The Potterton air pressure switch is a safety device which checks if the fan is fully operational. It ensures that, if the fan fails within the boiler, there will not be a build-up of noxious gases with no means of extracting them safely.
Voltage is 125
Technical specification
TypeAir Pressure SwitchCompatible WithSuprima 50 LManufacturer Model No5105576Brand NamePotterton