If provisions for the thermal contraction and expansion of the cable trays are not provided for where there are large summer to winter temperature extremes (example: roof top installations); there is the potential for the cable trays to tear loose from their supports, for the. If provisions for the thermal contraction and expansion of the cable trays are not provided for where there are large summer to winter temperature extremes (example: roof top installations); there is the potential for the cable trays to tear loose from their supports, for the. 1993 NEC Section 300-7 (b) states that “Raceways shall be provided with expansion joints where necessary to compensate for the thermal expansion or contraction. ” In 1993 NEC Article 318 there are no requirements for the handling of the thermal contraction and expansion of cable tray. This subject. The Cable Tray Institute is now making available our complete library of technical articles which have appeared in the Cablegram. Cable trays have no space to flex, and may bend or break bolts. In this guide, the expansion gaps are explained to be calculated, as well as how to select materials such as aluminum or steel. We aim to ensure your project remains secure and does not breach the NEMA standards, causing it to suffer. e tray system. This paper examines the causes, implications, and mitigation of thermal dynamic stress in metallic cable tray systems, focusing on thermal expansion and contraction, the resulting internal stresses, and potential damage to both the t ay and cables.
