Vacuum Switch, 1/4 in BSP, 12/24 VDC

The vacuum switch is an electrical device wired into the power circuit to an electric motor or electric clutch. The switch is mounted on the inlet side of the pump, between the pump and the liquid source; it senses the break in vacuum when the pump runs out of liquid. The break in vacuum causes the switch to open the circuit and shut-off the motor or deactivate the clutch. The switch contains a spring loaded diaphragm sensitive to a vacuum of not less than 2-1/2 in Hg (mercury). The vacuum switch is generally installed in a pumping system when transferring or pumping a limited amount of liquid, when the pump cannot be attended at all times. The switch provides automatic shut-off when the pump runs dry, helping to prevent damage to the pump. Normally, the switch is manually restarted, although it is possible with electric motor and clutch installations to wire a momentary switch, float or liquid level device across the terminals of the vacuum switch to reactivate the system remotely or automatically.