Trane IntelliPak SCRF 25, Инструкция по установке, эксплуатации и обслуживанию

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SCXF-SVX01Q-EN 67
setpoint to modify the volume (cfm) of fresh air
entering the unit as the measured airflow deviates from
setpoint.
When the optional preheat temperature sensor is
installed at the auxiliary temperature on the VCM and
the preheat function is enabled, the sensor will monitor
the combined (averaged) fresh air and return air
temperatures. As this mixed air temperature falls
below the preheat actuate temperature setpoint, the
VCM activates the preheat binary output to control a
field-installed heater. The output deactivates when the
temperature rises 5°F above the preheat actuate
temperature setpoint.
Using a field-installed CO
2
sensor with CO
2
reset
enabled, as the CO
2
concentration increases above the
CO
2
reset start value, the VCM modifies the minimum
outside air cfm setpoint to increase the amount of fresh
air entering the unit. The setpoint adjusts upward until
reaching the CO
2
maximum reset value. The maximum
effective (reset) setpoint value for fresh air is limited to
the system’s operating cfm. As the CO
2
concentration
decreases, the effective (reset) setpoint value adjusts
downward toward the minimum outside air cfm
setpoint. See CO
2
reset figure below for an airflow cfm
vs. CO
2
concentration curve.
Figure 35. CO
2
reset function, outside air vs. CO
2
Increasing
Concentration
Carbon Dioxide Reset
Maximum
Airflow
Increasing
Reset Amount
O.A CFM
Setpoint
Carbon Dioxide
Reset Start
Carbon Dioxide
Maximum Reset
Standard Two-Position Damper Interface
Units with the two-position damper interface are
provided with a 0-10 VDC control output suitable for
controlling a field-provided modulating actuator. In
occupied mode, the output drives to the maximum
position.
Airside Economizer Interface
Units with airside economizer interface are equipped
with the necessary control sequences to allow using
outside air for first stage of cooling, in occupied or
unoccupied mode and when ambient conditions are
favorable for economizing. Inherent in unit controller is
the ability to suppress setpoint below 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. 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 2-10VDC 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).
Air-Cooled Condensers
Model SXRFunits are designed for use with the remote
air-cooled condenser, model CXRC. For more
information, see the Installation, Owner, and
Maintenance Manual for Air-cooled Condenser,
CXRC-
SVX01*-EN . See for CXRC refrigerant connection sizes.
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.
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