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SCXG-SVX01B-EN 81
peak operating efficiency. An outside air
temperature and relative humidity
sensor are provided for field installation
to monitor reference enthalpy.
Economizer operation enables when the
outside air enthalpy is less than 25 BTu/lb
(adjustable 19-28 BTu/lb.). During
occupied mode, the outside air damper
opens to 15% (adjustable 0-100%) for
ventilation purposes. Also, the ability to
alter the outside air damper position to
compensate for VAV supply air
modulation is inherent in the unit controls,
and can be enabled by the operator. An
analog 2-10 VDC output (adjustable (0-10
VDC) is provided to modulate the field-
provided 30 second damper actuators
(adjustable 1-255 seconds).
Airside Economizer Interface with
Comparative Enthalpy
Units with airside economizer interface
and comparative enthalpy are equipped
with the necessary control sequences to
allow using outside air for the first stage
of cooling, in occupied or unoccupied
mode and when ambient conditions are
favorable for economizing. Inherent in the
unit controller is the ability to suppress
the setpoint below the normal unit
setpoint. This allows the building to
improve comfort levels when possible,
and at the same time, optimize building
mechanical cooling operation for peak
operating efficiency. A factory-installed
control board, with outside and return air
temperature and relative humidity
sensors, are provided for monitoring
outside and return air. The sensors are
field installed. Economizer operation
enables when the outside air enthalpy is
3 BTU’s/lb. less than the return air
enthalpy. During occupied mode, the
outside air damper opens to 15%
(adjustable 0-100%) for ventilation
purposes. Also, the ability to alter the
outside air damper position to
compensate for VAV supply air
modulation is inherent in the unit
controls, and can be enabled by the
operator. An analog 2-10 VDC output
(adjustable (0-10 VDC) is provided to
modulate the field-provided 30-second
damper actuators (adjustable 1-255
seconds).
Figure O-GI-6. CO
2
reset function, outside air vs. CO
2
general
information
Air-Cooled Condensers
Model SXRF units are designed for use
with the remote air-cooled condenser,
model CXRC. For more information, see
the air-cooled condenser Installation,
Owner, and Diagnostic Manual,
CXRC-
SVX01A-EN.
Condenser fans will stage per a user-
defined setting. If the condenser is
equipped with head pressure control (air
modulation on last stage of condenser
capacity), the condenser airflow will
modulate to maintain condensing
temperature setpoint. Condensing
temperature is determined by sensors
located at each condenser coil.
Operation