Product review (5 stars): 15 minute install. Whole-home humidifier now runs only when the fan is running.
Very easy to install with included instructions and diagram. Took me about 15 minutes. My only mistake was that originally I tried to loop the "fan" wire through this that is between the thermostat and the furnace control board. That's a very low current wire - you need to use the high current wire that goes between the furnace control board and the fan/blower motor itself to have enough current to trigger the relay. The instructions made that clear - just my mistake.