The single-phase hermetic compressor has a fixed rotation of its electric motor. In three-phase applications rotation is very important. The compressor might have a directional oil pump that will not pump efficiently if it turns in the wrong direction. Rotation on three-phase motors may be reversed by reversing any two motor leads.
This can be done either at the motor starter or at the motor itself. It is easier to do at the starter or disconnect most of the time. Be careful not to cause trouble in another circuit or cause a cross-phasing. This occurs when you touch two phases together without a load circuit in between. Figure 3-12 shows a compressor being rung out, note the readings at the terminals.