Can only cables be placed in cable trays

Cable trays are primarily designed to support cables, but only certain types of cables rated for tray use are permitted, and other components like conduits or non-cable items are generally not allowed.Cable Tray UsageCable trays are open support systems used to route and organize electrical wiring in industrial, commercial, and data center environments. They are not raceways; unlike conduits, they do not fully enclose wires, so the cables must have durable insulation and be rated for exposure in a tray system . Only UL-listed, cable tray-rated cables such as Type TC (Tray Cable) or metal-clad (MC) cables are typically allowed . These cables are designed to withstand mechanical stress, heat, and potential exposure in the tray.Restrictions and RequirementsSingle-conductor cables smaller than 1/0 AWG are generally not allowed unless specific industrial conditions are met .High-power and low-power cables must be separated to prevent electromagnetic interference (EMI), often using barriers or separate trays .Cable trays must remain open and accessible; they cannot be permanently enclosed, and fire-stopping measures are required if they pass through walls .Non-cable items, such as conduits, piping, or equipment, are not permitted inside the tray, as this can compromise safety, heat dissipation, and compliance with NEC standards .Practical ConsiderationsTray types (ladder, ventilated trough, solid-bottom) affect cable selection and fill limits. Ladder trays are preferred for heavy power cables due to ventilation, while solid-bottom trays provide EMI shielding but reduce heat dissipation .Outdoor or sunlight-exposed installations require sunlight-resistant cables and may use expansion splice plates to accommodate thermal expansion .Cable fill limits must be observed: typically 40% for power cables and 50% for control cables of the tray's cross-sectional area .ConclusionCable trays are intended exclusively for cables that are rated for tray use, such as Type TC or MC cables. Other components, including conduits, piping, or non-rated wiring, should not be placed inside the tray. Following NEC Article 392 ensures safety, proper heat management, and compliance with electrical codes .