Method for heating a tank

A method for heating liquid in a tank, the method comprising:

• providing at least one Positive Temperature Coefficient (PTC) heating element;
• providing a pulse width modulation regulator;
• measuring parameters including a temperature of the liquid and a voltage applied across terminals of each of the at least one PTC heating element;
• heating the liquid without regulation, with a duty cycle of 1 or 100% of the pulse width modulation setting, insofar as the temperature of the liquid is below a first threshold temperature;
• applying pulse width modulation regulation to an electrical supply to each of the at least one PTC heating element for which the supply voltage exceeds a predetermined threshold insofar as a measured temperature is above a second threshold temperature, said second threshold temperature being determined as a function of measured parameters;
• and
• determining a modulation duty cycle for modulation of the electrical supply to each of the at least one PTC heating element and transitioning progressively from the duty cycle of 1 to the determined duty cycle.