April Aire Humidifier Installation Question

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
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The sensor tells the unit how cold it is outside. When it gets very cold line -20 you don't want the interior humidity to be as high as you might want it when it is say 40. If you tried to maintain 60% humidity when it is -20 outside, you would tend to get a lot of moisture freezing on windows, condensing in wall insulation etc.

--
Joseph Meehan

Dia \'s Muire duit
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You go Joe :-)
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I was going to say the same thing! Bravo Meester Meehan.
I've had to explain that to a lot of customers, but methinks I will just print your answer out on little cards...
;-]
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wrote:

It's usual practice to lower the relative humidity inside as the outside temperature drops. This is to minimize the chance that you'll have condensation form on windows, or worse, inside walls due to air leaks through the walls and insulation. My humidifier has a manual control with instructions to set it based on outside temperature. You apparently have a model that makes the adjustment automatically.
The actual humidity level is controlled by a humidistat in the supply air duct (usually), so there is no need to measure the return air temp.
HTH,
Paul F.
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Thanks to both of you for clearing that up :-)
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You set the unit till you see condensation somewhere, usualy on glass, then back it off till there is no condensation and leave that setting, it tracks the right amount of moisture you can have based on outside temp so no damage occurs to your home from over humidifying, which leads to mold and rot. You have a great humidifier.
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