Heating element and circuit breaker tripping

My Hoover AL 120 is somehow tripping the circuit breakers when it starts working, even if the temperature is set to 0º. If I disconnect the right connection of the heating element, it works just fine with cold water, if I disconnect only the left heater connection, breakers goes off. I've checked for shorts to chassis (no shorts found), heating resistance is around 30 Ohms, witch i assume is good (7.5Amps, about 1800W@230VAC). Temperature potentiometer has no effect (connected or unconnected). I have no idea what can be causing this issue (main board? mains filter? ... ?)