Vertical distance between adjacent cable trays, measured from the bottom of upper tray to the bottom of the lower tray, shall be at least 400 mm. To avoid damage during cable laying, cable trays and accessories shall have no scales, abrasive, rough surfaces or cutting edges. This damage is often not apparent until post-installation cable testing. This is an inefficient and expensive way to do an. It is fairly well understood that if an assembly short-circuit current rating above 10,000 amperes is desired, a Power Distribution Block or a Terminal Block with a high short-circuit current rating must be utilized. However, there is great confusion concerning the spacing requirements of these. Conductor damage during installation is one consequence of undersizing junction and pull boxes. The size of the electrical gap directly affects the safety.
