26
Position in Effect (EFFECTIVE MIN POS) relationship while the
Commanded Fan Speed (ECON CMD POSITION) is held at the
maximum speed.
ANALOG IAQ CTRL = 2 (Override IAQ)
Override IAQ is reserved for a future release.
ANALOG IAQ CTRL = 3 (Control Minimum Position)
An external 4 to 20 mA source is used to set the Min Position in
Effect (EFFECTIVE MIN POS). The 4mA signal corresponds to
0% and the 20 mA signal corresponds to 100%. In this mode,
configuration such as Economizer minimum at maximum fan
speed (MIN POS @ MAX FAN), IAQ position at maximum fan
speed (IAQ POS @ MAX SPD) and the economizer minimum
position and DCV minimum position curves in Fig. 16 and Fig. 18
are not used. If the indoor fan is not operating, the economizer
position will be zero. The actual damper position may exceed the
economizer Min Position in Effect (EFFECTIVE MIN POS) to
provide economizer cooling.
VENTILATION FOR PEOPLE
VENTILATION FOR SOURCES
INCREASING VENTILATION
MIN POS @
MAX FAN
IAQ POS @
MAX FAN
100 700 INSIDE/OUTSIDE CO
2
DIFFERENTIAL
LOW AIR.Q DIFF HIGH AIR.Q FIFF
C14328
Fig. 18 -- Example
Outdoor Air Quality (Analog Input)
The default for the Outdoor Air Quality (OAQ LEVEL) is 400
ppm CO
2
when the OAQ sensor is not assigned an input channel.
When OAQ Assigned channel (OAQ SENSOR CHAN) is set for
an analog input that input channel will be mapped to the Outdoor
Air Quality (OAQ LEVEL). The outdoor air quality sensor
provides a 4 to 20 mA signal corresponding to 0 to 2000 ppm
CO
2
. If a field supplied sensor has a different range, the ppm
display range must be reconfigured by entering new values for the
OAQ Sensor Value at 4mA (OAQ PPM @ 4MA) and OAQ Sensor
Value at 20mA (OAQ PPM @ 20MA).
Pre-- occupancy Purge
The control has the option for a pre-- occupancy purge to refresh the
air in the space prior to occupancy. This feature is enabled by
setting PREOCC PURGE ENBL to Yes. This function is also
referred to as the IAQ purge function.
The IAQ Purge will operate under the following conditions:
S Purge is enabled
S the unit is in the unoccupied state
S Current Time is valid
S Next Occupied Time is valid
S time is one hour prior to next occupied period
S the OAT is greater than the lockout (PREOCC LOW LIMIT)
The IAQ Purge Position curve is created by applying the difference
of the IAQ purge position at maximum fan speed (PURGE POS @
MAX) and the Economizer minimum at maximum fan speed (MIN
POS @ MAX FAN) in relationship to the minimum position curve.
The IAQ purge position at maximum fan speed (PURGE POS @
MAX) should be set to an economizer position that brings in
enough fresh air over an hour period to remove contaminates and
CO
2
during the unoccupied period. When the preoccupancy purge
function is active (IN PREOCC PURGE?), the economizer Min
Position in Effect (EFFECTIVE MIN POS) will follow the IAQ
Purge Position curve.
Temperature Compensated Start
Space control set points are usually set to 2 different levels for
unoccupied period and occupied period. Unoccupied set points
saves energy, while occupied set points provide occupant comfort.
The time period it takes for the RTU to bring the space from its
current condition in unoccupied mode to its occupied set point is
referred to as start bias time, or bias time. The algorithm to
calculate this bias time is called T emperature Compensated Start.
This is required for ASHRAE 90.1 compliance. When temperature
compensated start is running (TCS ACTIVE?) the control uses the
occupied set points to control the space.
When Temperature compensated start is enabled (ADAPTIVE
TCS?), no other configuration parameters are needed for this
algorithm, because the algorithm will automatically adjust the Bias
Time based on the data collected during the period of last time
optimal start. The inputs to the calculation algorithm includes space
temperature, unoccupied set points, occupied set points, outdoor air
temperature, and supply air temperature. Bias time is changed
dynamically per RTU operation.
When Temperature compensated start is disabled (ADAPTIVE
TCS?), the control will use the User Temperature compensated
Start bias time (USER TCS BIASTIME) in determining when to
start controlling to the occupied set points. If the User Temperature
compensated Start bias time (USER TCS BIASTIME) is set to
zero, the control will switch to the occupied setpoints at the time of
occupancy.
Linkage
The SystemVut controller will support 3Vt, VAV a n d V V T
R
zoning system on a CCN system or Open VVT and VAV systems
on a BACnet MS/TP System. All that is required is to configure
the Open or 3V Master zone to use the SystemVu rooftop unit as
its airsource. The SystemVu control will need to be configured for
the proper network protocol (BAS PROTOCOL) and set for Space
Sensor Control (UNIT CTRL TYPE). The SystemVu controller
will reply to the zoning system and change its operating parameters
to meet the demand of the zoning system. Status of this process can
be viewed in the airside linkage tab of the property pages in the
i-- Vu
R
application or by viewing the linkage maintenance table
with a CCN tool.
Carrier Comfort Network
R
(CCN) Operation
The SystemVu controller can be configured to connect to a CCN
system. The SystemVu controller has one RS--485 BMS port that
can be configured from the local display for BACnet or CCN. The
BMS configuration parameters can be found in the
SETTINGSNETWORK SETTINGS submenu. The first
configuration is the BMS system for CCN systems change this
configuration from BACnet to CCN then set the CCN BAUD rate,
the bus and element number and you will be able to find the
controller with any CCN tool then upload the CCN tables in the
controller for use by the tool.
BACnet Network Operation
The Syste mVut controller is ready to connect to BACnet. The
SystemVu cont rolle r has one RS--485 BMS por t that can be
configure d from the l ocal di s play for BACnet or CCN. The default
setting is BACnet and the Default BACnet Baud rate is 76800. These
settings are found on the SETTINGSNETWORK SETTINGS sub
me nu of the loc al displ ay . Ther e ar e four other s etti ngs for i--Vu
R
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