I'm new to this and wondering if someone can help me. I have a Rheem 90+ upflow furnace that's about 15 years old (Model #- RGRA-07EMAES). I'm going to be installing an Aprilaire 600M humidifier and there's one thing I'm unsure of at this point as far as the installation goes. According to the furnace paperwork there is a connection on the furnace's integrated control board where the humidifer can be connected to only allow water flow when the furnace blower is on. Can someone tell me how to find this? I'm sure its here if the manual says so, but I'm blind I guess. Of course, the alternative is to install a relay to the common hookup of the blower but I'd rather not if I don't have to.