LT Series Dehumidifiers
SELF CONTAINED SYSTEM LOW AMBIENT DESIGN
LT (Low Temperature) Series - 19553 Dehumidifiers forLow TemperatureApplications
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PPLICATIONS
Ice RinksWater Treatment Plants
Pumping Stations
Food Storage & Processing L
OW TEMPERATURE MOISTURE REMOVAL
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 under-stood 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 coil iscooled 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 evapora-
tor 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 compres-
sor 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 .In order for a
dehumidifier to continue to remove moisturewithout shortening compressor life (continuous hot gas coupled with high humidity will frost up the evaporator quickly.
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EHUMIDIFICATION DESIGN
The LT Series
dehumidifiers combine numerous design fea-tures into a cost competitive system that removes the
unwanted moisture problem in low load situations.Desert Aire starts with an evaporatorcoil designed specifically for low ambi-
ent moisture removal and then adds
appropriate refrigerant components to
insure long operating life.
bypass), the evaporator coil temperature must be allowed to drop below 32°F (0°C). As the temperature drops, ice will
form on the coil which will restrict the airflow. At some
point, the coil must go through a defrost cycle to melt the ice
allowing it to drain properly while eliminating the air restric-
tion in the evaporator.Amounts of ice build-up are a function of air temperature andit’s corresponding relative humidity. Low temperatures when
