Many power-consuming devices such as single-phase motors are designed for dual-voltage operation. Figure 1 shows a solenoid valve with four different colored wires coming from its wire housing. Figure 2 is the wire housing cover that shows a technician how to connect the wires in order for the device to handle 120 V or 208-240 V.
Notice in Figure 2 that, for the solenoid to handle the lower voltage of 120 V, the red and blue wires would need to be connected, as would the black and yellow wires. 120-V power (120-V hot leg and a common) would then be brought to the wire bundles connected together. One bundle would receive the 120-V hot wire, and the other would receive the neutral wire. It makes no difference which one receives the hot or neutral wire.