A "Normally Closed" float switch is generally used to signal high water level (either by triggering an alarm or by, say, turning off a pump that is being used to fill a reservoir). In other words, as the water level rises, this float switch flips up and opens the circuit (which cuts off power).
Our Normally Closed 120/230V Float Switch is a 15amp rated pump switch with heavy duty contacts for maximum pump starting loads.
You may also be interested in our Low Level Audible Tank Alarm which utilizes a Normally Closed Float Switch.