Chilled water coils — These coils have headers precisely sized to mini-mize water pressure loss. Chilled water coils are manufactured of 1/ 2-in. OD (5/ 8-in. OD optional) copper tubes with aluminum plate fins (8, 11, or 14 fins per in.). Copper and e-coated fins are optional.Perfect, medium and bypass face area coils are available in 4, 6, 8