I have a house that is appx 3000 sq ft. The bubilder put in 2 furnaces 1 for the upper level and one for the lower. I would like to get a humidifer but don't know if I need 2 (1 for ea furnace ) or if I just put one on one of the furnaces
Thanks

Why not start with one? Perhaps upstairs where you sleep. I am sure some of the added moisture will work its way down stairs. If it is still too dry downstairs, you can always add a second one later.