PURPOSE: To facilitate maintenance by dispensing with a level sensor and a cable for the sensor.
CONSTITUTION: In a comparator 15, an actual current value, which is detected by a detector 10, of a pumping motor 2 and the reference current value predetermined in a setting device 13 are compared with each other, and a signal is outputted to a timer 16 when the actual current value of the pumping motor 2 is reduced because of idle running of the pumping pump 1 due to water shortage and the difference between the actual current value and the reference current value reaches the predetermined range. During the duration set in the setting device 14, the timer 16 excites an operation coil 17a when an output of the comparator 15 continues. According to excitation of the coil 17a, a switch 17 is opened and the operation coil 11a is released from excitation, and consequently, the switch 11 is opened and the pumping motor 2 is stopped.
JPH01138384A | 1989-05-31 | |||
JPH03282000A | 1991-12-12 | |||
JP2092082B |