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TABLE 1 – NEMA CLASSES AND LOAD RATINGS

                           NEMA Standard VE-1   8A-12A  12B     12C      16A     A6B     16C     20A      20B     20C
                           Load/Span Class

                                              50 lb./ft   70 lb./ft   100 lb./ft   50 lb./ft   75 lb./ft   100 lb./ft   50 lb./ft   75 lb./ft   100 lb./ft
                           NEMA Load/Span
                                              12' span  12' span  12' span  16' span  16' span  16' span  20' span  20' span  20' span


                                               Selecting the Tray – Key Considerations
                                               The first step is to determine what type of system is best for the intended application.
                                               Weight capacity and cable volume must be calculated to specify the correct tray criteria,
                                               and trays requiring greater span distances will require a greater cross-sectional area
                                               for the side rails. This is classified and defined in the VE-1 standards. See Table 1 for an
                                               overview of NEMA classes and load ratings.

                                               Knowing the type of cable and the environment in which it will be installed will determine
                                               the type of cable tray you need.

                                                  LADDER TRAY
                                                  A ladder tray is a prefabricated metal structure consisting of two side rails
                                                  connected by individual transverse members or rungs. Used in most cable tray
                                                  system installations, ladder trays provide maximum ventilation for cabling. Ladder
                                                  trays are commonly used in exposed areas like industrial facilities or data centers.


                                                  VENTILATED TROF
                                                  A prefabricated metal structure with clear openings up to 4". Trof cable trays are
                                                  the best choice for smaller cables. Ventilated trofs offer enhanced airflow while
                                                  eliminating cable sagging. The vent holes may be bushed with a grommet for
                                                  dropping out communication cables.

                                                  SOLID TROF
                                                  The bottoms of solid trofs have no openings within the cable bearing surface. Solid
                                                  bottom cable trays eliminate cable sagging and offer the most protection for cables.
                                                  A trof is usually optimal for any size cable. The bottom design also offers safety and
                                                  security from unauthorized personnel.

                                                  CHANNEL
                                                  A channel tray consists of a one-piece ventilated or solid bottom channel section up
                                                  to 6” wide. Offered in ventilated or solid bottom, channel systems with pre-punched
                                                  holes allow the secure attachment of cables to the inside of the channel without
                                                  the need to drill holes, reducing labor and speeding up installation. Compatible
                                                  with any cable tray system, channel systems can be more economical than conduit
                                                  in applications like communication, fire alarm, or call station and clock cabling.

                                                  WIRE BASKET
                                                  Produced from high-strength steel wires, a wire basket is a lightweight welded mesh
                                                  cable management system that provides superior flexibility and ease of installation.
                                                  This is usually best for maneuvering around obstacles. Low-voltage telecom cables,
                                                  control cables, and AV cables are traditionally installed in wire basket cable trays.

                                               Codes and standards must be considered in advance. For instance, NEC 392.10
                                               contains requirements on types of cable tray, cable size, cable types, and cable
                                               spacing that must be used.




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