Hi;

I had an April Aire 650 Whole House humidifier installed in my house.
It is a bypass model. They ran a thermocouple outside and I am not
quite grasping why. I am not questioning the install, I am just trying
to understand the concept. I can see where the unit would like to know
the temperature of the air so it can figure out the relative humidity,
but to take that reading outside doesn't seem logical since it is
using the return air in the house. It would seem to make more sense to
me to place the thermocouple in the return air duct. Am I missing
something? Please explain if you have the time.

Thanks
Pat