The pumps are controlled by two differential pressure switches with adjustable calibration due to the electric control panel supplied with SM electronic card for:

- Sequential starting of the pumps
- Changeover of starting order
- Protection against dry running
- Adjustable timing from 0 to 180 seconds (three phase version)

When the system pressure reaches the closing value of the electric contact of pressure switch no1, the first pump starts. If the water consumption increases and the pressure goes down the second pump starts. When pressure increases the manostats open their contact switching off one of the pumps.

At the end of each cycle, the automatic inverter changes the starting order of the pumps (at the first cycle pressure switch no1 is associated to pump mo1; the next cycle to pump no2). In case of simultaneous closing of the two pressure switches, the electronic card delays the starting of the second pump avoiding strong pressure joltsand overload of the electric power supply.