What switch disconnects all electrical power supply to the furnace?

The interlock switch is designed to disconnect all electrical power supply to the furnace, ensuring safety during maintenance or when accessing components of the furnace. This type of switch ensures that the system cannot operate while someone is working on it, preventing accidents and potential injuries.

In the context of furnaces, the interlock switch plays a vital role in various safety protocols. It typically functions in conjunction with other safety devices, ensuring that if the furnace is opened for servicing, it cannot be inadvertently powered on until the components are properly secured. This crucial safety mechanism protects both the equipment and the personnel handling it.

The other options serve specific functions within the furnace but do not disconnect all electrical power. The pressure switch, for instance, monitors the pressure within the system and can disable the operation if the pressure is outside normal boundaries, but it does not cut all power supply. The operating switch controls the operation of the furnace, while the igniter switch is specifically for activating the igniter. Each of these has a specific role, but only the interlock switch provides the comprehensive disconnection of power necessary for safety.