The main function of the knob switch is to play a temperature adjustment function. The explosion-proof knob switch is generally recommended to be installed in the junction box, because the outside of the explosion-proof junction box cannot be opened. However, if the seal is new, it is not good. If the seal is not good, it is very likely that the ideal temperature will not be met when heating. If it is not explosion-proof, the rotary switch can be installed on the top of the junction box, which is also convenient for operation.