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| Description of Equipment

The SmartNode is a highly versatile input/output (IO) controller. Many applications can be set up out of the box with minimal configuration options. The SmartNode can also be used for more custom sequences outside its typical terminal application profiles. 

The SmartNode VAV Terminal Profiles (Series Fan with reheat, Parallel Fan reheat, No Fan with Reheat) are zone-level controllers that control a typical VAV box in a building.

Based on whether the system level equipment AHU or RTU is in cooling mode or Heating mode the damper and reheat operations enable to provide the optimum results for the zone based on the zone load.

The SmartNode VAV Terminal Profiles (Series Fan with reheat, Parallel Fan reheat, No Fan with Reheat) allow the choice of dampers, reheat based on the equipment used, and the zone priority which equates to the importance multiplier in guideline 36.

Quick Summary
Damper Control Reset based on Space Temperature and/or  CO2 and/or  VOC and /or CFM & mode of operation.
Reheat Control Reset based on Space Temperature & mode of operation at the system level
Fan Control

Reset based on Reheat

| Schematics

VAV No Fan with Electric Reheat

 

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VAV No Fan with Modulating Reheat

 

VAV_No_Fan.png

 

VAV Series Fan with Electric Reheat

 

VAV_Series_Electric_RH.png

VAV Series Fan with Modulating Reheat

 

VAV_Series_Modulating_RH.png

VAV Parallel Fan with Electric Reheat

 

VAV_Parallel_Electric_RH.png

VAV Parallel Fan with Modulating Reheat

 

 

| Control System Object List

 Object Name Type Input/Output Type
Heating Desired Temp User Intent NA
Cooling Desired Temp User Intent NA
Current Temp Input OWI Sensor
Humidity Input OWI Sensor
Occupancy Mode

Input

OWI Sensor
Damper Actuator Output SmartNode Analog Out
Reheat Stage 1 Output SmartNode Relay
Reheat Stage 2 Output SmartNode Relay
Modulating Reheat Output SmartNode Analog Out
Zone Priority Input User Intent/ Configuration Setup
Damper Size & Shape  Input User Intent/ Configuration Setup
Discharge Airflow Temperature Input SmartNode Thermistor
Supply Airflow Temperature Input SmartNode Thermistor
Minimum Damper Position Cooling Input User Intent/ Configuration Setup
Maximum Damper Position Cooling Input User Intent/ Configuration Setup
Minimum Damper Position Heating Input User Intent/ Configuration Setup
Maximum Damper Position Heating Input User Intent/ Configuration Setup
Minimum CFM Cooling Input User Intent/ Configuration Setup
Maximum CFM Cooling Input User Intent/ Configuration Setup
Minimum CFM Reheat Input User Intent/ Configuration Setup
Maximum CFM Reheat Input User Intent/ Configuration Setup
Maximum Damper Heating Input User Intent/ Configuration Setup

 

| Sequence of Operation

The sequence of operation is completely driven based on Occupancy modeSpace 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 is scheduled for occupancy, 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.

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.

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

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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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)
  • After 50% of the Heating Loop Output, the Reheat loop output is enabled, based on the DAT set point and actual DAT for the loop output calculation.
  • When the space CO2 & IAQ levels are above the thresholds the Heating Loop Output above 50% factored CO2/ IAQ loop Outputs drive the damper actuator for damper position.
  • When the CFM-based control is enabled, the Heating Loop Output above 50% factored, A CFM Loop Output, the result of active CFM set point (Result of minimum CFM reheating & Max CFM reheating), and measured CFM drive the damper position.

For more information on the Damper position calculation refer to VAV Terminal Profile- Damper Position Calculation & Operation

  • The HeatingLoopOutput is mapped to the Damper position actuator.
  • When the space CO2 & IAQ levels are above the thresholds the Heating Loop Output factored CO2/ IAQ loop Outputs drive the damper actuator for damper position.
  • When the CFM-based control is enabled, Heating Loop Output factored CFM Loop Output, the result of minimum CFM reheating and actual measured CFM, drives the damper position.

For more information on the Damper position calculation refer to VAV Terminal Profile- Damper Position Calculation & Operation

 

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.
  • When the space CO2 & IAQ levels are above the thresholds the Cooling Loop Output factored CO2/ IAQ loop Outputs drive the damper actuator for damper position.
  • When the CFM-based control is enabled, the Cooling Loop Output is factored, CFM Loop Output, the result of active CFM set point (Result of min CFM cooling & Max CFM cooling), and measured CFM drive the damper position.v

 

For more information on the Damper position calculation refer to VAV Terminal Profile- Damper Position Calculation & Operation

  • The Damper position moves to the minimum position, not allowing further hot air into the room.
  • When the space CO2 & IAQ levels are above the thresholds the Cooling Loop Output above factored CO2/ IAQ loop Outputs drive the damper actuator for damper position.
  • When the CFM-based control is enabled, Cooling Loop Output factored CFM Loop Output, the result of minimum CFM reheating and actual measured CFM, drives the damper position.

For more information on the Damper position calculation refer to VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 VAV 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 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

 

Note: FanLoopOutput/ Fan is applicable only for the VAV terminal profiles with series or parallel fans, and not applicable for the VAV terminal profile with no fan.

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