I have a Trion cm200 installed on my air handler up in the attic of my house. Toward the end of 2018 I had an entire electric system installed in my house (duct work, air handler and outside condenser ) . Did away with the old oil burning radiator system. I decided to have them install a humidifier while they were at it. Keep in mind all this was done while house was under construction. I was not living there at the time.

The first time I used the humidifier, i set it to roughly 40% because the humidistat has a guide on the front that says what percentage to set the humidity in comparison to the outdoor temperature. At the time was roughly 10-20° outside for a couple weeks. The next day my hallway ceiling was leaking. The humidifier ran so much that the air handler actually took water in and was just dripping non stop. I shut it off. cleaned it up then a couple weeks later I tried it again. Same thing happened. I did not call the installers back because they were friends of mine and (“ I got what I paid for”). Also I don’t think the installer was that familiar with installing a humidifier. However they did a great job with the rest of the system. I shut the humidifier off for the rest of the season.

Summer passed. AC worked great. This winter 2019-2020 is here and we been running the heat with no humidifier because I was nervous. About 3 weeks ago I decided to give it a try. I turned it up slightly to 10% on the humidistat And the humidity in the house changed slightly from 25% to low 30% after a few days. So after that I cranked it up to about 15% on the humidistat and let it go from there. I would gradually check my Nest thermostats. (I have 2 zones. 1 on first floor other on second floor). The house was hovering anywhere from 37%-42%. So I figured it was working properly. I noticed I been waking up the past few days with a very dry nose. The thermostats are reading 25% again...

So here I am no seeking help. It seems like I read elsewhere that the return vent is a good location for the humidistat. Mine is on the return but it’s after the humidifier in the flow of air. So it’s like this. (Return air —> humidifier —> humidistat—> air handler—> vents) I’m wondering if the humidistat is getting false readings because it may be after the humidifier but I don’t know if that’s why. Just a thought. Also another question is. Can I bypass the humidistat and run the humidifier off my nest? I do have spare wire running to the thermostat. I will attach a photo bellow. The arrows indicate air flow

Thank you in advanced for infoenter image description here

  • "The humidifier ran so much that the air handler actually took water in and was just dripping non stop." - forget about where the sensor is (which doesn't really matter, I read once that humidity disperses at 25' per second... it is where it should be anyway - on the return chamber), that's your problem. It should be able to run 24/7 and that not happen. Reduce the flow on the bypass.
    – Mazura
    Jan 10, 2020 at 1:25
  • So I should adjust close the damper to let less air flow through the bypass vent? Jan 10, 2020 at 11:49
  • It has a damper; that's an easy fix. That bypass duct isn't where it should be. It's directly on the unit instead of further down on the plenum chamber, so it gets blasted.
    – Mazura
    Jan 10, 2020 at 14:42
  • Double check the connections in the humidistat control. If there are 3 terminals, the control may have both normally open and normally closed contacts. This would enable the control to work either as a humidistat or as a dehumidistat.
    – John Canon
    Jan 12, 2020 at 2:47
  • Did they put a pressure switch on? If the unit has its own power it may be running after the furnace shuts off. The pressure switch will turn it of when it senses no air flow. Also, you may want to adjust the amount of water going through the system by closing the valve some. Mar 4, 2020 at 21:42

1 Answer 1


Two points. First, be sure you are using a humidistat and not a dehumidistat. With a humidifier you need a control (humidistat) that shuts off the unit when the humidity gets too high. When you have a dehumidifier or HRV you need a control (dehumidistat) that shuts off the unit when the humidity gets too low. From your description your control just keeps the humidifier going and going, like a dehumidistat telling the humidifier to keep running. Second, the humidistat should be in a location that reflects the actual humidity of the dwelling space. An open wall near the return vent would work.

  • 1
    The humidistat came with the humidifier. So I would hope I have the correct one. But I guess things can always be packaged incorrectly Jan 10, 2020 at 11:40
  • On my furnace, the humidstat is upstream of the humidifier in the return plenum. It should sense the air before treatment. Maybe if you were to move it to left of your active unit (given the photo showing left to right flow)
    – DaveM
    Apr 4, 2020 at 1:17
  • Ditto that...the air is humidified as it leaves the furnace, the sensor is in the return plenum where the air returns to the furnace. Apr 4, 2020 at 14:46

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