How do you use 120V equipment on 240V?

See DEFINITIONS of ELECTRICAL TERMS for definitions of Amps, Volts, Watts, Ohms, etc. Our photo at left shows the data tag inside of a pump pressure control switch and shows that the switch might be wired for either 120V or 240V if other site conditions and equipment specifications permit. The pump pressure control switch in our photo at left has contacts that permit it to be wired to operate at either 120V or 240V. But we don't know if the pump motor itself can run at either voltage.

First make sure that the pump motor and control are labeled to indicate that either voltage level is permitted with the equipment you have installed. Second we don't know that the pump motor, even if it can run at 240V, will not also require a heavier-duty pump control switch than this relay. Second, there will be some additional costs when changing the voltage level at which an electric motor is going to be operated.

Even if the electrical wires can be left un-changed (when moving UP from 120V to 240V) the overcurrent protection (circuit breaker or fuses) will need to be changed to properly and safely protect the electrical circuit. In either case, if we exceed the current rating of an electrical wire, it will get hot, risking a fire. That's why we use fuse devices (or modern circuit breakers), to limit the current flow on electrical conductors to a safe level to avoid overheating and fires.

Some but possibly not all motor controls such as well pump control switches can be re-wired to operate at either voltage. But if not you'll need to replace the pump control switch.