Ventilation Control; Supply Fan Compensation; Outdoor Air Minimum Position Control - Trane Symbio 700 Controller Application Manual

Table 5. Sensor data (continued)
When conditions are suitable for economizer operation, the outdoor air damper modulates between a
calculated outdoor air damper minimum position (based on Supply Fan Compensation and Demand
Controlled Ventilation) and 100% open. Economizing will not allow additional mechanical cooling until
the damper position is 100% and supply fan has reached 100% capacity for 5 minutes. If economizer
cooling becomes disabled, the damper will revert to minimum position control, and transition to
mechanical cooling.
A building automation system can directly command economizer operation via Economizer Airside
Enable (auto, enable, disable). If commanded Enable, the controller will start economizer cooling,
regardless of outdoor air conditions. If commanded Disable, economizer cooling will be disabled (except
if a mode of Night Purge is commanded to the controller). If commanded Auto, the controller will use the
configured Economizer high limit method and input values to determine if economizer cooling is
available.

Ventilation Control

On equipment installed with a 0 to 100% Economizer Damper, the Symbio™ 700 will control the outdoor
air damper to provide minimum ventilation requirements based on the specific options installed, enabled
features and mode of operation. During normal occupied periods of heating and cooling modes of
operation, the outdoor air damper maintains ventilation requirements. However, the following modes of
operation will override the damper minimum position setpoint to 0%.
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Supply Fan Compensation

The outdoor air damper minimum position is modulated to provide outdoor air based on supply fan
speed. When the supply fan increases speed, the outdoor air damper minimum position is reduced to
prevent over ventilation. When the supply fan decreases speed the outdoor air damper minimum
position is increased to maintain design outdoor air requirements. There are three user editable design
minimum settings to linearize damper position with the fan curve during Occupied and Occupied Bypass
modes of operation.
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•
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There are three additional user editable design minimum settings for Occupied-Standby mode of
operation.
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Outdoor Air Minimum Position Control

If Supply Fan Compensation is disabled. This function provides a fixed damper position for minimum
outdoor air requirements. The damper is controlled to a position determined by Economizer Minimum
Position Setpoint.
ACC-APG002A-EN
Economizer Enable Method
Morning Warm Up
PreCool
Night Purge
Unoccupied Heat
Unoccupied Cool
Off
Design Minimum OA Damper Position at Min Fan Capacity (25% default)
Design Minimum OA Damper Position at Mid Fan Capacity (15% default)
Design Minimum OA Damper Position at Full Fan Capacity (10% default)
Standby Minimum OA Damper Position at Min Fan Capacity (25% default)
Standby Minimum OA Damper Position at Mid Fan Capacity (15% default)
Standby Minimum OA Damper Position at Full Fan Capacity (10% default)
Outdoor Air Damper Control
Required Sensor Data
Return Air Temperature
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