It is well published that a refrigeration based dehumidification system works best under high ambient temperature conditions (65 to 95°F, 18 to 35°C; 50 to 80% RH). What is not understood is that these dehumidifiers can be reconfigured to remove moisture at low temperature applications (32 to 70°F, 0 to 21°C) as well.
In a refrigerant based dehumidifier, the evaporator
The ND Series dehumidifiers can be installed either indoors or outdoors. Units intended for outdoor installation are factory equipped with additional insulation, heavy duty weather sealing and special rain hoods mounted on the ventilation air intake. They can also be installed on roof curbs (supplied by others) which permit bottom return and supply air to meet HVAC design specifications when required.
DESERT AIRE’s commercial dehumidifier systems are flexible in their design options. This modular concept allows each system to be customized for specific dehumidification applications:
coil is cooled to below the dewpoint of the air, thereby condensing moisture on the coil. A typical dehumidifier for high ambient design utilizes a hot gas bypass feature to insure the evaporator coil temperature never drops below 32°F (0°C), since below this point the condensing liquid will immediately freeze on the evaporator and eventually cause a system failure. In general, hot gas bypass is activated anytime the entering air drops below a 55°F (13°C) wet bulb temperature (e.g.: 60°F/60% RH) because at this condition the coil leaving air temperature will go below 32°F. In practical terms, as the load drops, the hot gas bypass feature increasingly reduces the performance capacity of the dehumidifier to the point where no moisture will be removed even though the compressor is running. At these conditions, a strain is put on the compressor because large amounts of hot gas refrigerant are short cycled back to the compressor suction .
Amounts of ice build-up are a function of air temperature and it's corresponding relative humidity. Low temperatures when coupled with high humidity will frost up the evaporator quickly. The LT Series dehumidifiers combine numerous design features into a cost competitive system that removes the unwanted moisture problem in low load situations
The LT Series industrial dehumidifiers combine numerous design features into a cost competitive system that removes the unwanted moisture problem in low load situations. Desert Aire starts with an evaporator coil designed specifically for low ambient moisture removal and then adds appropriate refrigerant components to insure long operating life. Each LT System is equipped with an adjustable timer which will initiate the defrost cycle ( if it is needed). The need to defrost is determined by monitoring the suction line temperature and activating the defrost when it drops below 30°F (-1°C). During the defrost cycle, the blower is disengaged and 100% of the system’s heating capacity is diverted to the evaporator where it quickly thaws the coil. The defrost cycle is monitored and automatically terminates when suction line temperatures confirm that the evaporator has fully thawed. There is an additional safety timer which limits the total defrost time to 10 minutes. LT dehumidifiers generate increased air volumes to assist in a “blanketing effect” that provides the required air turns for the facility’s design.
There are two control choices:
The basic design rejects all of the heat recovered during the dehumidification process back to the space.
The space must have the ability to handle this heat gain.
In ice rink applications, the ice refrigerant system is normally able to accept the small additional load. In this control type, a humidistat is installed in the facility and utilized for control of the unit’s compressor operation. As relative humidity increases past the setpoint, the dehumidifier’s compressor is energized to remove unwanted moisture. Blowers run continuously (with the exception of the short defrost cycle) to eliminate false loads created by air stagnation. If the facility cannot, at times, accept the recovered heat, then an optional remote condenser must be installed outside to provide the full cooling capacity. In this mode, a thermostat is also installed in the facility. If the air temperature should exceed the desired set point, the controller will shift the dehumidifier from the reheat mode and reject all of the energy to the remote condenser, thereby providing sensible cooling to the space.
Powders coagulate, papers curl and swell, metals rust, chilled process lines sweat, and product quality deteriorates as moisture migrates through walls and ceilings into buildings, factories, packaging and stamp rooms. Desert Aire provides specially designed industrial and general purpose dehumidifiers for around-the-clock operation, minimal maintenance and high energy efficiency.
Steve Lewis LLC dba
The ND Series is a dual refrigerant circuit, packaged dehumidification system that is carefully designed and manufactured for industrial and general purpose dehumidification.
INDOOR DAMPER/FILTER ASSEMBLY...This ND option can be added to provide integral control of ventilation air. During unoccupied times the damper is closed. During normal natatorium usage the damper is opened to the minimum code position. During high spectator times, the damper is further opened to a higher ventilation rate. The exhaust system is provided and installed by others and must also have a multi-speed motor to match minimum and maximum ventilation capacities. DESERT AIRE’s modulating evaporator damper automatically readjusts air flow across the evaporator coils to maintain proper design velocity.
OUTDOOR DAMPER/FILTER ASSEMBLY... In outdoor installations a rain hood and bird screen are included, but the operation remains the same as the indoor assembly as described above.
Desert Aire’s ExpertAire™ Series dehumidifiers have been designed with this standard in mind. First, we’ve used the latest coil design technology to increase evaporator and condenser capacity while simultaneously reducing their pressure drop. This combination yields the highest MRE available.
Desert Aire’s ExpertAire™ Series products are designed for applications with air temperatures between 65° and 95°F (18° and 35°C) that require moisture removal between 4 and 100 lbs (2 and 45 kg) per hour.
An ExpertAire™ dehumidifier optimizes moisture removal by using a specially designed coil to maximize the system’s latent capability, thus yielding 3 to 4 times the moisture removal capacity over a standard air conditioning system.
- The system helps to eliminate high load nuisance service trips by re-balancing the refrigerant system.
ExpertAire™ is available in one of the following five configurations: