The float, which is connected to the switch assembly, rises when condensate enters the receiver tank. When the float rises above its set point, it energizes the motor on the pump. Once started, the pump will continue to run until the water level drops below the bottom position of the float switch.
There it will de-energize the motor to shut off the pump. This cycle repeats as condensate begins to fill the receiver tank. On duplex systems, the float switch is replaced with a Mechanical Alternator-Switch connected to a float. The Mechanical Alternator cycles used between the two pumps, allowing only one pump to run at a time under normal conditions. If the condensate reaches a high water level, both pumps will be activated.