Reservoir level control

Automatic hydraulic systems are part of several industrial plants, but due to population growth and water crises automatic systems for water storage, reuse and abstraction have become increasingly common in residential installations. Whether in large cities or rural properties, these systems have occupied their space and should be included in the portfolio of electricians’ jobs, either for the construction of automatic level systems or for their maintenance.

There are several configurations for level control systems, the most common of which is the use of two-level sensors to activate a water pump.

The level sensor is a small float with an electrical contact encapsulated inside it, it basically works as a switch, allowing or not the passage of electric current between your contacts. Attached to the side of a reservoir or even to a pipe system inserted into this reservoir, it can be used as an open or closed contact for the electrical control of a pump.

For the automatic level control system of a reservoir, the following materials are used:

  • 2 level sensors;
  • 1 contactor (compatible with the power of the pump to be connected);
  • 1 Electric water pump.

The electrical diagram below represents the connection of the cables for this circuit.

Automatic level control system.


In this system, two-level sensors control the maximum and minimum level of liquid inside the reservoir. Both sensors in this command are used as normally open contacts. With the reservoir full, both sensors are open and the pump is off.

When the liquid level starts to drop and passes through the first sensor (maximum liquid level sensor) it closes but the pump is not yet started because the second sensor (minimum liquid level sensor) is not closed yet, the pump remains deligated. The moment the liquid is below the minimum level, the second sensor closes, allowing the contractor to have power in its coils and in this way the pump starts.

The normally open contact of the contactor is in parallel with this sensor system as a seal contact, so when the level starts to rise, due to the liquid that the pump is injecting into the reservoir, the pump is not switched off even with the sensor minimum level of the open liquid. Only after exceeding the maximum level and opening the maximum liquid level sensor, the seal contact is broken by turning off the pump.

The use of two sensors allows the system to be turned on and off with an interval of time that is regulated by the amount of liquid between the two levels of the sensors if only one sensor was used (as is the case of a d ‘box). common water with a float) there would be several shutdown ligaments in a row whenever the liquid started to drop and soon it would shut off when it started to rise. In this type of system, the service life of the engine would be severely reduced while the energy expenditure of the constant drives of the engine would be high.

Advantages of the system through level sensors.

This system has great advantages and one of the main ones is the low cost of installation, this sensor has a relatively low cost and a long duration having a useful life of thousands of drives.

The sensors are fixed on the side of the reservoir or are fixed in a fixed system, which guarantees excellent repeatability of the activation and deactivation level, which is not possible in float switch systems, for example, which may vary due to the undulation of the liquid on the surface of the tank. reservoir.

The same system can be used to drive any pump power, requiring only the correct contactor dimensioning for the pump, both in single-phase and three-phase systems