Abstract: Disclosed is a control unit for welding apparatus which feeds wire in the presence of a shielding gas to a workpiece at different rates with different heat inputs in accordance with the wire feed rate. The control unit is designed so that through a single control element the workman may adjust the wire feed rate and simultaneously and automatically adjust the heat input. When different wire types are employed in different welding processes, adjustments in the control unit are provided that allow the workman to reset the relationship between the wire feed rate and heat input in accordance with the type of wire being used. A hot-start feature is provided so that more power is applied for a predetermined manually adjusted time period during start-up.