Question about Aprilaire 400 Humidifier

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Aprilaire 400 - Mesh Screen not wet

The mesh screen is not consistantly's only wet in places... There's enough water running through the system, the water just doesn't drip down in a uniform fashion that makes the entire screen wet. Any suggestions? This did happen after I took it apart and cleaned it and replaced the filter. I put it back exactly as it was, but now the water doesn't seem to drip down evenly enough on the mesh screen. Any ideas?

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  • pmarkovina Dec 21, 2008

    Same problem here, and it's very frustrating. The entire bottom of the mesh screen is wet, and the two float reservoirs are filled, which turns off the water valve; the furnace keeps running, blowing air through the dry mesh, providing absolutely NO humidification. Since the floats are floating in water, the unit will not turn on. Poor design. Can someone help? -Pal

  • tossit Sam Feb 04, 2009

    The left float is an overflow safety shutoff as far as I can tell. I mopped that side dry and the humidifier came on once the right float dropped(water soaked up), These seem to have a design flaw as my filter is never wet but the bottom two or three inches. Even hooked to hot water it takes a long time to push any moisture into house air. Then it shuts off at what the control says is 45% but a hygrometer I have upstairs says it's only 29% up there in the living area. Then the control reads 40% when it has come back on so it doesn't/can't hold the moisture anywhere close to its maximum. Not happy with this machine.

  • Robert Pladek
    Robert Pladek Dec 11, 2016

    me too; just had this put into my home this last week. I also saw the pad only wet on the bottom 1/3. The humidity never gets up to expected level. Seems like a bad design or pads are not designed as wicks to pull water up to top....



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Not happy either. I bought 3 Aprilaire 400 for my house (3 zones). I picked this style since I have attic installation and did not want to run drains. The first night I expected a major air quality improvement but no change in humidity. I have installed humidifiers before so I know the drastic improvement they make. So I watched for a season and still no humidity improvement. Absolutely nothing at all. Same exact observation as you all described. Only the bottom of the media was wet. I'm dissatisfied with Aprilaire 400. Do not buy! Since I installed humidifiers before and understand them I am converting the Aprilaire 400 to work like a Aprilaire 600. I simply unwired the float sensors, removed the floats/lid and using a knife cut some of the plastic cups so the water would drain well. I also cut open the plastic exit port some too so it wont clog from dust globs. I obviously added drains. HUGE RESULTS. On the very first cycle on the humidity in that zone went from 25 to 48. I am watching carefully. -GK

Posted on Jan 09, 2011

  • Robert Pladek
    Robert Pladek Dec 11, 2016

    Please help me with a clarification on your idea... Is the 600 equivalent that you've rigged a non-drain solution? or drain solution?

    I bought the 400M originally to avoid frozen water in an attic install. (I also ran heat wire along the entire system to avoid frozen water line.)



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