| CPC H05B 1/0236 (2013.01) [F01N 11/00 (2013.01); F02M 31/125 (2013.01); H05B 1/0244 (2013.01); F01N 2610/02 (2013.01); F01N 2610/105 (2013.01); F01N 2610/1486 (2013.01); F01N 2900/1811 (2013.01); F01N 2900/1814 (2013.01); H05B 2203/02 (2013.01)] | 20 Claims |

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1. 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.
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