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  1. #1
    While I'm here, I was wondering if anyone has any information on a type of humidifier that I installed, have been using for several years, and have never seen before.

    I purchased the unit from a low budget hardware store and noticed they no longer sell them. The unit is called ThermoMist and works as follows.

    The unit injects a stream of water into the sytem above the A coil which is above the furnace. It senses the heat from the furnace blower turning on and then begins the water injection using one small water spayer which shoots into the ductwork. It shuts off similarly when it no longer detects the heat from the furnace.

    I bought the thing because it was cheap and easy to install. But after using it for a couple of years, I noticed that if not set just right, it can soak the inside of the furnace with water and cause all sorts of residual filled water to run out the bottom of the furnace. Makes me wonder where all the dust the thing is wetting down is going? It also makes me wonder if the thing is causing any damage to the A coil which is directly under the water jet?

    The thing does work. In winter I can definitely tell the difference in indoor air quality when the unit is not working or shut off. The dust piles up more when the unit is off. So it must be soaking the dust with water and then sending the heavy dust to the A coil to be washed out with the drain, right? Or is the dust just building up in the form of residues in the water and covering the A coil? I haven't seen the A coil in a couple of years, but the water trails when the thing malfunctions are all white with dried residue and dust.

    Should I quit using this cheap and dirty humidifier? If so, are there any better alternatives to adding a humidifier than a drum roller? I can't live in this house without a humidifier in winter. I've tried it, and I don't like it.

    Thanks. I've got a dust problem in this house which can be discovered from my post(s) in the Residential HVAC forum of this website. I probably have water quality issues as well. The water from the city supply when dried, leaves behind a bright white powderery film. I think there are too many chemicals in the water supply, at least in my neighborhood. Don't have a water filter or water softener, but am thinking of getting one. This hard water may add to the damage the humidifier is doing to the furnace/A coil if any from spraying above it.

    Any thoughts? I also want to add a whole house air filter at the furnace. I guess Aprilaire is the best right now or is it Honeywell? Do these things work? Thanks agian.

  2. #2
    Join Date
    Jul 2001
    Central MN and the Twin Cities
    If you do a search on this site you will see there has been alot of talk about those humidifers. The overwelming opinion is that they are junk and ruin furnace and ac coils faster then almost anything we have seen. I would stop using it imediately and hope that it is not too late. The damage may already be done and years of life could be robbed from your furnace. Like with anything metal water causes and speeds up the "aging" process. I wish homeowners would learn this one lesson.... most of the cheap crap you can buy in any hardware store or home center is sold there because the real contractors would not buy it through the regular supply houses and other wholesale channels. Most manufacterurs make different lines or grades of products. The good stuff goes to the pro's and the cheap crap goes to the homeowners. There are many examples of manufacterurs after failing to sell certain items to the pro's turning around and repackaging the items for the "public." After all with proper marketing you can sell anything to the uninformed. I will not waste the time to explain all the reasons why the type of humidifier you have has problems or why they almost always are installed or maintained incorrectly. Let me just say this.... "In my 15 years around the heating buisness I have never seen a furnace with one of those humidifers that did not have damage caused by it and as a result years taken off the life of the furnace." I would advise you to seriously have a true professional furnace person do a complete check before fall for safty reasons. This is not a scare tatic, I am serious. I have seen those humidifiers ruin furnaces in under one year. Yours has been running multiple years and you even state has "soaked" your furnace before. Think about this... your furnace is heating up a metal chamber to warm the air it is moving and the lifespan of that heat exchanger(the chamber) is effected by how evenly it heats up and cools down because of how metal expands and contracts with heat. Now what do you think happens when you heat metal up a few hundred degrees and then dunp cool water on it? You CAN crack a brand new heat exchanger that has no signs of rust you know!? The only humidifiers any company I have ever worked for installs are self-contained units with drains that contain no standing water. Even then most contractors around here install them as much as possible on the return drop side of the plenums to eliminate the possibility of water leaking on a heat exchanger. Please consider this when choosing a new humidifier. Honeywell and April Air are bolth excellent units.
    Warning: Just because I am over the head injury doesn't mean I'm normal!

    The day I stop learning.... I'm dead!

  3. #3
    Try out Nortec:

  4. #4
    Since this post I have done several things. First, I removed a vent that is located directly above the A coil and took a good look inside. The A coil has a coating of white powder on it and you can see where the jets from the Thermo Mist were spraying on the sides of the ductwork.

    The A coil looked good but I used a brush and a shop vac to clean her up anyway.

    Took the advice I found here on this website and found an Aprilaire 600 for about $70.00 brand new. I would have liked the 700 but I could not afford it.

    Have yet to install the humidifier but it looks pretty straight forward. For some reason, they recommend the unit to be mounted on the supply side of one kind of furnace, and the return side of another. I'll simply follow the instructions and mount the thing just like the picture shows for my furnace.

    I also have a new water softener I purchased at about the same time. It was also brand new and I am not going to disclose the purchase price as it might make me look like I stole it. But I got it cheap.

    The water softener I did install right away as it got banged up pretty good in shipping and I wanted to make certain it worked. Took some real creative thinking, too, to get the water supply seperated, the outside lines seperated and the unit inserted in between the house supply. But I am pretty good with a torch and had CU sweat pipes to work with.

    The point is, I noticed a difference right off in the quality of the water. No more white rings in the kitchen sink. In the shower and bath, the water almost seems slimy which is a good thing. I am very happy with the water softener and hope this new source of water, coupled with the new humidifier will improve the quality of my life in winter.

    I also bought a used vacuum cleaner to replace my old one which threw a bearing, then was discovered to be blowing back into the air most of the dust it removed from the carpet. Again, I anticipate a big improvement in quality of life.

    One day I hope to replace the two Honewell room air purifiers I purchased with a whole house model. Don't know which one, but Aprilaire seems to be leading the pack in quaility. But that won't for a while as the $400.00 +/- for the unit is not in my future.

    I am curious as to why the Aprilaire installation brochure shows the unit being mounted on the supply duct in upflow situation and on the return in the downflow situation. The weight of the water or something, I guess.

    Thanks for all input.

  5. #5

    No Problems

    I have been using the ThermoMist humidifier for some 31 years. Absulutley no problems to report. The unit provides the desired level of humidity. There is no maintainence to speak of. I did install an in line water filter. I used a refrigerator type in line filter. If the humidifer is installed and set correctly there is no water spillage. As an extra level of protection you can wire the unit to turn off with the blower. I did not not have to do this but have considered it. Now after all this time, it is safe to conclude, at least in my case it was not necessary.

  6. #6
    Join Date
    Oct 2009
    Murfreesboro, TN
    I once heard it said that if you use an atomizing humidifier you have to have a UV light installed immediatedly downstream to keep the fungi under control.

    Atomizing, adiabatic humidifiers are not really suited for residential use for various reasons. Steam units that empty after not being used for 72 hours and have controls to reduce scaling are the best way to go. The only thing left to do is size the capacity for the entire cubic area of the house allowing for 'loose', 'average' and 'tight' construction requirements.

    The AprilAire 5000 air purifier has been rated as a 'best buy' by CR before. Any gasketed, deep pleated box filter is a step in the right direction.

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