ICS Magazine

Differing Dehus

December 8, 2005
Where moisture is concerned, dehumidifiers and air movers are near the center of the restoration universe. In the simplest terms, air movers lift moisture from wet materials and evaporate it into the air. Dehumidifiers then separate the moisture from the air and remove it from the environment. There are three basic types of dehumidifiers: commercial-grade refrigerant, low-grain refrigerant and dessicant.

Commercial-grade refrigerant, or CGR, dehumidifiers are calibrated and designed for high-moisture environments, using advanced defrost controls to maximize performance. The coil and compressors are larger than those in residential units. CGRs come in two varieties, standard and conventional, the difference being that a conventional unit use a heat pipe or defrost cycle to defer frost from forming on the coils.

Electric refrigerant dehumidification consists of air passing over refrigerated coils to condense water vapor. At cooler temperatures, though, refrigerant dehumidification capacity may fall off before reaching ideal moisture levels. That opens the door for...

Low-grain refrigerant, or LGR, dehumidifiers, which use a double-cooling step to lower the moisture-laden air temperature once it is inside the unit so more condensation can form on the internal cooling coils. LGRs are more energy efficient than CGRs and can pull the grains down much lower. As the condensation builds up on the coils, the water droplets drip into a collector and are discharged. LGRs produce air that is dryer, heated and that contains less moisture than CGRs.

Instead of the process of condensation, dessicant dehumidifiers use a silica gel wheel or rotor to remove moisture from the air. A dessicant is a material that attracts and holds moisture. As wet air passes through the rotor, the moisture is absorbed by the silica gel. When the wheel rotates through heated exhaust air, the moisture evaporates and is then carried outside of the structure. Dessicants can reduce relative humidity far below refrigerant dehus, and can be used for drying materials like wood floors. Dessicants do not depend on air temperature to dehumidify, and can operate easily in below-freezing temperatures, but they are not as effective when humidity is high.

Air movers come in a variety of shapes, sizes and applications, too many to list here. When they first arrived on the restoration scene some 30-plus years ago, they made an instant impact on the industry. Some are designed to create laminar airflow and increase evaporation for water-damage restoration. Others are geared toward ventilation, while others balance pressure and volume for specialty drying applications. This is not just some simple fan: housings are scientifically designed to enhance drying times, focusing and controlling airflow for the best results; airflow angles can be modified for specific drying applications; many units are stackable; and numerous other features differentiate the wide variety of models from one another. The next time you find yourself at a trade show, convention, or even at your local distributor, take a moment to compare and contrast the various air movers on the market today.