(NOTE: After reading this article, you may want to take a test on its content. To do so, follow this link: Dehumidifier Test)

Locating the Dehumidifier

A dehumidifier operating in a basement will have little effect in drying an adjacent enclosed area, such as a closet, unless there is adequate circulation of air in and out of the adjacent area. Remove interior doors and operate dryers to maintain good air movement.

Under normal circumstances the dehumidifier should be positioned centrally in the room. If, however, a particularly wet area is apparent, the air outlet grill can be directed towards that part of the room.

Normally, the dehumidifier will be serving an internal room volume between 1,000 and 5,000 cubic feet. In smaller rooms, it will raise the internal temperature substantially. This helps reduce the relative humidity (RH) and, therefore, assists in the drying process.

Operating Conditions

A light coating of frost on the coil is normal when dehumidifier begins to operate, due to the freon rushing through the coil. Under normal conditions, it should disappear within 60 minutes. It is also perfectly normal for frost to form on the coil when the temperature of the room is relatively cool and/or if the humidity in the room is relatively low.

When the dehumidifier is first put into operation in a saturated environment, it will remove relatively large amounts of moisture. It will continue to do so until the relative humidity in the area being dried is reduced to a point where moisture damage will not occur. After this, the amount of moisture removed from the air will be considerably less.

The reduction in the amount of moisture being removed indicates that the dehumidifier is doing its job and that it is maintaining the relative humidity at its best level. The performance of the dehumidifier should be judged by the reduction of relative humidity, rather than by the amount of water being removed and deposited in the bucket.

Extraction Rates

In all dehumidification systems the extraction rates vary with humidity and temperature. An electronic hygrometer will help in checking for proper operation. The following chart provides some examples of extraction rates at various conditions:


60 F - - 60% - - 12 Pints
60 F - - 70% - - 20 Pints
70 F - - 60% - - 30 Pints
70 F - - 70% - - 40 Pints
80 F - - 60% - - 50 Pints
80 F - - 70% - - 57 Pints
80 F - - 80% - - 67 Pints
90 F - - 80% - - 73 Pints
100 F- - 80% - - 75 Pints

Electrical Supply Connections

This dehumidifier is provided with a heavy-duty electrical cord. The unit may be operated from a 110v system only. Extension cords must be heavy enough to deliver at least 8 amps. It is extremely important that the voltage at the unit itself is within a tolerance of 10% of the nominal rating. As the length of cable increases, the voltage available at the unit decreases. The following table provides a guide to maximum electric extension cord lengths:

16 AGW for up to 15 ft.
14 AGW for up to 30 ft.
12 AGW for up to 60 ft.

If there is any doubt about available voltage, then the voltage should be tested at the unit on compressor start-up. If there is a "dip" of more than 10% from the nominal supply rating, then action should be taken to improve the supply. Under no circumstances should the unit be left operating.

For Proper Operation

  1. During transport secure the unit to keep it upright.
  2. If unit has fallen over, set upright for an hour before operating.
  3. To prevent flooding, operate the dehumidifier only on a level surface.
  4. Plug the unit into a grounded 110v outlet and switch "on" to start.
  5. If unit shuts off for any reason, allow 5 minutes before restarting.
  6. Listen for proper operation of the fan and compressor before leaving.
  7. Locate the drain hose into a suitable six-gallon container or drain.