The one I linked can control the fan as well. It's good info that just running it when the furnace comes on is not enough time to properly humidify. I have an air exchanger as well. It actually has a dehumidifier they suggest using if you get moisture build up in it. Yeah right I don't think I have to worry about that

Here is a site I have been looking at with info about the Honeywell units. I appears to be some kind of training site.