Not a dumb question at all. My new house had 2 AC/Furnaces. They had
non descript filters without arrows when I moved in. I basically
looked at the ductwork and realized that the returns were coming down
adn going to the main unit and the filter was in between the two.
Therefore I put them in with the arrows pointing towards the main unit.
I also figured that while air quality is important, Carrier would want
to protect their equipment from the dirt and whatnot, so it would
probably be before the main unit. Hope that makes sense...it did to me
when I first started writing it. :-)