What is the APS?
A boiler air pressure switch, also referred to as the pressure safeguard acts as a safety mechanism that checks the fan is in full working order. It ensures that, if the fan fails within the boiler, there would not be a build up of toxic gasses with no means of venting them. The PCB (Printed circuit board) closely monitors the air pressure switch to make sure it is fully operational before the boiler is fired up, preventing the appliance from starting without one of its key safety devices. Popular boiler air pressure switches fitted are manufactured by Honeywell, Yamatake, Dungs and Huba.