When installing two cable trays in parallel at the same height, the distance between them should be no less than 0. This spacing is crucial for adequate maintenance access, ease of inspection, and ensuring proper airflow for effective heat dissipation. The spacing between trays, whether horizontal or vertical, depends on various factors like cable type, environment, and tray material. These rules shall be applied in the cabling engineering workflow for all subjects concerning or in relationship with cabling in the ITER facility. Here's what you need to know: Cable Types: Only use. Hubbell Wiring Device-Kellems and Hubbell Premise Wiring are divisions of Hubbell Incorporated, a U. headquartered manufacturer with over 130 years of supplying solutions for the electrical and data markets.