you can, but only if 1 is on at a time (relays, relays), the ballast will have a shorter life if properly modified to run hps and mh (disable the starter for the mh). Just get another ballast.
4x5 Reviewed by 4x5 on . Lighting Question Hi, Can you use 1 ballast to control 2 lights. Like if I use a spliter to control an HPS and an MH light (both 250w). I am not sure if this is possible. From reading through the forums I think everyone who uses a HPS and MH lights during the flowering use 2 different ballasts? :wtf: Rating: 5