Unipolar air in the corridor opened and tripped.

If there is leakage protection in the second stage and there is no leakage protection in the first and third stages, that is the problem of leakage. This is more difficult to check, it is estimated that the line will be changed! If all the switch functions are the same, look down!

The second stage is a little hot for two reasons: the capacity of the first stage switch is too small, so it can be changed. The connection between the incoming line and the outgoing line of the second switch is not good, or it is too loose, which leads to fever and needs to be reinstalled. Better call an electrician!