SmartNode DAB Dual Duct

4 Minute Read

| Overview

The 75F® DAD Dual Duct is a custom terminal profile that is introduced to support the VAV dual-duct systems. It consists of an air handling unit that has two coils, a continuously operating cooling coil, and a continuously operating heating coil. 

| Advantages

• The System Dual duct variable air volume (DDVAV) is used to obtain zone-level temperature control by mixing the cold and warm air in various volume combinations.
• The fan used is of a size that anticipates the maximum hot or cold air volume, and not the sum of the instantaneous peaks. 
• With control provided with a customized DAB Dual Duct Terminal zone, we can install 75F products in Buildings that have VAV dual-duct systems.

| How it works

Once you select the DAB Dual duct terminal profile under SmartNode DAB profiles, the configuration provides the options to define the damper actuator types for the analog outputs, made available from the SmartNode for controlled output.

Additionally, the profile provides options to modify the controls based on the Internal Air Quality, CO2, and occupancy, with the IAQ, CO2, and Occupancy controls that can be enabled or disabled.

The Algorithm continuously tracks the current temperature of the zone and looks for a 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 result 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 the cooling coil of the system-level device supplies via the Cooling Deck to support the zone.

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, and the heating coil of the system-level device supplies via the Heating Deck to support the zone.

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 are referred to 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.

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 Dual duct terminal profile, that shows the connection from the SmartNode to the Airflow and Reheats damper actuators.

| Configuration Steps

To configure a DAB Dual Duct Profile.

• Click the pair module from the floor layout screen.

• Click the SN (SmartNode) from the select device type, screen.

 

• Click the DAB from the select module type, screen.

• Select the DAB DUAL DUCT under DAB.

 

• Click Pair, to pair the device using the pairing instructions on the pairing steps screen.

• Select the device MAC address relayed for pairing, or click connect manually to pair the device manually. For more information on manual pairing refer to Alternate/ Manual Pairing for SmartNode.

• Enter the pin displayed on the SmartNode device or an automatic pairing.
• Click Pair.

Below is the configuration screen for the DAB Dual duct terminal profile.

Once you've paired the SmartNode as a DAB Dual duct 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.

Analog-out1- set to 'Composite Damper Actuator' by default 

Drop Down Options include Not Used, Composite Damper Actuator, Cooling Damper Actuator, Heating Damper Actuator

Analog-out2- set to 'Not Used' by default 

Drop Down Options include Not Used, Composite Damper Actuator, Cooling Damper Actuator, Heating Damper Actuator

Thermistor-1- connects to Discharge airflow 10K sensor 

Thermistor-2- connects to Supply Air Temperature 

Optionally differential pressure sensor connects to the SmartNode sensor bus 

Optionally SmartSense connects to the RS 485 port to provide CO2, IAQ, and occupancy sensing 

Below the profile configuration, you can program the output voltage for the modulating equipment configured.

| Operation

The cooling coil feeds chilled air into a cold air duct and the heating coil feeds hot air into a hot air duct; the ducts run parallelly throughout the building. The air is tapped from the two ducts by a terminal unit at each space. The terminal unit can have a hot or cold air damper. When the zone requires heating, the hot air damper opens. When cooling is required, the cold air damper opens.

| Sequence of Operation

The sequence of operation is completely driven based on Occupancy mode,  Space Current Temperature, the set Cooling and Heating Desired Temperatures, CFM, and Space CO2 & VOC levels.

Let us understand the Sequence of operations based on the occupancy modes, and how the other factors contribute to the sequence of operations during different types of occupancy modes.

| Occupancy Modes

The occupancy mode (Occupied or Unoccupied) shall be determined through a user-adjustable, graphical, seven-day schedule with a holiday schedule, alongside the configurable autoaway and forced occupied options (external schedule influencers) for optimized controls and enhanced energy savings.

Based on the above aspects factoring into the occupancy the following can be the possible applicable occupancy modes:

• • Pre- Conditioning
  • Occupied
  • Unoccupied
  • Auto-Away
  • Forced Occupied

| Sequence of Operation During Pre-Conditioning

Pre-conditioning is a state just before the building enters the scheduled occupancy. It starts at more like the unoccupied state, the desired temperatures drift to unoccupied setbacks.

The preconditioning uses an algorithm to start the conditioning before the building schedule, from the heating side or cooling side, to bring the building to an optimum level ( within the occupied heating & cooling desired temperatures) exactly at the time of occupancy start.

The zones would operate as shown below to accommodate the preconditioning from the system equipment.

A coolingPreconditioningRate and heatingPreconditiningRate tuners defaulted to 15 minutes, are used alongside the occupied heating/cooling desired temperature breach to determine when the pre-conditioning should start.

Example Calculation:

When,

• • The heating & cooling desired temperatures are 70F and 74F for the building,
  • The current temperature is 76F (Average of zone temperatures),
  • 8:00 AM is the time the building is scheduled to be occupied.

Then the preconditioning start time is calculated as follows:

Cooling Desired Temperature Breach= 76-74=2F

Preconditioning duration= coolingPreconditioningRate (mins) * Cooling Desired Temperature Breach

                                        = 15*2

                                        = 30 mins

The preconditioning starts 30 minutes before the building is scheduled to be occupied, which is = 7:30 AM

During Warm-up:

• • If the space temperature is below the occupied heating desired temperature, the space utilizes the warm-up via HeatingLoopOutput as below.

If System Equipment in Cooling Mode	If System Equipment in Heating Mode
The Damper remains at a minimum	The HeatingLoopOutput is mapped to the Damper position actuator For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

• • The CO2 and IAQ loops are disabled. (If configured for)
  • The CFM loop is disabled. (If configured for)

During Pre-cooling:

• • If the space temperature is below the occupied cooling desired temperature, the space utilizes the morning pre-cooling via CoolingLoopOutput, as below.

If System Equipment in Cooling Mode	If System Equipment in Heating Mode
The CoolingLoopOutput is mapped to the Damper position actuator for the damper position between the min-max damper position cooling. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation	The Damper position moves to the minimum position

• The CO2 and IAQ loops are disabled. (If configured for)

| Sequence of Operation During Occupied

At all occupied times: (based on a set schedule)

• The device maintains a space temperature within the Heating Desired Temperature and Cooling Desired Temperature Range.

During Deadband:

During deadband, the damper operation is influenced, based on the configuration of the profile, as follows.

Configuration	Damper Operation
If only the zone temperature-based configuration is enabled.	The damper shall be at its minimum position and the reheat valve will remain closed. The Dmaper minimum is decided based on the last known conditioning, If the zone reaches deadband from the heating side the Heating Damper Minimum is considered.  If the zone reaches deadband from the Cooling side the Cooling Damper Minimum is considered.
If zone Temperature & CO2-based configuration is enabled.	The Damper position is driven based on the Zone CO2 levels. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation Note: It is possible and likely that temperature control will not be as good when IAQ controls override the damper position. This is indicated by the iaqOverridingDamper being set to true.
If zone Temperature & VOC-based configuration is enabled.	The Damper position is driven based on the Zone VOC levels. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation Note: It is possible and likely that temperature control will not be as good when IAQ controls override the damper position. This is indicated by the iaqOverridingDamper being set to true.
If zone Temperature & CFM-based configuration is enabled.	The Damper position is driven based on the min-max CFM set. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation
If zone Temperature,  IAQ(CO2 & VOC) & CFM-based configuration is enabled.	The Damper position is driven based on Temperaue, IAQ, and CFM. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

 

During Heating:

• • When the space current temperature falls below the HeatingDesiredTemperature the HeatingLoopOutput is enabled as below as below.

If System Equipment is in Cooling Mode

If System Equipment in Heating Mode

The Damper remains at a minimum from 0% - 50% of the Heating Loop Output, till a maximum Discharge Air Temperature (DAT) is reached, defined by the reheatZoneMaxDischargeTemp tuner (90) Then the Reheat loop output is enabled, based on the DAT set point and actual DAT for the loop output calculation. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

The HeatingLoopOutput is mapped to the Damper position actuator and further to modulating reheat or reheat stages. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

• • When the space CO2 & IAQ levels are above the thresholds the CO2/ IAQ loop Outputs drive the damper actuator for damper position. for more information refer to DAB Terminal Profile- Damper Position Calculation & Operation

• • The CFM loop is disabled. (If configured for)

During Cooling:

• • When the space current temperature is above the Cooling Desired Temperature the CoolingLoopOutput is enabled, as below

If System Equipment in Cooling Mode

If System Equipment in Heating Mode

The CoolingLoopOutput is mapped to the Damper position actuator for the damper position between the min-max damper position cooling. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation The CFM loop is enabled  (If configured for) which is mapped to the Damper position actuator for more information on the CFM influence on the operation refer to DAB Terminal Profile- Damper Position Calculation & Operation

The Damper position moves to the minimum position, not allowing further hot air into the room. The Active airflow setpoint will be no higher than the minimum endpoint (minimum Cfm)

• • When the space CO2 & IAQ levels are above the thresholds the CO2/ IAQ loop Outputs drive the damper actuator for the damper position. for more information refer to DAB Terminal Profile- Damper Position Calculation & Operation

Note: The fan runs wherever the zone is occupied and when the reheat is enabled.

| Sequence of Operation During Autoaway

• • The range of Heating Desired Temperature and Cooling Desired Temperature drifts further away.
  • The device maintains a space temperature within the newly set Heating Desired Temperature and Cooling Desired Temperature Range.

During Deadband:

• • CoolingLoopOutput, HeatingLoopOutput, CFM LoopOutput, CO2 and IAQ Loop Output, and Reheat Stages are disabled.

During Heating:

• • When the space current temperature falls below the heating autoaway setback temperature, the HeatingLoopOutput is enabled as below.

If System Equipment in Cooling Mode

If System Equipment in Heating Mode

The Damper remains at a minimum from 0% - 50% of the Heating Loop Output, till a maximum Discharge Air Temperature (DAT) is reached, defined by the reheatZoneMaxDischargeTemp tuner (90) Then the Reheat loop output is enabled, based on the DAT set point and actual DAT for the loop output calculation. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

The HeatingLoopOutput is mapped to the Damper position actuator and further to modulating reheat or reheat stages. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

• • The CO2 and IAQ loops are disabled. (If configured for)
  • The CFM loop is disabled. (If configured for)

During Cooling:

• • When the space current is above the cooling autoaway setback temperature, the CoolingLoopOutput is enabled, as below.

If System Equipment in Cooling Mode

If System Equipment in Heating Mode

The CoolingLoopOutput is mapped to the Damper position actuator for the damper position between the min-max damper position cooling. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation The CFM loop is enabled  (If configured for) which is mapped to the Damper position actuator for more information on the CFM influence on the operation refer to DAB Terminal Profile- Damper Position Calculation & Operation

The Damper position moves to the minimum position, not allowing further hot air into the room. The Active airflow setpoint will be no higher than the minimum endpoint (minimum Cfm)

• • The CO2 and IAQ loops are disabled. (If configured for)

Note: The fan runs wherever the zone is occupied and when the reheat is enabled.

| Sequence of Operation During Unoccupied

• • The range of Heating Desired Temperature and Cooling Desired Temperature drifts further away.
  • The device maintains a space temperature within the newly set Heating Desired Temperature and Cooling Desired Temperature Range.

During Deadband:

During deadband, the damper operation is influenced, based on the configuration of the profile, as follows.

Configuration	Damper Operation
If only the zone temperature-based configuration is enabled.	The damper shall be at its minimum position and the reheat valve will remain closed. The Dmaper minimum is decided based on the last known conditioning, If the zone reaches deadband from the heating side the Heating Damper Minimum is considered.  If the zone reaches deadband from the Cooling side the Cooling Damper Minimum is considered.
If zone Temperature & CO2-based configuration is enabled.	The Damper position is driven based on the Zone CO2 levels. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation Note: It is possible and likely that temperature control will not be as good when IAQ controls override the damper position. This is indicated by the iaqOverridingDamper being set to true.
If zone Temperature & VOC-based configuration is enabled.	The Damper position is driven based on the Zone VOC levels. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation Note: It is possible and likely that temperature control will not be as good when IAQ controls override the damper position. This is indicated by the iaqOverridingDamper being set to true.
If zone Temperature & CFM-based configuration is enabled.	The Damper position is driven based on the min-max CFM set. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation
If zone Temperature,  IAQ(CO2 & VOC) & CFM-based configuration is enabled.	The Damper position is driven based on Temperaue, IAQ, and CFM. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

During Heating:

• • When the space's current temperature falls below the heating unoccupied setback temperature, the HeatingLoopOutput is enabled as below.

If System Equipment in Cooling Mode

If System Equipment in Heating Mode

The Damper remains at a minimum from 0% - 50% of the Heating Loop Output, till a maximum Discharge Air Temperature (DAT) is reached, defined by the reheatZoneMaxDischargeTemp tuner (90) Then the Reheat loop output is enabled, based on the DAT set point and actual DAT for the loop output calculation. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

The HeatingLoopOutput is mapped to the Damper position actuator and further to modulating reheat or reheat stages. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

• • The CO2 and IAQ loops are disabled. (If configured for)
  • The CFM loop is disabled. (If configured for)

During Cooling:

• • When the space current temperature is above the cooling unoccupied setback temperature, the CoolingLoopOutput is enabled, as below.

If System Equipment in Cooling Mode

If System Equipment in Heating Mode

The CoolingLoopOutput is mapped to the Damper position actuator for the damper position between the min-max damper position cooling. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation The CFM loop is enabled  (If configured for) which is mapped to the Damper position actuator for more information on the CFM influence on the operation refer to DAB Terminal Profile- Damper Position Calculation & Operation

The Damper position moves to the minimum position, not allowing further hot air into the room. The Active airflow setpoint will be no higher than the minimum endpoint (minimum Cfm)

• • The CO2 and IAQ loops are disabled. (If configured for)

Note: The fan runs wherever the zone is occupied and when the reheat is enabled.

| Sequence of Operation During Forced Occupied

• • The device maintains a space temperature within the Heating Desired Temperature and Cooling Desired Temperature Range.

During Deadband:

During deadband, the damper operation is influenced, based on the configuration of the profile, as follows.

Configuration	Damper Operation
If only the zone temperature-based configuration is enabled.	The damper shall be at its minimum position and the reheat valve will remain closed. The Dmaper minimum is decided based on the last known conditioning, If the zone reaches deadband from the heating side the Heating Damper Minimum is considered.  If the zone reaches deadband from the Cooling side the Cooling Damper Minimum is considered.
If zone Temperature & CO2-based configuration is enabled.	The Damper position is driven based on the Zone CO2 levels. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation Note: It is possible and likely that temperature control will not be as good when IAQ controls override the damper position. This is indicated by the iaqOverridingDamper being set to true.
If zone Temperature & VOC-based configuration is enabled.	The Damper position is driven based on the Zone VOC levels. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation Note: It is possible and likely that temperature control will not be as good when IAQ controls override the damper position. This is indicated by the iaqOverridingDamper being set to true.
If zone Temperature & CFM-based configuration is enabled.	The Damper position is driven based on the min-max CFM set. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation
If zone Temperature,  IAQ(CO2 & VOC) & CFM-based configuration is enabled.	The Damper position is driven based on Temperaue, IAQ, and CFM. For more information on the actual calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

During Heating:

• • When the space current temperature falls below the Heating Desired Temperature the HeatingLoopOutput is enabled as below.

If System Equipment in Cooling Mode

If System Equipment in Heating Mode

The Damper remains at a minimum from 0% - 50% of the Heating Loop Output, till a maximum Discharge Air Temperature (DAT) is reached, defined by the reheatZoneMaxDischargeTemp tuner (90) Then the Reheat loop output is enabled, based on the DAT set point and actual DAT for the loop output calculation. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

The HeatingLoopOutput is mapped to the Damper position actuator and further to modulating reheat or reheat stages. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation

• • The CO2 and IAQ loops are disabled. (If configured for)
  • The CFM loop is disabled. (If configured for)

During Cooling:

• • When the space current temperature is above the Cooling Desired Temperature the CoolingLoopOutput is enabled as below,

If System Equipment in Cooling Mode

If System Equipment in Heating Mode

The CoolingLoopOutput is mapped to the Damper position actuator for the damper position between the min-max damper position cooling. For more information on the Damper position calculation refer to DAB Terminal Profile- Damper Position Calculation & Operation The CFM loop is enabled  (If configured for) which is mapped to the Damper position actuator for more information on the CFM influence on the operation refer to DAB Terminal Profile- Damper Position Calculation & Operation

The Damper position moves to the minimum position, not allowing further hot air into the room. The Active airflow setpoint will be no higher than the minimum endpoint (minimum Cfm)

• The CO2 and IAQ loops are disabled. (If configured for)

Note: The fan runs wherever the zone is occupied and when the reheat is enabled.

| Sequence of Operation During Emergency Conditioning

When zone limits are violated, and the recorded temperature is within the zone limit plus leeway the conditioning will happen in the direction of zone load.

| Sequence of Operation During Zone Temp Dead

And, When the zone temperature breaches the zone limits, beyond the leeway limits all the following loops are disabled:

• • CoolingLoopOutput
  • HeatingLoopOutput
  • Reheat Stages
  • FanLoopOutput
  • CO2 & IAQ LoopOutput
  • CFM LoopOutput

| Control Mode Summary

Modes &  Operation	Pre-Conditioning	Occupied	AutoAway	Unoccupied	Forced Occupied
Auto	HeatingLoopOutput FanLoopOutput CoolingLoopOutput FanloopOutput CFMLoopOutput	HeatingLoopOutput FanLoopOutput CoolingLoopOutput FanloopOutput CFMLoopOutput CO2LoopOutput IAQLoopOutput	HeatingLoopOutput FanLoopOutput CoolingLoopOutput FanloopOutput	HeatingLoopOutput FanLoopOutput CoolingLoopOutput FanloopOutput	HeatingLoopOutput FanLoopOutput CoolingLoopOutput FanloopOutput
Heat Only	HeatingLoopOutput FanLoopOutput	HeatingLoopOutput FanLoopOutput CO2LoopOutput IAQLoopOutput	HeatingLoopOutput FanLoopOutput	HeatingLoopOutput FanLoopOutput	HeatingLoopOutput FanLoopOutput CO2LoopOutput IAQLoopOutput
Cool Only	CoolingLoopOutput FanLoopOutput CFMLoopOutout	CoolingLoopOutput FanloopOutput CFMLoopOutput CO2LoopOutput IAQLoopOutput	CoolingLoopOutput FanLoopOutput	CoolingLoopOutput FanLoopOutput	CoolingLoopOutput FanLoopOutput CO2LoopOutput IAQLoopOutput
Off	All Loops Deactivated