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Access 4.x |
Mixing damper function |
The air quality controller intervenes into the temperature controller's regulation of the damper sequences. In usual installation, the temperature controller tend to open the mixing damper so that more of the extract air could be recirculated and more heating (or cooling) energy saved. The air mixing can be further increased if the airflow of the fresh outdoor air is being regulated simultaneously.
As recirculation continues, the demand for the fresh air increases. The output of the air quality controller rises and forces an opening of the outdoor air and a closing of the mixing dampers.
The temperature controller and the Air quality controller are usually set for reverse acting, meaning that the first regulates damper to close while the second regulates it to open. Access calculates the balance point between outputs of both controllers therefore the damper actuators are constantly adjusting.
The PID regulated Air quality controller has two sequences: "Air quality control sequence 1" and "Air quality control sequence 2". The sequences are regulated up one after another as output of the air quality controller rises. Regulation always starts with "Air quality control sequence 1" and is followed by "Air quality control sequence 2". The order is reversed at reducing controller's output.
The mixing damper function can be used either for CO2 control or for Relative Humidity (RH) control.
In the RH control type there is a risk of unintentional humidity increase due to possibly higher saturated outdoor air. It is recommended to configure Enthalpy control function together with it.
Configuration example for air quality control (CO2) mixing damper function |
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Variable |
Available options & Selection |
Note |
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Activation of the function |
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Configuration > Functions > Function activation |
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Air quality |
... | Mixing damper function | ... |
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Recirculation |
| No | Yes | |
Visibility of the mixing damper in the flowchart |
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Configuration of the air quality control |
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Configuration > Functions > Air quality control |
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Sensor type |
| CO2 | RH | |
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Activation of air quality control for damper sequences |
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Configuration > Functions > Function activation > Heating/Cooling sequence setup > Recirculation 1 (mixing damper) |
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… |
… |
… |
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Type of sequence |
…| Damper |... |
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Air quality control |
| No | | Air quality control sequence 1 | | Air quality control sequence 2 | |
2nd sequence to suppress at rising air quality controller output (Reduce of air mixing) |
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Air quality control mode |
| Decreasing | Increasing | |
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… |
… |
… |
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Configuration > Functions > Function activation > Heating/Cooling sequence setup > Recirculation 2 (outdoor air damper) |
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… |
… |
… |
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Type of sequence |
…| Damper |... |
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Air quality control |
| No | | Air quality control sequence 1 | | Air quality control sequence 2 | |
1st sequence to suppress at rising air quality controller output (Let in more of the fresh air) |
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Air quality control mode |
| Decreasing | Increasing | |
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… |
… |
… |
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Allocation of the CO2 sensor |
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Configuration > I/O allocation settings > Analog inputs |
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CO2 room /extract air |
Any available I/O |
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Operational settings |
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Data & Settings > Demand control > Air quality control |
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CO2 room /extract air |
___ ppm |
Actual CO2 level |
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Setpoint mixing damper CO2 |
[1000] ppm |
Acceptable max CO2 level |
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Graphical representation |
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Flowchart > Mixing damper |
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Output of the Recirculation 1 sequence (mixing damper) 0% - fully closed 55% - partially open 100% - fully open |
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Flowchart > Outdoor air damper |
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Output of the Recirculation 2 sequence (Outdoor air damper) 0% - fully opened 45% - partially closed 100% - fully closed |
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