This pressure switch signals the pump to start when the water system drops to 30 PSI (factory set) and stops at 50 PSI (factory set). This switch is to be used with submersible well or jet pumps. It can be wired 115-Volt or 230-Volt. This switch must be used in conjunction with a well pressure tank. The air pressure in the well tank, when empty of all water, must be set to 28 PSI, or the switch will not operate properly. This switch is equipped with a low-level cut-off arm that automatically shuts off a well pump when there is a dramatic decrease in pressure, such as a leak in the discharge pipes or a faulty pressure tank.