You need to do 4 things to prepare your furnace mounted humidifier for the heating season.

#1 Replace the media filter found inside the humidifier

#2 Turn the bypass damper in the 6″ round pipe to the “winter” or “open” position

#3 Open the water valve (follow small copper tube from the humidifier to where it connects to your water pipes)

#4 Turn the Humidistat from “off” to “40%” or “6″ or another position used in the past (there are a number of controls “Humidistats” used with many different settings)

Lastly, do a visual inspection of the water drain hose connected to the bottom of the Humidifier, replace if it is blocked with dirt