RTU
The CO2 demand controlled ventilation (DCV) operation improves indoor air quality in the zone by monitoring CO2 levels. When the CO2 level in an individual exceeds its CO2 setpoint, the zone coordinator increases the minimum position of the economizer damper by 5% every 30 minutes. After the zone has fallen below the setpoint for 5 minutes, the coordinator decreases the economizer minimum position by 5% every 30 minutes. The economizer minimum position does not exceed the user-set maximum ventilation damper position (Demand Ventilation Maximum Damper Position) but returns to the user-set Economizer Minimum Position Setpoint. The 30-minute time period is reduced to two minutes when the Title 24 Test Mode parameter is set to True.
VAV box
When Demand Ventilation Mode of Operation is set to CO2 and a CO2 sensor is operational, the DCV minimum damper flows (DCV Occupied Cooling Min Flow and DCV Occupied Heating Min Flow) are proportionally reset based on a CO2 setpoint and a CO2 proportional band. The value that the damper minimum flows are reset to do not exceed the user-set minimum value (DCV Max Flow). DCV supports up to four CO2 sensors. The CO2 sensor with the highest value is used to determine the reset value. If all CO2 sensors are unreliable, the system uses the Occupied Cooling Min Flow and Occupied Heating Min Flow parameter values.