Dehumidifier Control

As mentioned previously, the dehumidifier (see Fig. 3-19) operates on the principles of the conventional household refrigerator. It contains a motor-operated compressor, a condenser, and a receiver. In a dehumidifier, the cooling coil takes the place of the evaporator, or chilling unit in a refrigerator. The refrigerant is circulated through the dehumidifier in the same manner as in a refrigerator. The refrigerant flow is controlled by a capillary tube. The moisture-laden air is drawn over the refrigerated coil by means of a motor-operated fan or blower.

The dehumidifier operates by means of a humidistat (see Fig. 3-20), which starts and stops the unit to maintain a selected humidity level. In a typical dehumidifier, the control settings range from dry to extra dry to continuous to off. For best operation, the humidistat control knob is normally set at extra dry for initial operation over a period of 3 to 4 weeks. After this period, careful consideration should be given to the dampness in the area being dried. If sweating on cold surfaces has discontinued and the damp odors are gone, the humidistat control should be reset to dry. At this setting, more economical operation is obtained, but the relative humidity probably will be higher than at the extra dry setting.

After 3 or 4 weeks of operation at the dry setting, if the moisture condition in the area being dried is still satisfactory, the operation of the dehumidifier should be continued with the control set at this position. However, if at the setting the dampness condition is not completely corrected, the control should be returned to the extra dry setting. Minor adjustments will usually be required from time to time. Remember that the control must be set near extra dry to correct the dampness conditions but as close to dry as possible to obtain the most economical operation.

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