Variac wiring | Physics Forums wwwicsforums›Engineering›Electrical EngineeringJun 15, 2009I think that the Variac can be wired for either 125 or 220 volt input, on the terminals in center picture. The label very clearly shows this. The common for either is the tab with the "0". Variac Wiring Diagram | Free Wiring Diagram Collection of variac wiring diagram. A wiring diagram is a simplified conventional photographic depiction of an electric circuit. It reveals the components of the circuit as simplified shapes, as well as the power as well as signal connections in between the devices.