Dehumidifying and Drying Air Information Dehumidifying and Drying Air Information

If you frequently smell musty odors or feel damp spots on the floors or walls of your basement, laundry room, or storage area during warm, humid weather, you need a dehumidifier.

The recommended humidity level inside your home during the summer is around 40 to 50 percent, and very humid conditions over an extended period can leave you uncomfortable and adversely affect your home. Musty smells, peeling wallpaper, warped wood, rusting tools, blistered paint and moisture dripping from pipes are signs of excessive humidity. These conditions are most common during spring and summer.

Dehumidifiers remove excess humidity by drawing moist room air over cold refrigerated coils. The moisture in the air condenses into droplets as it passes over the cold surfaces in the dehumidifier and into a container. "Dried" air then returns to the room at approximately its original temperature. For best results, the unit should be located in an area closed to outdoor air and where air movement in and out of the unit is not restricted.

Here are some features to look for on many of today's models:

  1. Automatic turn-off switch that shuts unit off when container is full
  2. Signal light indicating that container is full
  3. Adjustable "fill" control that stops unit at the desired "fill" level
  4. Automatic humidistat that maintains the desired humidity level
  5. Automatic defrost control which shuts compressor off when freeze-up develops and turns it on again when ice is melted. (This occurs when temperature and relative humidity are low.)
  6. Combination dehumidifier/heater to warm a room that tends to be chilly frequently
  7. Quiet-running compressors and fans
  8. Easy-to-reach controls
  9. Easy-to-clean grille, condenser coil and container
  10. Rustproof, spill-proof container with built-in handles for portability
  11. Drain-hose fitting to let water run continuously to a convenient drain
  12. Wheels or rollers for easy mobility
  13. Rust-resistant cabinet.

While control or built-in features may increase a model's convenience of operation, they also raise its price. Consider each option carefully before you decide it is worth purchasing. But the most important consideration is "water removal capacity," the number of pints of water removed from the air in 24 hours.

Energy efficiency is important in dehumidifiers. Differences of only 85 watts may add 20 kWh daily to your summer electric bill. Some models let the fan run continuously to circulate air back to the humidistat. Since in most situations the moisture content will be the same throughout the enclosed area being treated, this may be an unnecessary energy expense.

Place the dehumidifier at least 6 inches from the nearest wall where air can flow freely to and from all sides. Avoid locating it in a room corner or near a large piece of furniture. Shut all doors and windows to the area to be dehumidified.

For the first few days of operation, turn the humidistat, if the model has one, to drier or "extra dry." This aids moisture removal from furnishings as well as room air. After the area has dried, adjust the humidistat to your particular comfort level.

Before you empty the water pan or bucket, turn the machine off and also disconnect the power cord. This eliminates any possibility of electric shock if you spill water and there is a fault in the grounding
system of the unit or your home wiring. Be sure the area, the unit, and you are dry before you reconnect the cord.

Dehumidifiers operate most effectively at air temperatures about 70 F. At temperatures below 65 F frost may form on the coils (which are kept cold to condense as much moisture as possible). If this happens, shut it off, and wait for it to defrost before running again. Frost cuts down air circulation so the dehumidifying process does not work, and may damage the coils. This problem usually occurs in cool basements in spring or fall; check the appliance if temperature hovers near that point.

As water condenses out of the air, heat is given off, raising the temperature slightly in the area around the appliance. This warmer air results in a lower relative humidity.

Cleaning

Dehumidifiers need little upkeep or care. The following simple procedures are sufficient:

Always unplug the power cord before cleaning the unit. For regular cleaning, dust the grilles or louvers with a soft brush or the dusting attachment of a vacuum cleaner. Either dust the cabinet or wipe it with a damp cloth. Every few weeks, scrub the inside of the water container with a sponge or soft cloth and a mild detergent to discourage the growth of mold, mildew, or bacteria. At least once each season, remove all dust and lint from the cold coils with a soft brush.

Always plug a dehumidifier into a three hole grounded outlet. If there is none where you want to put the unit, make sure you install one properly. Using extension cords is not advised because if an extension rests on a damp floor or if water spills on it, is a shock hazard. If you must use an extension cord, be sure it has a three-hole receptacle and three-prong plug for grounding. If a three-hole, grounded outlet is not available, convert it following our instructions and grounding properly. This is particularly important for a dehumidifier because it may be operated on a damp floor that could conduct electricity and because it collects water, which could spill and cause an electrical accident. Never remove the third prong from a dehumidifier plug; to do so invites an electrical accident.

A dehumidifier's fan motor should either be permanently oiled or easy to reach for oiling; the refrigeration system motor is sealed and never needs oiling.

This article has been contributed in part by Michigan State University Extension

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