Can someone tell me how often you should change a furnace filter? I am a new home owner and am clueless. Has anyone ever used Aprilaire filters?
Thank you very much in advance.
Hi @mikecj,
It would depend on how much work the filter has to do. How dirty the air is that it filters / the type of filter being used.
Maybe visually inspect it monthly and change it when it looks dirty? or every 10,000 miles, which ever occurs first. 
A differential pressure switch hooked to an HRDS1?
JOD.
Hah… well done. This is an automation forum, after all…