What does the interlock switch do in a furnace?

The interlock switch serves a critical safety function in a furnace. Its primary role is to ensure that the furnace cannot operate when the access door is removed. This is important because accessing internal components of the furnace while it is operational can pose serious risks, including electrical hazards or exposure to hot surfaces. By preventing the furnace from operating with the door off, the interlock switch helps protect technicians and homeowners alike from potential injuries.

In contrast to the other functions, such as regulating fuel supply or controlling ignition sequences, the interlock switch's design is specifically aimed at enhancing safety by ensuring that the furnace remains inoperable until it is safe to operate again. This aspect reinforces the overall safety protocols associated with furnace operation and maintenance.