e switch enables safety protocols to check the fan is fully operational. It ensures that, if the fan fails within the boiler, there would not be a build up of noxious gases with no means of venting them. The PCB closely monitors the air pressure switch to make sure it is in full working order before the unit is fired up, preventing the appliance from starting without one of its key safety features.
This part is present in 3 different boilers in the Worcester range including the Worcester CDI 24 , CDI 24 , 24SBI NG .