Fiberglass Cable Tray & Channel Selection Guide
Step 4 : Determine the cable load. Calculate in pounds per linear foot the load of the cables to be supported. Consider any extraneous loads such as ice, snow, wind, etc. and add this value to the cable load. Step 5 : Determine the tray style. Fiberglass cable tray offers two side rail configurations; "E" and "Z". Refer to the Structural Designs section of this catalog to determine tray style. Step 6 : Determine the support spacing. Normally, cable tray systems are supported at eight foot to twenty foot intervals. Tray may be supported by wall mount brackets, trapeze suspensions, supports from existing structures or it may be floor mounted to minimize deflection. Splice joints should be placed at or near the quarter point of the span. This guideline should be rigidly followed and non-compliance granted only after careful engineering analysis because of high cable tray stresses which can be generated. Step 7: Determine the NEMA or CSA load class. The cable tray system should be determined by the combination of cable load (Step 4) and support spacing (Step 6). Consult the Structural Designs section of this catalog or NEMA FG 1 to assist you in the selection of a tray system that meets your requirements. NEMA Class Working Load* A 50 lbs./lin. ft. B 75 lbs./lin. ft. C 100 lbs./lin. ft. * Working load classifications based on 20 foot support spans. Chart not applicable for channel tray.
Several criteria must be considered in selecting fiberglass cable tray for your application. Factors include load capacity and safety factor; support spans; deflection; cable diameter and tray fill capacity; application environment; space restrictions; fire resistance; future expansion and cost. Article 392 of the National Electric Code provides cable size and cable fill information. NEMA Standards Publication No. FG 1, Fiberglass Cable Tray Systems, specifies manufacturing standards, performance standards, load class designation specifications and application information such as support span guidelines and temperature deflection information. The following guidelines will assist you in your selection of fiberglass cable tray: Step 1: Determine the resin system required based on the application, location, and environment (consult the corrosion resistance guide in the Application Environments section). Fiberglass cable tray is available in polyester and vinyl ester resin systems. Vinyl ester provides more corrosion resistance than polyester in some environments. Step 2 : Determine tray loading depth and width. Depending on the size and number of cables needed, use the guidelines in NEC Article 392-8 through -12 to determine tray loading depth and width. Step 3 : Determine rung spacing. The smallest cable or wire bundle determines the rung spacing for ladder type trays. In general, use 18" rung spacing for 2" O.D. or larger, 9" or 12" rung spacing for cables from 1" to 2" O.D., 6" rung spacing for cables from 1⁄2" to 1" O.D. and fiberglass channel type trays for smaller cables.
GLAS - Selection Guide
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