Cable trays and busways at floor level or at slab penetrations shall have a waterstop no less than 50 mm in height. Sealing shall be tight and reliable. Cable tray installation must comply with specific technical standards to ensure electrical safety, system reliability, and long-term maintainability. Route. e 21, Subparagraph 2; Article 23, Subparagraph 1 and Subparagraph 2; and Article 157 shall apply. Separation by a fire barrier with a 3-hour rating. They provide robust support for cables while ensuring fire safety in extreme conditions. This guide explains the. Effective protection of cable systems around the world: our tried-and-tested FLAMMOTECT-A and DG-CR 0.