The baseline rule is straightforward: Type TC cable can be used for power, lighting, control, and signal circuits in cable trays (including trays with mechanically discontinuous segments up to one foot), raceways, and conduit. Between lighting, switchgear, conduit, and the hundred other line items that make up a typical project BOM, tray cable is probably not the product category keeping you up at night. And it shouldn't be that's what your master distributor is for. But here is where tray cable does demand a few minutes. Question 1: Can mechanical utility piping or tubing containing water or compressed air be installed in cable trays with electrical cables? Answer: No. Cable trays are a support system for electrical cables, power, signal, and communication and optical fiber cables.