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My basement is about 61 degrees (Fahrenheit). I have a dehumidifier and i think it is working fine in that it is removing water from the air. When I first got it the humidity was about 70 % and the dehumidifier has gotten that to around 55 % - 60 % running constantly. I just learned that dehumidifiers aren't recommended for basements colder than 65 degrees.

  1. Why is that?

  2. What are alternatives to dehumidifiers in a cool basement?

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  • I'd fully expect the temperature to go up with the dehumidifiers running. Presumably the concern is something like icing up the intake coil, but I would not worry about 61 .vs. 65 on that basis, especially since my experience is that it would soon be over 70 (but drier) with them running.
    – Ecnerwal
    Jun 20 '21 at 19:43
  • I have had it running for at least a month. It is still about 61 degrees. But maybe I am just overthinking this.
    – John Doe
    Jun 20 '21 at 19:45
  • Your basement is damped but not humid. We know humidity is directly related to temperature, but dampness is not, it depends on the availability of water that affecting the immediate environment. The dehumidifier is set up to run at a constant rate to condense the moisture in the air through temperature difference, the smaller the difference, the less efficient it runs, thus the negative recommendation. You shall check your basement for the cause of consistent dampness.
    – r13
    Jun 20 '21 at 20:31
  • My basement air is circulated through the house, there is a cold air inlet in the basement as well as upstairs. There are also vents. The basement stays cooler but dry. This mitigates any potential mold problems.
    – Gil
    Jun 20 '21 at 21:24
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The issue with dehumidifiers is they are basically air conditioning units that once they cool the air by passing it over the evaporator coil to collect the moisture they reheat it by passing the air over the condenser coil, the energy consumed slightly warms the area.

The problem is the evaporator (the part cooling) will not be as effective because of the cool ambient temperature and may ice up.

It sounds like your system is working ok but would be more effective/efficient at a warmer temp.

If you’ll notice many home ac units don’t have set points below 62 similar reason because the evaporator is so cold it ices up and doesn't cool as well. So although you are at that threshold it sounds like your system is working, but it may not be at peak efficiency because it is at the lower limit.

If this explanation doesn’t make sense take a glass of ice water put it on a table and time how long before it starts sweating. Wipe the glass dry and put it in the refrigerator and wait the same amount of time and check the glass, less condensation because of the limited temp differential (well the air in the fridge is dryer) but trying this experiment upstairs in a warm room and then in the basement will show the cooler room condenses less moisture even though it may be more humidity (again there are factors that affect this but it may help to visualize).

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    In my shop (hobby woodworking), it's normally about 58-62 F, partially Earth sheltered with high stem walls. I run a dehumidifier to keep it about 60-65% RH, because I have a bunch of exotic hardwoods that I don't want to grow and shrink on my, esp. after I use them in a project. I've never had a problem with it icing up. There is a drain line that runs to the outside driveway. It's a portable unit with a container for condensate, but with the drain line, I don't have to empty it every day. Hope this comment helps. + to Ed. Jun 20 '21 at 23:57
  • @george Anderson yes you are at that threshold although I remember them talking about it in training years ago 62 rings a bell for me they may work reasonably well down to 55 depending on how it is set up but as the temp drops the efficiency is reduced not saying that they won’t work as your experience shows yours is working down to 58 and the 1200w or so is like one of those little electric heaters helping to warm the area not a lot of heat but some.
    – Ed Beal
    Jun 21 '21 at 1:59
  • It does provide some heat. Here in damp western washington state, it probably ran more during the fall/winter/spring. I doesn't get all that cold here so that's probably why I didn't have any freeze up problems. BTW, Ed. One of these years, If I get down to Bend, I'd love to have a cup of coffee or lunch with you, I think we have a lot in common. Jun 21 '21 at 2:59
  • @george Anderson I am in dexter but do head over on occasion sounds like fun.
    – Ed Beal
    Jun 21 '21 at 13:13

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