Why is the zero terminal of distribution box hot? What is the reason?

Terminal heating is mostly caused by large contact resistance. Unclean contact surface, fire caused by loose fasteners, and oxidation of contact surface will increase contact resistance, consume more contact power and increase temperature. Of course, the terminal is too small to bear large current, which is also one of the reasons. Generally, the neutral current in the three-phase distribution box should be less. If the three-phase load connected to the distribution box is seriously unbalanced, the neutral current will increase and the neutral line will heat up.