Humidity control

Old 11-23-17, 09:17 AM
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Humidity control

I have an April Air humidifier attached to my cold air return at the main plenum located in the basement, along with a humidistat control in the same location. I usually set it at about 35% at a 20 degree or above outside temp setting and forget it. Of course the temp will change dramatically during the day and night and during the week, especially during this time of year.

Can I and would it be of any benefit to move the humidistat to the living quarters so as to make adjustments easier? And would I locate it at the thermostat? And could I just remove it from the plenum, extend the wires and cover the hole?
Old 11-23-17, 09:41 AM
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I'm not an hvac expert, but I will tell you what I know. You don't really play with the humidistat like you might with the thermostat. For one thing, it doesn't respond as quickly as the thermostat does. It can often take days for you to notice a measurable change. For that reason I don't think I would go to the extra work of moving the control upstairs.

IMO, I think you have the right idea. 35% is a reasonable setting, and if it gets colder and you notice a problem with condensation, you can turn it lower for a few weeks or months during the winter.

If you get a cold snap, say 0F, for a week, you might find that your humidity is still too high. (Condensation on windows and such) So you might turn your humidistat down. Problem is, it doesnt respond quickly- depending on how tight your house is, your humidity may to take days to decrease, and by the time it does, it's likely the weather will have changed.

Being a window guy, I have lots of conversations about sweating windows in the wintertime, and the problem is always with customers who set their humidistat too high and won't turn it down. Then they wonder why their windows are so wet when it's -10F outside. (Duh!)

Here is one guideline that I found online, based on University of Minnesota research, assuming a 70F indoor setting:

20 to 40F Not over 40%

10 to 20F Not over 35%

0 to 10F Not over 30%

-10 to 0F Not over 25%

-20 to –10F Not over 20%

-20F or below Not over 15%

Personally, I have never had a humidifier, and don't see the need for it.
Old 11-23-17, 09:50 AM
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WOW! Your answer pretty much reflects my way of thinking. And you reinforced my way of doing things. I guess I'll just keep things the way they are. Thanks.

Your remark about people complaining about sweating windows is spot on. At work I get the two extremes. Either it's way too dry and they don't want humidity or windows sweat and they won't turn down the humidifier.
Old 11-23-17, 12:28 PM
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A manual humidistat just controls based on local sensed humidity. The newer Aprilaire humidistat comes with an outside sensor and optimizes the setting based on outside temps.

My humidistat is on my return duct in the basement and I change it several times a week. I only strive to increase the humidity a few percent over ambient. Just enough to take the edge off the heated dry air. Many people try to approach unrealistic humidity levels in the winter. That's just being foolish.

You can easily remote your humidistat upstairs..

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