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These setpoint limits apply only to the occupied and occupied standby, heating and cooling setpoints.
They do not apply to the unoccupied heating and cooling setpoints. When the controller is in the
unoccupied mode, it always uses the unoccupied heating and cooling setpoints. Unit configuration
enables or disables the local (hard-wired) setpoint. This parameter provides additional flexibility to allow
the user to apply communicated, hard wired, or default setpoints without making physical changes to
the unit. Similar to hard-wired setpoints, the effective setpoint value for a communicated setpoint is
determined based on the stored default setpoints, configuration values, and the controller occupancy
mode.
Setup Parameters Screen
Device
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VAV Setup
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Ventilation Setup
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Space CO
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BAS-SVX091A-EN
Wireless Sensor Enable/Disable: Enables controllers to use wireless sensors in conjunction with a
Wireless Communication Interface (WCI) [enabled by default]. When unchecked, only wired sensors
or wireless sensors using Wireless Receiver Modules (WRM) are allowed.
Space Temperature Source: The drop-down menu is used to select the source of the controllers
space temperature value. Choices are Local Source and BAS.
Occupancy Request Source: The drop-down menu is used to select the source of the controllers
Occupancy Request. Choices are Local Source and BAS.
Airflow Nominal Status: Nominal flow is the total airflow capacity of the VAV box. Nominal Flow
becomes an active field when Generic is selected in Box Size under Equipment Options on the
Configuration page. Select the CFM nominal flow for the unit. This is normally used when mounting
the Symbio 500 controller on someone else's VAV unit.
Unit Flow Gain: The flow gain is a multiplier used to calibrate the value reported by the flow sensor
so that the reported airflow matches the actual airflow. Typically, it is not necessary to change this
value. For Trane units, the nominal airflow and unit flow gain are based on unit size and are not
adjustable. The default unit flow gain for generic VAV boxes is 1.0.
Airflow Measurement Offset: The flow offset is used to calibrate the value reported by the flow
sensor so that the reported flow matches the actual flow. The flow offset is determined during the air
balancing process. A test-and-balance professional will use the Tracer TU Air and Water Balance
tool to calculate this value and balance the VAV box. Typically, it is not necessary to change this
value.
Note: The flow offset is calculated only for two-point balancing, which requires reading both the
maximum and minimum airflows during balancing. Two-point balancing ensures greater
accuracy over the entire range of air valve operation.
Airflow Gain: The airflow gain is used to calibrate the value reported by the flow sensor so that the
reported airflow matches the actual airflow. The flow gain is determined during the air balancing
process. A test-and-balance professional will use the TU Air and Water Balance tool to calculate this
value and balance the VAV box. Typically, it is not necessary to change this value.
Ventilation Setpoint Local: The Tracer SC+ BAS uses the ventilation setpoint from all the VAV
boxes to calculate how much outdoor air (OA) the system needs. During the occupied mode, this
setpoint is the active setpoint for ventilation, and should be equal to the ventilation airflow required at
design occupancy of the space.
Ventilation Standby Setpoint: During the occupied standby mode, this setpoint is the active
setpoint for ventilation.
Setup
2
Space CO
Low Limit: The controller adjusts the ventilation setpoint based on the current CO2
2
concentration. When the concentration is less than or equal to this low limit, the zone is most likely
unoccupied and the ventilation setpoint is set equal to Ventilation Standby Setpoint. When the
concentration is between the low and high limits, the ventilation setpoint is adjusted proportionally
between Ventilation Standby Setpoint and Ventilation Setpoint Local.
Controller Points and Parameters
41
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Troubleshooting
