7500W electric heating why always burn the air-opening

The open itself has a thermal protection function, the internal bimetal temperature reaches a certain value will be deformed, and then triggered the relevant institutions caused by the tripping. 7500W power, if calculated according to the 220V, it is 34.1A current, from this point of view does not reach the rated current of the air open, you check the air open the top and bottom of the wiring screws have been tightened, if it has been tightened and you have a clamp multimeter, then measure the actual current of the circuit is more than 60A, if not more than it should be a problem of the open itself. If you have tightened the upper and lower wiring screws, and you have a clamp multimeter, measure the circuit of the current is actually how big, whether more than 60A, if not more than, it should be open itself has a problem.