I had never thought about this until now, but our humidifer is installed on the cold air return BEFORE the filter. How much of the water vapor makes it through the filter and into the house?

Thursday, December 23, 2010 by Aprilaire Team
Consumer question:

I had never thought about this until now, but our humidifer is installed on the cold air return  BEFORE the filter.   How much of the water vapor makes it through the filter and into the house?   Do we need to adjust the humidistat setting differently because of this?  Thanks.


Aprilaires' response:


Proper installation of the #440 humidifier allows for it to be installed either on the hot air supply or cold air return. 

The way this works is that the static pressure of the furnace will blow the hot air through the bypass, into and through the water panel... this will of course evaporate the water that is held there and put the humidity into the main air flow.  This will put it through the filter and into the furnace back into the home.

The amount of moisture that is put into the air, remains the same as it passes through the filter and gets heated up, and goes into the home.  This is how we have humidified homes since 1954.

Now, in the summertime, you will get up to 60% or more humidity in your home..... this will pass through the same filter as you run your air conditioner.  Our units only create 45%, so since there is no harm to the filter with the higher levels of RH, our will be fine as well.  Also, no moisture will be held in the filtering system for your furnace.

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