Desert Aire Aura QS, Installation And Operation Manual

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5.3 Recommended Controller Settings
It is important to determine your comfort set points and to avoid further controller adjustments.
It takes time for the unit to establish equilibrium at a given set point. Therefore, continued
set point adjustments will lead to high energy consumption and user discomfort. Continuous
blower operation is recommended. This will reduce air stratification and assure that the
refrigeration circuit is activated only when it is necessary.
RECOMMENDED SET POINT:
• Humidity: Typical dewpoint set points range from 50°F to 60°F. Consult the Building
Design Engineer for appropriate setting for specific application.
• Normal Suction Pressure Range (R-410A) 100 to 155 PSIG
• Normal Discharge Pressure Range (R410A) 290 to 480 PSIG
5.4 IAQ Sequence of Operation
5.4.1 Basic Sequence
In the past, the industry has had difficulty in providing controlled supply air. System
short-cycling, overcooling or overheating of the space, and lack of a fine tuned reheat /
cooling loop have been major issues. During the original conception of our IAQ products,
Desert Aire took these issues into consideration and incorporated a unique solution, as
well as a unique heat pump design. The following sequence of operation will provide a
detailed description of the unit controls and also explain the heat pump design.
All Desert Aire IAQ products sense the temperature and relative humidity of the air
entering the evaporator and use this data as the process variable to determine the unit
mode of operation. On IAQ units without an energy recovery device (enthalpy wheel),
the sensing point is downstream of the filter rack. On those QS units that include an
energy recovery device, the sensing point is downstream of the filter rack and the energy
recovery device. Desert Aire refers to this point as the Intake Air, or IA. This sensing
point provides for stable unit operation and ensures that air delivered to the supply is less
than the design dewpoint. In the case of QS units with energy recovery components
upstream of the evaporator, sensing the IA at this point also provides the advantage of
disabling the compressors periodically.
Desert Aire has standardized a control program that features two subroutines. These two
subroutines act independently of each other, but together provide for precise humidity and
temperature control. The first subroutine determines the basic mode of operation –
heating, cooling, or dehumidification. Measuring the IA temperature and humidity will
determine the mode. The second subroutine controls the supply air temperature (SAT),
which is done by measuring the SAT in the supply air ductwork.
Desert Aire - QS/QV Manual