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which needs to be reheated.
• If neither the air (such as when in cooling mode) nor the water needs heat, it will
be rejected to the remote outdoor condenser.
• If no outdoor condenser is available, the compressor will shut off rather than
overhaul the room air. Although the system cannot dehumidify the air when its
compressors are off, overheating the space is unacceptable because it will cause
occupant discomfort.
• For this same reason, the compressor can start and run on a call for air cooling if
another heat sink is available.
The Desert Aire SP senses the temperature and relative humidity of the air entering the
evaporator and uses this data to determine the unit mode of operation.
The modes of operation are unoccupied, occupied, event, max outside air and purge mode.
• Unoccupied Mode
In the Unoccupied mode, typically outdoor air dampers will be closed and a very
small amount of exhaust air is extracted from the building in order to ensure the
space is negatively pressurized. When a Low Exhaust option is selected, the
Unoccupied mode can be configured to bring in low flow rate of outdoor air in
order to offset any amount of exhaust that may be extracted from this separate
system. Unoccupied mode is engaged when no other mode is presently engaged.
• Occupied Mode
This mode is used when a typical amount of occupancy in the space is to be
encountered. Occupancy can be commanded with any of the following:
Internal Occupancy Schedule via an integral seven-day programmable time
clock, a contact closure, or through a Building Management System (BMS)
network.
• Event Mode
This mode is typically used to signal the unit to bring in greater amounts of
outdoor air when spectators are expected to be present. The mode can be
activated through a dry contact closure or Building Management System (BMS)
network. Note that the Occupied mode must be engaged when Event mode is
commanded or no change will occur.
• Max OA Mode
Max OA mode is typically used to signal the unit to bring in a very high level of
outdoor air under specific circumstances. The economizer feature includes
outdoor sensors to monitor the OA condition. When the outdoor conditions are
appropriate; to reduce the temperature and/or humidity, the unit will index to MAX
OA mode automatically. Additionally, if equipped with a VOC monitor option, and
the VOC reading from the sensor exceeds the set point, the unit will index to Max
Desert Aire - SP Manual
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