Float Switch Motor Pump Control

Pumping of water into a tank is accomplished by motor operation. When the tank is about to be full with water, the motor pump is about to stops to operate. When the tank is about to be emptied, the motor pump will start to operate.

Float Switch Motor Pump Control Operation

Figure below (A) shows a tank half filled with water. The motor pump M at idle condition. Water flows out from the gate valve L. Lever C is tilted downward to the right because of the weight W1. Mercury B is at the right position inside the glass container A. the metal rods X and Y inside the sealed glass container A are at open condition. Float bulb K float over the water J inside the tank. Float bulb K goes down as the water drops down.

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(A) Water is withdrawn from the tank. Water level drops downward.

When the water level drops down beyond the stopper E, Figure below (B) the stopper E prevents float bulb K to go down further. When the water level goes down further weight W2 the effect of the combined weight of float bulb K and weight W2 is greater than the weight of W1. this effect will cause the lever C together with the glass container A to tilt down to the left side. The mercury inside the glass container will transfer down to the right. Metal rod X and Y will be shorted by the mercury B.  The contactor M (motor pump M), terminal Y, mercury B, terminal X, and finally to L2. The motor pump M will now pump water into the tank.

(B) Motor pump M starts to operate when water level reaches the bottom level.

As the motor pump M continue to pump water into the tank. Lever C remains tilted down to the left and water rises up together with float bulb K, see figure below (C).

(C) Water level in the tank continue to rise up as the motor pump M pump water in the tank.

When the float bulb K reaches the stopper F, it will stop sliding from string G but it will still continue to rise up and will lift weight W2, see figure below (D) Since float bulb K is lifting weight W2, the weight is carried by string G is practically zero. The pull on the right side of the lever C due to weight W1 is now greater than the pull at the left side which is the weight carried by string G. The lever C where therefore tilt down to the right. This will also cause the mercury B will remove the shorting of terminal X and Y and cause the motor M to be de-energized and stop the pumping water into the tank.

(D) Motor pump M stop to operate as the water in the tank reaches the top most level.

To completely stop the operation of the Float Switch Motor Pump, the toggle switch SW is switch OFF.

 (E) The complete control circuit of the Float Switch Motor Pump Control.

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