Erby, Ok, let me try to understand this. Then the dryer could affect the burning operation of the furnace? I know most of the heat and humidity go out the vent, but not all, and if the unit is in a/c mode wouldn't the return be pulling the heat in, given the close vicinity? It's my understanding that the whole purpose of return air is so that the unit is recirculating warmer or cooler air, depending on mode set on, so that it doesn't have to work so hard all of the time cooling or heating the inside air. Myself, I'm in the learning mode, so am I in the ballpark or way out in left field? Mike meant the installer may have manufactured his own list in lieu of the manufacturer's listing. I think??? "You're never too old to learn, or to un-learn." Mike M