Originally, This was a 7 wire set up; but, I changed out the York, with a Goodman 5 wire heat pump, and kept the York air handler. The (X) @ t-stat, is wired to W2,with W at the outdoor unit the (W) @ t-stat is wired to W1, I put a jumper between W1 & W2. (O) is with O, (Y) is with Y, (G) is with G, (B) is with B, and one wire is clipped. I tested it in heat pump, with t-stat 5 deg. above rm. temp., it came on with compressor, and aux heat light on, then backed off to 1 deg. above rm. temp, aux light, went off compressor still running. Then turned system to Emergency heat; Light is on, no compressor. I think it's doing what it should be doing, but, wanted someone to help me understand the function of it, better than I currently do.