i take it you mean it trips the switch on your fuse board? this will no doubt be your RCD, if so then you have an earth leakage fault. you will need to check your appliance to see if R1 and R2 phases are going to ground. you can quickly check to see if it is your appliance by plugging it into a three core extension cable and plugging that into a different socket / circuit and see if it still trips the RCD. if yes its the above if not you need to have the circuit checked for polarity loop impedance and insulation. all can cause an unbalance in the RCD coil triggering it to show a fault.
pete, August 2011
