Metal becomes bigger when hot and smaller when cold. In this guide, the expansion gaps are explained to be calculated, as well as how to select materials such as aluminum or steel. All materials expand and contract due to temperature changes. It is important that cable tray installations incorporate features which provide adequate compensation for their thermal contraction and expansion. 1993 NEC Section 300-7 (b) states that “Raceways shall be provided with expansion joints. maintain spacing or to keep cables in place when the tray is ect the minimum bend ra-dius for cables as they exit the bottom of the cable tray. We aim to ensure your project remains secure and does. Steel cable trays, like all metallic structures, undergo dimensional changes when subjected to ambient temperature variations.