COBP zone dampers
In occupied mode, if the zone temperature rises above the Occupied Cooling Setpoint, and the system requests cooling, the zone damper uses a pressure dependent strategy to adjust the zone temperature and meet the occupied cooling setpoint. If the system provides heat, the zone damper remains at the satisfied minimum position.
If the zone temperature drops below the Occupied Heating Setpoint, and the system provides cooling, the zone damper remains at its heating minimum position, and the zone damper controller commands supplemental heating and box reheat according to the following table.
| Supplemental heating available | Box reheat available | Operation sequence |
|---|---|---|
| Yes | No | The zone damper controller modulates the supplemental heating to meet the Occupied Heating Setpoint. If supplemental heating is at 100% for more than 5 minutes, and the zone temperature is still below the Occupied Heating Setpoint, the zone damper controller sends a vote to the VZC for heating. |
| No | Yes | The zone damper controller modulates the box reheat to meet the Occupied Heating Setpoint. If box reheat is at 100% for more than 5 minutes, and the zone temperature is still below the Occupied Heating Setpoint, the zone damper controller sends a vote to the VZC for heating. |
| Yes | Yes | The zone damper controller modulates the supplemental heating to meet the Occupied Heating Setpoint. If supplemental heating is at 100% for more than 5 minutes, and the zone temperature is still below the Occupied Heating Setpoint, the zone damper controller also modulates the box reheat to meet the Occupied Heating Setpoint. If box reheat is at 100% for more than 5 minutes, and the zone temperature is still below the Occupied Heating Setpoint, the zone damper controller sends a vote to the VZC for heating. |
| No | No | The zone damper controller sends a vote to the VZC for heating. |
If enough votes reach the VZC, and the changeover minimum time allows heating, the VZC commands heating.
When the system provides heating, the zone damper uses a pressure dependent strategy to adjust the zone temperature and meet the Occupied Heating Setpoint. If the system provides cooling, the zone damper remains at its heating minimum position. If the zone temperature is between setpoints, the zone damper is at its satisfied minimum position.
Unoccupied mode operation is identical to occupied mode operation except that the unit adjusts the zone temperature to meet the Unoccupied Cooling Setpoint and Unoccupied Heating Setpoint.
VAV box
In occupied mode, if the zone temperature rises above the occupied cooling setpoint and the system is in a cooling mode, the zone damper uses a pressure independent strategy to adjust the zone temperature to meet the occupied cooling setpoint. If the system provides heating (zone mode = Heating), the zone damper controls the flow to meet the occupied cooling minimum flow (Occupied Cooling Min Flow).
If the zone temperature drops below the occupied heating setpoint, the optional supplemental heat or box reheat is used to adjust the zone temperature to the Occupied Heating setpoint. If the supplemental or box reheat is at maximum capacity but cannot maintain the zone temperature, the zone remains at the heating minimum until the system is in a heating mode. If the system is in a heating mode and if the system provides heating, the damper opens to maximum flow. If the zone mode is set to cooling, the zone damper adjusts to a heating minimum flow if local heat is present.
The zone damper adjusts the flow to the occupied cooling minimum flow (Occupied Cooling Min Flow) when the zone temperature is between the setpoints.
For unoccupied operation, if the temperature rises above or below the unoccupied cooling and unoccupied heating setpoints (Unoccupied Heating Setpoint and Unoccupied Cooling Setpoint), and the system provides air with the correct temperature, the zone damper adjusts to a maximum. For example, the system provides cold air when the zone needs cooling. If the system does not provide air with the correct temperature, the zone damper adjusts the flow to the appropriate minimum flow.