A copper run must cross the space above a drop ceiling that is used as an air return. Which cable rating belongs in that space?
Select an answer to reveal the explanation.
Short Explanation
You’re routing cable through the building’s air-return path, so you need a jacket made for that space. Plenum-rated cable is the right fit; riser-rated cable is for vertical runs, direct-burial cable is for underground use, and shielding does not give a cable an air-return rating.
Full Explanation
Plenum-rated cable has a jacket intended for air-handling spaces, including the air return above a drop ceiling, so it is the rating this run needs. Riser-rated cable is intended for vertical runs between floors; that rating does not qualify it for an air return. Direct-burial cable is built for underground moisture and soil, not for a ceiling space. Shielding reduces electrical interference, but foil or braid is not a jacket rating for an air-handling space, so shielded cable of any jacket is not the requirement. Exam caveat: patch cords in the room can be ordinary; the requirement follows the cable that actually enters the air return. For a practical check, read the jacket print on the reel before the pull, confirm it says plenum-rated, and keep that cable in the air-return portion of the run. Do not substitute the riser-rated cable already on the cart. Photograph the jacket print where the cable enters the ceiling so the rating is on record.