As we move into the spring months, your choice of dehumidification equipment changes. While you had needed additional heat in winter, your project may soon need cooling. The performance of the dehumidifier is also greatly impacted by the changing dry bulb and dew point temperature. Where desiccant dehumidifiers were used, we now might consider refrigeration type dehumidifiers.
These units are much like the air conditioner at your house. The coil on your air conditioner has a condensate line that is constantly dripping while the unit runs. This is the water that the air conditioner is removing from the air. Industrial refrigeration type dehumidifiers work on the same principle .
By lowering the air temperature (dry bulb temperature) to a point that is lower than the dew point temperature, they "squeeze" the water out of the air passing over the coil. The water, with no place to go, condenses on the coils, runs down to the drip pan and out the condensate line.
The air leaving the unit is colder, but also drier than what entered. By drier, we mean a lower dew point temperature. The relative humidity is near 100% leaving a refrigeration dehumidifier.
This is why in some applications; we actually re-heat the air to lower the relative humidity. It may sound a little ridiculous, but this is how a refrigeration dehumidifier works. You cool the air past the dew point temperature then warm it up again to lower the RH. This is an effective and very valid method, in warm, wet climates.
When temperatures cool, however, these units become less effective. If the coils reach temperatures below freezing point, they begin to ice up, restricting air flow. Eventually, they must be defrosted.
There have been various advances in this technology to minimize this phenomenon, but there is little that can be done to consistently deliver dew point temperatures much lower than 4 degrees C with refrigeration equipment.
Consider a tank coating project where you are trying to preserve the blasted steel. It is commonly agreed that to do this, you need to maintain the dew point temperature at a level at least 8.5 degrees C below the steel surface temperature.
If the best your refrigeration type dehumidifier can do is to deliver air at a 4.5 degree C dew point, with limited infiltration, you might be able to maintain a 7 degree dew point in the tank. This would mean that your surface temperature had better remain above 15.5 degrees C at night (8.5 plus 7).
So in the real world, we believe refrigeration should only be used when surface temperatures are expected to remain above 18.5 degrees C to ensure the 3 degree C margin can be maintained. Break this rule and you are at serious risk of the blast turning.
Using a material like silica gel, (similar to the pouch of desiccant that comes in a new pair of Nikes or camera case) the desiccant dehumidifier causes the moisture to be attracted [adsorbed) to a large silica gel impregnated wheel or rotor in the air stream.
This wheel slowly rotates through another chamber where a heated airstream heats up the desiccant causing it to release the moisture back into the atmosphere. The continuous process allows the air stream going into the tank or space to be constantly exposed to the dry desiccant, resulting in a very effective removal of moisture.
In order for the desiccant to begin attracting moisture after it was heated, the material must first cool down. This is why these units work much better in cooler climates or if the air is pre-cooled. There is also significant heat generated in the adsorbing process.
The supplemental heat can add to already uncomfortable working conditions in summer or provide more comfortable conditions in winter. Desiccant dehumidifiers will effectively remove large quantities of moisture at all temperatures, but performance is enhanced in lower dry bulb temperatures.
As temperatures cool in the autumn months, consider using desiccant dehumidifiers and putting the refrigeration equipment up for the winter. If you are preserving blasted steel, watch your surface temperatures and don't use refrigeration type equipment when surface temperatures drop below 18.5 degrees C.
VENDOR SAMPLE :: Aprilaire Model 1850/1850W Dehumidifier
The Aprilaire Model 1850 / 1850W Dehumidifier is designed for whole-home dehumidification, basement dehumidification, and dehumidifying crawl spaces and sealed attics. The Model 1850/1850W: Removes up to 95 pints (11 7/8 gallons) of moisture per day! If your home isn't fitted with a dehumidifier, and you are experiencing moistue, condensation or mold problems - an Aprilaire dehumidifier is the solution.
Perfect for your basement or crawl space, the QUEST Dual 155 will remove approximately 155 pt. (80°F/60%RH) in a typical room. Using minimal energy, at only 8.0 amps, the Dual 155 is nearly 50% more energy efficient than many Energy Star-rated dehumidifiers (the QUEST 155 Dual performs at 7.3 pt. per kWh). By consuming less energy, the QUEST Dual 155 creates about 22% fewer BTUs than most alternatives.
Second only to the QUEST Dual 105, the Dual 155 is one of the most energy efficient dehumidifiers out there. In addition to the estimated annual electrical savings exceeding $1,200 a year, the QUEST Dual 155 includes a five-year warranty and is made in the United States.
When it comes to energy efficiency, the QUEST Dual 105 is tough to beat. At only 4.9 amps, the QUEST Dual 105 uses less than half the energy of many Energy-Star rated dehumidifiers (the QUEST 105 Dual performs at more than 8.8 pt. per kWh). Perfect for indoor growing, the Dual 105 will remove approximately 105 pt. (80°F/60%RH) in a typical growroom. The QUEST Dual 105 was designed to be installed overhead, can be placed on a small shelf, or even set on the floor for immediate plug-and-play performance.
If additional space is required, an optional duct kit is available, allowing the unit to be installed outside of the growroom. In addition to the estimated annual electrical savings exceeding $1,200 a year, the QUEST Dual 105 includes a five-year warranty and is made in the United States.
The Santa Fe range of dehumidifiers have been designed to suit a range of different applications.
The Santa Fe Compact2 Dehumidifier is intended for use in tight spaces. Its compact size fits into low-crawl spaces and small basements, without sacrificing power and performance. According to the company, the Compact2 removes up to 33 liters of water per day and provides multiple installation options for greater flexibility.
The larger Advance2 Dehumidifier removes up to 42 liters of water per day, and features a horizontal configuration. It has more water removing capability, but still retains a size small enough to be used to in tight spaces.
The most powerful of the range, the Max Dry Dual XT Dehumidifier has a horizontal configuration and dual outlet design. It removes up to 73 liters of water per day and it is the largest capacity unit in the Santa Fe family.
It has an insulated cabinet, which aims to create quieter operation and enable performance in all larger basement and crawlspace applications.
The UL-listed Utopian Systems Portable Dehumidifier is perfect for removing excess humidity from indoor spaces, and now it's available in a larger capacity. The new 6-pt. per day model is ideal for areas up to 4,000 sq. ft. and allows users to set the desired humidity level between 35% and 85% relative humidity in 5% increments.
When the water tank reaches capacity, the unit automatically shuts off until the tank is emptied. For convenience, the unit has the option to attach a hose for continuous drainage. A removable, washable filter helps ensure good output air quality. The portable dehumidifier also features auto-restart after a power interruption, a 24-hour programmable timer, two fan speeds and a one-year warranty.