A typical cable‑tray expansion joint can accommodate 20 mm of movement (safety factor included). Lmax=Joint capacity/Expansion per metre For projects where the historical extreme temperature difference is known, select the spacing accordingly. ” In 1993 NEC Article 318 there are no requirements for the handling of the thermal contraction and expansion of cable tray. A rung spacing of 6 to 9 inches (150 to 230 mm) is preferable when the cable tray cont d for instrumentation and control applications that require additional protec eferred to support and protect numerous small. us-trations without notice. All illustrations, descriptions and technical information included in this document are provided as indications and can cable trays are equivalent. The mechanical and electrical characteristics, tests, certifications, overall quality management, recommendations mentioned. Steel cable trays, like all metallic structures, undergo dimensional changes when subjected to ambient temperature variations., desert, cold storage adjacent zones), thermal expansion and contraction become critical design. Cable tray (or cable ladder) systems are a popular alternative to electrical conduit systems, as they have an outstanding record for dependable service, design flexibility and cost savings in commercial and industrial applications. A properly designed and installed cable tray system will provide. Is there anywhere else in the NEC book that says cable tray has to have an expansion splice plate every so many feet? Alls I have found is 392.
