I recently purchased a home with a whole house humidifier hooked into
the furnace. It has a humidistat control, which I have set according
to the recommended humidity setting for the current outdoor temp.
There is also a dial on the humidifier unit itself with high/medium/
low settings. Does anyone know what this is used for, or what it
should be set to? The dial is a half circle, with settings in the
From the settings and order you cite, this "dial" sound more like a duct
damper. "Hi" = full open; "Low"= full closed, etc.
Is there a 3" or 4" flexible duct from the humidifier back to the furnace
plenum or cold air return?
If so, the humidistat senses the humidity level and turns the unit on and
off. The "dial" controls the opening to the furnace air supply. In some
cases having the air supply wide open can allow unevaporated water to enter
the furnace and cause mineral build up and/or erosion. On the other hand,
setting the air supply too "Low" can keep the humidifier from getting enough
humidified air into the house.
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