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| Overview

The DAB terminal profile is a profile that controls the terminal equipment of a space, which is provided by an RTU or an AHU for its HVAC needs.

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The profile is supported by a SmartNode, Smart Damper, and a Smart Damper Actuator to provide the necessary control outputs based on the profile configured.

| How it Works

75F Dynamic Airflow Balancing operates to help temperature balance a system without fully closing off zones and creating harmful back pressure on the AHU.

Once you select the DAB terminal profile under SmartNode DAB profiles, the configuration provides the options to define the damper types, size, shape, and zone priority. It also provides the options to define the minimum and maximum damper positions during heating and cooling along with the Temperature Offset.

Additionally, the profile provides options to modify the controls based on the Internal Air Quality and Co2, with the IAQ and Co2 control that can be enabled or disabled.

Normally the Algorithm continuously tracks the current temperature of the zone and looks for the change in the difference between the terminal level Desired Temperature and Current Temperature and provides an optimal damper opening position within the deadband range, which is a resultant of the loop output based on the PI loop for control signals.

When the Current Temperature increases above the set point or desired temperature, the zone calls for cooling from the system or building-level equipment. 

And when the Current Temperature decreases below the set point or desired temperature, the zones call for Heating from the system or building-level equipment.

The building or system-level device is an RTU or AHU which is controlled by the system-level DAB profiles.

For more information on the system-level DAB, profiles refer below.

DAB Staged RTU - Wiring/ Configuration

VAV Staged RTU w/ VFD Fan

DAB Fully Modulating AHU - Wiring/ Configuration

DAB Modulating AHU with DCWB

DAB Advanced Hybrid AHU - Wiring/ Configuration

When the Co2 or the IAQ control is enabled, the algorithm takes the target and threshold values of Co2 and VOC into consideration. An increase in the value from the threshold value results in a loop output, and it changes the minimum damper position for the actual control to the changes in percentage value.

This resultant loop output is called the Co2 loop output, which is simply the weighted average Co2 loop output for all the zones that have Co2 control enabled.

Example- If the target and threshold are 1000ppm and 800, measured Co2 is 850 and configured damper limits are 0-100.  The algorithm starts raising the minimum damper position proportionally from 800.  A Co2 measurement of 850 will yield a loop output of 25%. This raises the damper's min position so that it now varies in the range of 25 – 100 based on temperature.

 

| Wiring

Below is a wiring schematic for the DAB terminal profile, that shows the connection between the SmartNode, Damper Actuator, and the Damper.

A Temperature and Humidity only sensor, which can be a Wall Sensor/Ceiling Sensor/Duct Sensor/Flush Mount Sensor is connected to the RTS port of the SmartNode.

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Points to be considered while wiring

When installing a Belimo actuator, use the 18gauge thermostat wire for connections between Smart Node and Actuator. 

For the sensors, both ends of the harness are the same male connectors. Plug one end into the Wall Sensor. Plug the other end into the RTS port on the Smart Node.

| Configuration

Below is the configuration screen for the DAB terminal profile.

Once you've paired the Smart Node as a DAB profile, and once a few specific configuration parameters that define the physical characteristics of the setup are set in the configuration screen, the 75F sequence for the DAB will influence and control the setup. 

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Damper Type

Following are the damper types the 75F system supports

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Damper 1 Type

Type of actuator being controlled on Damper port 1 or Analog out 1. 75F Smart Dampers is controlled using an MAT actuator through Damper port 1. If you are using a modulating 0-10Vdc type, then Damper 1 Type will be Analog Out 1 and will read TH1 for the DAT. 

Damper 2 Type

Type of actuator being controlled on Damper port 2 or Analog out 2. 75F Smart Dampers are controlled using an MAT actuator through Damper port 2. If you are using a modulating 0-10Vdc type, then Damper 2 Type will be Analog Out 2 and will read TH2 for the DAT. 

Size -Size of the associated damper. Used for calculating CFM. 

Shape - Shape of the associated damper. Also used for calculating CFM.

Zone Priority -Used in calculations for driving the AHU into heating or cooling. (Low = 1, Normal = 10, High = 50) 

Enable IAQ Control -Must have an IAQ sensor present. Nonstandard option.

Enable Co2 Control - Must have a Co2 sensor present. Nonstandard option. 

Enable Occupancy Control - Must have an Occupancy Sensor present. Nonstandard option. 

Enable CFM- To enable operation based on the Airflow in cubic feet per minute calculation. For more information refer to True CFM (Cubic Feet per Minute)

Temperature Offset -Value applied to the current temperature reading if the current temperature needs calibration. Sensors should not typically need calibration. 

Min/ Max Damper Positions -Hard limits on damper positions in a given mode. 

| Operation

Considering there is more than one terminal profile connected to the DAB system profile when the zones are within the deadband the damper positions are managed using the terminal level loop output.

When the temperatures cross the Deadband and zones call for cooling or heating from the system level equipment, the cooling or heating which the system level equipment provides is divided optimally for the zones, to help temperature balance a system without fully closing off zones and creating harmful back pressure on the AHU. This is achieved based on two approaches.

  • Normalization
     
  • Minimum overall Damper Position
     

Which is based on the DAB profile sequences and uses the aspects like the Zone priority, Damper size, and other tuner parameters for the output calculations.

 

 

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