text: need help wiring a buck and boost transformer on a single phase application. 255v bucked down to 240? using federal pacific 2 kva buck and boost. trying to wire to buck voltage down on my phase converter. schematics are congfusing. thanks i remember that the auto xfmr (buck/boost) has standard input terminals then a series of terminals based on the voltage range you are looking for. look at the connection diagram shown on the link below.  you want to have the xfmr setup to figure c where you have input on h4 and x1/x3. the xfmr is jumpered between h3 to h2 and h1 to x4/x2. the output comes off of h4 and h1. h4 terminal would be considered common. monitor the output voltage using a trusty dvm, don't ever go by the info on the xfmr.