is an association comprised of the major cable tray manufacturers in the industry. This committee has published three documents to date: NEMA VE1, FG1 and VE2. 

    NEMA VE1 covers general cable tray definitions, manufacturing standards, performance standards, test standards, and application information.  Free download of this document is available on the NEMA website.

    NEMA FG1 addresses the standards for fiberglass cable tray systems. Free download of this document is available on the NEMA website.

    NEMA VE2 is a cable tray installation guideline which covers receiving and unloading material, storage of material, and general installation practices. Free download of this document is available on the NEMA website.

  3. CTI, (Cable Tray Institute), is a trade association comprised of the major cable tray manufacturers in the industry and was formed to provide specifiers, designers, and installers information on the advantages of using cable tray systems over other types of products. (i.e. conduit, ladder rack, etc.)
to top of pageWhat types of Cable Tray are available?
  1. Ladder
  2. Solid Bottom
  3. Trough
  4. Channel
  5. Wire Mesh
  6. Single Rail
to top of pageHow do I know what type of cable tray is right for my application?
  1. Ladder Cable Tray provides:
    1. Solid side rail protection and system strength with smooth radius fittings and a wide selection of materials and finishes.
    2. maximum strength for long span applications
      standard widths of 6,12,18, 24, 30, and 36 inches
    3. standard depths of 3, 4, 5, and 6 inches
    4. standard lengths of 10, 12, 20 and 24 feet
    5. rung spacing of 6, 9, 12, and 18 inches
    Ladder cable tray is generally used in applications with intermediate to long support spans, 12 feet to 30 feet.
     
  2. Solid Bottom Cable Tray provides:
    1. Nonventilated continuous support for delicate cables with added cable protection available in metallic and fiberglass.
    2. Solid bottom metallic with solid metal covers for nonplenum rated cable in environmental air areas
    3. standard widths of 6, 12, 18, 24, 30, and 36 inches
    4. standard depths of 3, 4, 5, and 6 inches
    5. standard lengths of 10, 12, 20 and 24 feet
    Solid Bottom cable tray is generally used for minimal heat generating electrical or telecommunication applications with short to intermediate support spans of 5 feet to 12 feet.
     
  3. Trough Cable Tray provides:
    1. Moderate ventilation with added cable support frequency and with the bottom configuration providing cable support every 4 inches. Available in metal and nonmetallic materials.
    2. standard widths of 6, 12, 18, 24, 30, 36 inches
    3. standard depths of 3, 4, 5, and 6 inches
    4. standard lengths of 10, 12, 20 and 24 feet
    5. fixed rung spacing of 4 inch on center
    Trough cable tray is generally used for moderate heat generating applications with short to intermediate support spans of 5 feet to 12 feet.
     
  4. Channel Cable Tray provides:
    1. an economical support for cable drops and branch cable runs from the backbone cable tray system.
    2. standard widths of 3, 4, and 6 inches in metal systems and up to 8 inches in nonmetallic systems.
    3. standard depths of 1¼-1¾ inches in metal systems and 1, 1 1/8, 1 5/" and 2 3/16 inches in nonmetallic systems
    4. standard length of 10, 12, 20 and 24 feet
    Channel cable tray is used for installations with limited numbers of tray cable when conduit is undesirable. Support frequency with short to medium support spans of 5 to 10 feet.
     
  5. Wire Mesh Cable Tray provides:
    1. A job site, field adaptable support system primarily for low voltage, telecommunication and fiber optic cables. These systems are typically steel wire mesh, zinc plated.
    2. standard widths of 2, 4, 6, 8, 12, 16, 18, 20, and 24 inches
    3. standard depths of 1, 2, and 4 inches
    4. standard length of about 10 feet (118")
    Wire Mesh tray is generally used for telecommunication and fiber optic applications and are installed on short support spans, 4 to 8 feet.
     
  6. Single Rail Cable Tray provides:
    1. These aluminum systems are the fastest systems to install and provide the maximum freedom fort cable to enter and exit the system.
    2. Single hung or wall mounted systems in single or multiple tiers.
    3. Standard widths are 6, 9, 12, 18, and 24 inches.
    4. Standard depths are 3, 4, and 6 inches.
    5. Standard lengths are 10 and 12 feet.
    Single Rail Cable Tray is generally used for low voltage and power cables installations where maximum cable freedom, side fill, and speed to install are factors.
to top of pageWhat materials / finishes are available for the various cable tray systems?
  1. Steel (Min. Yield = 33KSI) (35 KSI for Stainless)
    1. Plain: hot rolled pickled and oiled steel per ASTM A569 (Commercial Quality) or A570 (Structural Quality)
    2. Pre-Galvanized: mill galvanized steel per ASTM A653 CS (Commercial) or SS (Structural) G90
    3. Hot Dip Galvanized After Fabrication: plain steel which is hot dipped after fabrication per ASTM A123.
    4. Stainless Steel: type 304 or 316L fully annealed stainless steel
     
  2. Aluminum (Min.Yield = 23 KSI)
    1. 6063-T6 or 5052-H32 alloy per ASTM B209
     
  3. Fiber Reinforced Plastic (FRP)
    1. Polyester and Vinyl Ester resin systems available
    2. meet ASTM E-84 smoke density rating; Polyester 680, Vinyl Ester 1025
    3. Class 1 Flame Rating and self-extinguishing requirements of ASTM D-635.
to top of pageNow that I know what types of cable trays are available, what configurations are available?
  1. Straight sections are available to route cables in a horizontal or vertical plane.
  2. Fittings are available to route cables in various directions in either the horizontal or vertical planes. Typical examples of fittings include elbows, tees, crosses, and risers. Each of these fittings are available in various radii and bend angles.
  3. Covers are accessories and shouldn't be in here unless splices etc. are included.
to top of pageAfter selecting the type of cable tray and configuration required, what support methods are available?
  1. Trapeze Support (Single or Multi-tier)
  2. Hanger rod clamps, "J" hangers
  3. Center Hung Support
  4. Wall Support
  5. Underfloor Support
  6. Pipe stanchions or other structures

Each of these support methods are preferable in different applications. For instance, trapeze supports may be desired in an application where cables will be pulled through the cable tray. Center hung supports, on the other hand, are generally used when cables will be installed from the side of the cable tray. Center hung supports are especially useful when future cable additions are desired. Wall supports and underfloor supports are useful when ceiling structure is not available or undesired. Outdoor installations are controlled by the structures available to support the cable tray.

to top of pageBefore selecting the type of cable tray, cable tray configuration(s), and support method desired, what additional information do I need to supply to the cable tray manufacturer for them to best understand and satisfy my needs?
  1. Where? Job site and installation considerations
    1. Outdoor
      1. supports available affect the length and strength requirements
      2. environmental loads, ice, wind, snow, and possibly seismic
      3. corrosion requirements affect the materials and finishes
      4. classified hazardous locations affect the cable types acceptable
    2. Indoor
      1. support locations available affect the length and strength of the system
      2. industrial installation may require a 200 lb. Concentrated Load
      3. commercial or institutional installation may make system appearance, system weight, and space available important factors
      4. environmental air handling area may affect cable types, cable tray material, or cable tray type and need for covers
      5. classified hazardous locations affect the cable types acceptable

  2. What?
    1. Type and number of cables to support
      1. NEC cable fill requirements dictate size, width and depth, of system
      2. cable support requirement may control bottom type
      3. largest bending radius of cable controls fitting radius
      4. total of cable weight determines load to support
    2. Future requirements
      1. cable entry / exit freedom
      2. design partially full or an expandable system
      3. support type to allow for needs
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