The Root Cause Of Fires Caused By Overheated Wall Switches

The internal contacts of Wall Switch will generate contact resistance during frequent switching. When an oxide layer forms on the contact surface or the spring pressure weakens, the contact resistance increases significantly, and the Joule heat generated when current flows increases exponentially. If a switch is not maintained after long-term operation, contact erosion can create a vicious cycle—increased resistance leads to increased heating, and high temperatures further accelerate the deterioration of the contact material.

Exceeding the switch's rated capacity is another contributing factor. High-power appliances such as household air conditioners and electric water heaters directly connected to ordinary lighting switches cause continuous overload current, resulting in a sustained rise in the temperature of the internal conductors and terminal blocks. The plastic casing material begins to soften above 80°C, reducing its insulation performance. When the temperature exceeds the critical point of 120°C, the casing may carbonize and smolder.