Product Information: The air pressure switch is a safety mechanism which checks the fan is working correctly. It ensures that, if the fan fails within the boiler, there would not be a build up of toxic fumes with no means of venting them. The PCB closely monitors the air pressure switch to make sure it is fully functional before the unit is fired up, preventing the appliance from starting without one of its key safety devices.
This part is present in 3 different boilers in the Worcester range including the Worcester CBI 19/24 FON, CBI 19/24 FOP, CDI 24 .