Requirements for flat steel inside cable trays

Flat steel in cable trays must be installed according to NEC 392 and IEC 61537 standards, ensuring proper support, grounding, spacing, and load capacity.Material and Tray SelectionFlat steel cable trays should be made of steel or stainless steel with appropriate corrosion protection, such as galvanization or powder coating, depending on environmental conditions (indoor, outdoor, or corrosive environments) . The tray type—solid, ventilated, or ladder—should be chosen based on cable type, heat dissipation needs, and mechanical load .Mechanical Strength and SupportThe tray must support the weight of cables without excessive deflection. IEC 61537 specifies load testing to ensure trays can handle the expected cable weight and environmental forces . Supports, such as wall brackets, suspended supports, or center suspensions, should be installed at intervals recommended by the manufacturer, typically every 1.5 to 3 meters for ladder or solid trays . Rung spacing for ladder trays is usually 150–230 mm (6–9 inches) to prevent cable sagging .Grounding and Electrical ContinuityMetallic flat steel trays can serve as equipment grounding conductors (EGC) if they meet NEC requirements. All tray sections must maintain electrical continuity, with bonding jumpers installed at joints or bends to ensure a reliable grounding path .Cable Fill and SeparationFill limits: Power cables should not exceed 40% of the tray cross-sectional area; control or instrumentation cables can occupy up to 50% .Separation: High-power and low-power cables must be separated to prevent electromagnetic interference (EMI) . Barrier strips or separate trays may be used for sensitive instrumentation cables .Installation PracticesMaintain minimum vertical clearance of 12 inches above trays for maintenance access .Avoid installing trays in hoistways or enclosed spaces; trays must remain accessible .Use sunlight-resistant cables and expansion splice plates for outdoor installations to accommodate thermal expansion .Ensure proper ventilation in solid-bottom trays to prevent overheating .Compliance and SafetyAll installations should comply with NEC 392 (for U.S. installations) and IEC 61537 (international standard) to ensure mechanical integrity, fire resistance, and long-term reliability . Following these standards minimizes risks such as overheating, fire, mechanical failure, and electrical hazards. By adhering to these requirements, flat steel cable trays can provide safe, durable, and code-compliant support for electrical and communication cables in industrial and commercial facilities.