Must cables in underground parking garages be installed in cable trays

Cables in underground parking garages are not strictly required to be installed in cable trays; they can also be installed in conduits such as threaded rigid metal or intermediate metal conduit according to NEC standards.Cable Tray UsageCable trays are widely used in underground garages for organized, accessible, and safe routing of electrical, communication, and control cables. They provide open-air support, simplify maintenance, and reduce hazards like overheating or mechanical damage (Qiongkai Global) . Cable trays come in various types—ladder, trough, solid-bottom, and wire mesh—each suited for different cable loads and environmental conditions . They are particularly advantageous in areas where access for inspection and modifications is needed (Cable Tray Institute) .NEC RequirementsAccording to NEC Article 392, cable trays are a support system for electrical conductors but are not the only approved method for cable installation. Only conductors rated for open-air environments, such as Tray Rated (Type TC) or Metal-Clad (Type MC) cables, should be used in trays, and proper clearances and fill limits must be maintained . Cable trays are prohibited in enclosed spaces or hoistways and must remain accessible . For underground wiring specifically, NEC Section 511.8 requires that cables below Class I locations in commercial garages be installed in threaded rigid metal conduit or intermediate metal conduit. Exceptions allow PVC, RTRC, or HDPE conduits if buried under at least 600 mm (2 ft) of cover, but the last 600 mm of the run must use metal conduit with an equipment grounding conductor . This indicates that cable trays are not mandatory for underground runs, and conduits are the standard method for buried or hazardous locations.Practical ConsiderationsWhile cable trays are excellent for above-ground, accessible areas of a garage, underground or buried sections typically require conduit systems to protect cables from moisture, mechanical damage, and corrosion. Cable trays may still be used in accessible subterranean areas where maintenance access is feasible, but they are not a code requirement for all underground installations .ConclusionCables in underground parking garages do not have to be installed in cable trays. Cable trays are optional and mainly used for accessible areas where organization and maintenance are priorities. For underground or buried runs, metal or approved nonmetallic conduits are required by NEC Section 511.8, ensuring safety, grounding, and compliance with electrical codes. Proper selection depends on environmental conditions, accessibility, and the type of cables being installed.