Mar 062014
 

In industry various devices and systems are used to regulate liquid levels – electronic, electrical, mercury, electromechanical and mechanical. Electronic ones are the most accurate, but their price is relatively high, and in most cases the tolerance of the controller allows some deviation. One of the controllers that is most widely used in the household and industry is the electric liquid level controller with a float and weight. Its simple structure, easy connection and smooth operation make this device preferred for level controlling of tanks.

original_30438
In the picture, the yellow cylindrical body is the weight, and the yellow-blue one is the float. In the body, acting as a load, there is an axial opening through which the cable passes. Depending on the location of the weight along the cable, the distance between it and the float changes, and therefore the arm of the movement of the float changes, too. In this way there is an adjustment of the limiting maximum level and when it is reached the controller turns off the pump. When placing it, we must observe that the limiting minimum level at which the level controller must turn on the pump and the tank begins to fill, is 0.2m from the bottom.

Another prerequisite is that the diameter of the tank, if circular or its width, if it has a rectangular section, must not be less than 0.6m. The total cable length is 2m. The temperature of the regulated liquid must not be less than 0 ° C and must not exceed 50 ° C. The liquid must not be touched when the level controller is plugged in the circuit. When connected to the mains, use 30 mA RCDs

original_44615An example where the level controller is used to protect the pump against „dry running“ and turning off at set at counterweight level.

The liquid level controller is particularly useful for submersible pumps which break down if running dry because there is no water to cool them. Connecting a level controller to the pump does not allow that to happen.
The electrical connection can be done in 3 different ways:

Option I- with function of filling the tank.
The blue wire of the level controller is connected to the phase wire of the electric pump, and the black one – to the neutral of the installation (the brown wire is insulated). After switching on the pump via a starter, it starts to fill the tank with water or other liquid. When the water reaches a preset level, the float opens the normally closed contact and switches off the pump. During this operation the pump is switched on manually.

Option II – with function of emptying the tank
The brown wire of the level controller is connected to the phase wire of the electric pump, and the black one – to the neutral of the installation (the blue wire is insulated). Upon opening a valve at the bottom of the tank with the purpose of using the water (or liquid), the level begins to drop. When the water reaches a preset limiting minimal level, the normally open contact of the level controller closes and switches on the pump. During this operation the emptying is done manually.

Float-Switch---9008

Option III with function of automatic filling and emptying the tank

Here the brown wire is connected to the phase of the pump, and the blue one to the phase of a solenoid valve located at the bottom of the tank. The black wire is connected to the neutral of the installation. When power is fed to the circuit, the pump will fill the container until it reaches the limiting maximum level and the float will open the normally closed contact, thereby closing the normally open contact and a voltage is fed to the solenoid valve, which starts emptying the container. A second pump can be used, instead of valve, to draw water from the container. The process will end when the electricity in the circuit is cut off.

variant IIIwith function of automatic filling and emptying the tank with fluid

The liquid level controller is used wherever there is a need to manage the process of filling and emptying tanks for water and other liquids such as pools, wells, small purification facilities, etc. Its simple structure and low cost make it a desirable and reliable tool for many activities where it is necessary to control the level of liquids.

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