The resistance power and the tank filling, are controlled by two NTC and a pressure switch (model dependent), whose data are evaluated by the PCB.
After switching on the unit, first checks if there is enough water in the boiler. To do this, feeds the resistance. If the tank is empty, the temperature of the air inside rises quickly. When NTC1 temperature reaches 190ºC, the resistance power is cut off and the pump starts for 6 seconds to ensure that the resistance is below the water level.