48 VAV-SVX07F-EN
Calibration, Operation Modes, and Control
Stand-alone Controller Freeze Protection
Controllers operating without communications do not have the source temperature available to
them. In these cases, the discharge air temperature sensor is assumed to provide a reasonable
representation of the coil temperature at conditions with no airflow, if the sensor is close to the coil.
If the discharge air temperature (at no airflow) falls below the configured outdoor air low limit, the
hot water valve is fully opened. The hot water valve remains OPEN until the discharge air
temperature is 10°F above the configured outdoor air low limit or occupied operation begins. If the
communicated source temperature is invalid and the local discharge air temperature sensor has
failed, freeze protection is active and the water valve is open.
Unoccupied Ventilation Flow Control
The controller closes the air valve and the local electric heat and hot water heat are disabled. The
hot water valves OPEN, if needed for freeze protection. The operation of freeze protection for local
hot water heat depends on whether the controller is operating as a network controller or a stand-
alone controller.
Flow Tracking (FTC)
Two (2) UC400 controllers work together to provide flow tracking control (refer to the illustration
below). The space temperature controller (STC) Discharge Air Flow is communicated to the flow
tracking controller and is reported as Air Flow Setpoint BAS.
Note: This must be set up on the Tracer SC using either a global
reference or TGP2 program. for
more details, refer to the Air Systems for Tracer SC Application Guide (BAS-APG007).
The flow tracking controller adds the configured airflow track
ing offset (positive or negative) to the
Air Flow
Setpoint BAS and controls the airflow to this setpoint (Air Flow Setpoint Active). The flow
tracking controller does not require a space temperature sensor or a discharge air temperature
sensor. If the calculated airflow setpoint is less than 10% of the configured nominal airflow, and the
configured airflow tracking offset is less than zero, the air valve is closed. If the calculated airflow
setpoint is less than 10% of the configured nominal airflow, and the configured airflow tracking
offset is greater than or equal to zero, the air valve is positioned at the configured minimum airflow.
The maximum airflow setpoint is limited by the configured maximum airflow.
Figure 7. Using Two UC400 Controllers to Provide Flow Tracking Control
Exhaust
Comm Link
Supply STC VAV
To Other VAVs
or Main
Control Panel
Primary Air
From Main
AHU
Occupied Space
Exhaust FTC VAV
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