DEHUMIDIFIERS

Refrigerant Dehumidifiers

Refrigerant dehumidifiers work by creating a cold coil (Evaporator Coil). This coil needs to be maintained at a temperature colder than the surrounding air (Dew point), in order for the moisture held within the air, to condense. A fan within the dehumidifier draws the air over the cold coil, where any moisture condenses into water and drains into the collection tray / bucket.

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The Air then passes over the warm coil (Condenser Coil) where it is reheated. This warm “dry” is the exhausted from the dehumidifier back into the space being dried. When used in colder climates (generally below 18°C), frost/ ice will start to form on the cold coil. Periodically the dehumidifier will go through a defrosting cycle, either by energising a valve within the unit (Hot Gas Bypass method), or turning the compressor off (Passive defrost method). During the defrosting periods the units dehumidifying capacity is reduced.

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Since refrigerant dehumidifiers rely on a temperature difference, between the cold coil temperature and room air temperature, they generally work better in warmer environments, also operating in temperatures above 18°C will eliminate the need to defrost, and consequently further improve the dehumidifiers performance.

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Benefits of a Refrigerant Dehumidifiers:

• Compact standalone units with minimal connections (Power and Drain, some units have internal containers which would require emptying)
• Ideal for temperatures between 16°C and 35°C
• Energy efficient

Desiccant Dehumidifiers

Desiccant, sometimes referred to as adsorption dehumidifiers, have a different method of operation. A honey comb wheel which is impregnated with Silica gel rotates very slowly with the dehumidifier. A fan draws air (Process Air) over three quarters of the wheel, and any moisture in the air “sticks” to the honey comb matrix, drying the air before being exhausted back into the space being dried.

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As the wheel rotates, it passes through a quadrant where a second air steam (Regeneration Air) heats the honey comb matrix to a high temperature, which in turn releases the moisture removed back into the regeneration air stream. This hot humid air must be exhausted outside the space being dried as it contains the moisture removed.

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Unlike refrigerant dehumidifiers, desiccant dehumidifiers operate efficiently across a wide range of temperatures, and since they produce hot humid air rather than water, will operate in sub‐zero climates. Since the Honey comb wheel retains a portion of the heat added during the regeneration phase, the air being dried leaves the dehumidifier not only dryer, but also warmer.

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Benefits of a Desiccant Dehumidifiers:

• Works well across a wider range of temperatures
• Simplistic operation
• Generally, quieter

Disadvantages

• Additional ducting / installation required
• Consume more energy, therefore more expensive to run