Methods and devices for controlling a welding power source based on a primary supply voltage level are provided. One method may include sensing activation of the welding power source and sensing a primary supply voltage established on a control transformer of the welding power source. The method may also include establishing a substantial current draw from a primary power supply that exceeds a predefined current threshold when the sensed primary supply voltage exceeds a predefined voltage threshold. The substantial current draw may be adapted to trip a circuit breaker of the welding power source to disallow current through the welding power source when the sensed primary supply voltage exceeds the predefined voltage threshold.