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DennisDe Member Posts: 16
Question for the expert..I have installed the xr9 trane with macthing coil and condensing unit for my 1800 sq ft basement. I have also included a media filter-aprilair 2200. My question is do I have to let my A/C run at 74 degrees throughout the summer in order to prevent moisture / mildew problems. Is there another option to letting the A/C run..will the installation of a dehumidifier help. It just seems like if the A/C has to stay running even when I am not in the basement at the time could be costly...correct?


  • JimGPE_8
    JimGPE_8 Member Posts: 15

    It is quite possible that running a dehumidifier is the ONLY thing that will work if there is no heat gain in the space (lights, windows, equipment, etc.).

    A dehumidifier is a cooling coil that cools and dehumidifies the air, then takes the heat it absorbed and puts it back into the room air and sends the moisture to the drain.

    An air conditioner does the same thing but rejects the heat outdoors instead of into the room.

    The net result of dehumidifier operation is less moisture in the air, and a slightly warmer room.

    If there is no cooling load in the room and you force your air conditioner to run by turning down the thermostat, you will over-cool the space, making it uncomfortable, AND your relative humidity will go UP, not down.

    The only way to use an air conditioner to dehumidify the a space that has no call for cooling is to cool the space then heat it back up again.

    Confusing, I know, but the sum is to tell you to spend $150 on a dehumidifier. The op cost will be less, and it will actually work.
  • DennisDe
    DennisDe Member Posts: 16

    Jim what would be your brand recommendation for the 150.00 price range you suggested..1800 square ft basement
  • JimGPE_8
    JimGPE_8 Member Posts: 15

    I have one that is the KMart house brand - Gold something. Its lasted 15 years. Don't really know what they go for now, but they're still not expensive.
  • Matt Clina
    Matt Clina Member Posts: 90
    Sears Dehumidifier

    I have about a 5 year old version of this one:


    I bought it as a floor model, and got about 50 bucks off. My basement is much smaller than yours (about 800 sf), and I have to dump it about once per day. If you can rig it up to a drain, I would highly recommend it. Then you could forget it is there.

    The bucket on mine has a knock out for a hose fitting, but my drains are too high for gravity draining, so I use it to water my plants every evening.
  • DaveGateway
    DaveGateway Member Posts: 568
    if you don't like the heat

    the dehumidifier puts out and have a small window, pick up a very small cheap 5K BTU air conditioner. It will probably run constantly and burn out in a couple of years but you can get them for under $100 bucks. At least it will dump water and heat outside and only use use a few hunderd watts instead of running the whole central unit. I got an undersized ductless minisplit in my basement rather then have the house central air overcool the space.
  • Dale
    Dale Member Posts: 1,317
    AC size

    The question is whether your AC is sized small enough to run long enough to dehumidify. Also, is you fan speed set low enough to dehumidify. I you live up north the AC setting from the factory is for Tennessee or someplace that need 3 tons of AC for a 1500 sq ft house. I always set the fan speed down at least one speed and the delta tee isn't too high. I would try the AC by it self and if you leave the windows closed during hot weather it may work OK.
  • Bud_14
    Bud_14 Member Posts: 200

    This morning I sat in with a few guys and got the low down on humidity. I thought I was smart but this little discussion made me realize I should become smarter on the subject of humidity, seeing it is what we try to control most of the year for maximum comfort.

    I would seriously try to educate your self on the difference between the portable units and a whole house unit. The whole house unit can operate at times when you need to remove the humidity, but don’t necessarily need the AC running?

    Also understand that when they say x amount of pints per day, usually means at 80 deg F.... your basement is not 80 deg. F. Basements here (I believe everywhere) are about 55 deg. That x amount of pints per day is not accurate? Is the dehumidifier now less efficient? Or is the capacity less when the ambient temp. is cooler?

    Dose anyone know what happens to the "pints per day" figure when you place the dehumidifier in the basement?

    Another thing to keep in mind is that the humidity in the home is the same, everywhere, what you feel in the basement is "Relative Humidity". The temperature and the humidity level determine the R.H. The cooler it gets the more R.H you will have.

    You see, there are lots of things to think about and the comfort level you wish to achieve.

    I would contact a professional in your area that can give you the Humidity 101 and set you up to be comfortable.

    I’m not trying to give anyone a free plug here but the April Aire Model 1700 Whole-House Dehumidifier is worth looking into and will give you an idea of what the difference is between the two.

    Many people don’t know there are choices.


    Honeywell may have a similar product?


  • JOEL_11
    JOEL_11 Member Posts: 1

    I wouldn't buy any of those cheapy units 8 of 10 are junk . The poster who said look what happens to the output in a cold basement was spot on. We sell the ones from Thermastor like the Sahara model. These really work we put one in abasement that had 3 cheapy models and was still very wet. That thing dried it out in a week. They have models you can duct as well. Not cheap 1500+ depending on the set up but at least it works well and is very well biult those 299$ things are biult to be the cheapest in the sunday sale fliers.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    Is a good (if technical) publication on sizing for dehumidification.

    In a basement you want to be able to keep the humdity below 65% as the growth of mold will be impossible or at least severely slowed. 60% is probably a good target when sizing.

    That can involve a LOT of water removal in conditions like around here. Right now I show 92.3° outside with 55% humidity. Basement is 73.2° and humdity 69%. (I'm glad you posted this as it made me check my basement humidity--it's not supposed to be that high so I checked the dehumidifier--the outlet hose was clogged and the unit had shut down because of the full tank.)

    Dehumidifiers seem to be rated in nearly impossible conditions (80°-90° with RH of 90° or so). I'd associate those conditions with my hay hauling days as a kid when you've loaded a barn nearly to the ceiling with fresh-cut alfalfa hay. I can't seem to find a single unit rated at more realistic conditions. The "rule of thumb" that seems to keep popping up is to calculate the actual moisture you need to remove and select a dehumidifier with double that capacity (given their wacko rating system).

    Psychometrics often work "with you" during the winter in a basement as the basement is typically warmer than the outside air and your need to dehumidify is greatly reduced or eliminated. Dehumidifiers still work in low temperatures--the problem is that ice will form on the condensing coils and capacity becomes GREATLY reduced. Most of the "low temperature" units use some form of hot gas bypass into the condensing coils. Some will do this continually, others wait until pressure "tells it" that significant ice has formed and will do a full hot gas diversion to rapidly de-ice. The second method is supposedly more efficient and less "hard" on the compressor, but it comes at a higher price.
  • Uni R
    Uni R Member Posts: 663
    Dehumidifier and plants

    If you could seal the soil with plastic wrap that water wouldn't get back to the dehumidifier so quickly. Nice loop you have with that. L
  • Matt Undy
    Matt Undy Member Posts: 256

    You could always put a condensate pump in the drian pan or hang the dehumidifier to the ceiling. The plants give off a lot of that water you put in them through their leaves too.

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