Pump Protector

This circuit has been developed to limit the running time of a sump pump, since the pump can be damaged if it runs too long when the sump is dry. The circuit detects how long the pump has been switched on, and if this time exceeds a previously set limit (30 minutes in this case), the supply voltage to the pump is interrupted.The protector circuit is connected in series with the pump’s mains supply cable. The 230-V input is on the left-hand side of the schematic diagram, and the output is on the right. The schematic diagram consists of three main elements: the power supply, the timing circuit and the in-use detector.