CET supply air VAV box, pressure sensor, duct area, venturi valve (CetVavSu15)

SOverview

The application function "CET room pressurization supply air VAV box 15, differential pressure sensor, duct area, internal air flow controller, venturi valve" (CetVavSu15) operates a venturi air valve, using both closed loop and open loop control to drive the measured flow to an airflow setpoint (VavSuSpAirFl) that it calculates based on demand signals received for heating, cooling and ventilation. It can control airflow with a settling time of 1 to 2 seconds when applied with the right peripheral devices. It can also be set up for slower operation.

The main output is a modulating output for venturi air valve position (VavSuPos) that is generated by a PID airflow controller in this AF. Functions to support air balancing and venturi air valve calibration are included.

Note
To calculate supply air volume flow, this AF uses a duct areacalculation and input from a differential pressure sensor.

Main features:

Function

The figure below shows BACnet objects associated with this application function. Primary signal flow is summarized as follows:

Basic function: Accept request signal(s) (VavSuSpAflRel and VavSuAflScale) from associated room controller and map it to appropriate airflow setpoint; Pass result through a device mode logic switch prior to outputting as a command to the air flow setpoint object (VavSuSpAirFl); Compare setpoint to airflow in terminal box.

 

Command or request (or related)

Notification of condition or status, or availability

Device mode

Interlock (internal signal, not a BACnet object; see Interlocks section for additional information)

Device mode: The input signal for device mode is a multistate value.

VavSuDevMod supports the following states:

Available status: When the VAV supply damper is available for heating or cooling or ventilation, the respective binary output signal(s) that indicate availability (VavSuAvlH, VavSuAvlC, VavSuAvlVnt) will be "Yes" (available).

For available status to be "Yes", device mode must equal "Control mode" (modulation) and VavSuChovrCnd (Supply air VAV changeover condition) cannot equal "Neither".

Airflow control loop (cascade control)

Airflow controller: The PID airflow controller (VavSuAirFlCtr) compares the airflow volume of the Venturi valve to the current VAV supply airflow setpoint, and modulates VavSuPos as necessary to keep the box flow at setpoint.

ABT 5.x and later:

Airflow setpoint selection: The AF calculates the airflow setpoint for the terminal to satisfy the demand of one of the supported airflow drivers:

The AF maps the demand level in percent to the flow range (min/max values) configured for the active driver. The result is the airflow setpoint for the terminal in physical flow units (ft3/min, m3/h, l/s). Mapping of the demand level to the flow range is as shown in the diagram.

The objects indicating demand level, (VavSuAirFlReq) and the active driver (VavSuAflScale) are inputs to the AF. They are written by other functions. The airflow limits for the terminal are configured here.

Cooling

Heating

Ventilation

Make-up

That setpoint mapping is normal operation. It applies when the device mode (VavSuDevMod) is Control Mode. Special values of device mode alter the setpoint as follows:

  1. Off – Setpoint is 0 and damper is closed
  2. Control Mode – Setpoint follows % demand
  3. Maximum airflow setpoint – Setpoint is maximum for the currently active airflow scale
  4. Minimum airflow setpoint – Setpoint is minimum for the currently active airflow scale
  5. Manual airflow setpoint – Setpoint is value configured for smoke control

Supply Air Flow Limits for Air Terminals - Configuration

The Supply Air Flow serves multiple functions: heating, cooling, ventilation, and pressurization. The following section explains how to configure each supply terminal for different use cases.

Cooling

Heating

Ventilation

Single CV (Constant Volume) Supply Terminal

Min = Max = 0 (or minimum flow value needed for the coil to cool the room)

Min = Max = 0 (or minimum flow value needed for the coil to heat the room)

Min = 0

Max ≥ The largest value configured in Ventilation AF

Single VAV (Variable Air Volume) Supply Terminal (no fume hood)

Min = 0 (or minimum flow value needed for the coil to cool the room)

Max = Value from box schedule

Min = 0 (or minimum flow value needed for the coil to heat the room)

Max = Min (if sequence does not vary flow to heat)
If sequence does vary flow to heat: Max = Value from box schedule

Min = 0

Max Ventilation ≥ Largest value configured in Ventilation AF

Single VAV Supply Terminal (fume hood)

Min = 0 (or minimum flow value needed for the coil to cool the room)

Max = Value from box schedule

Min = 0 (or minimum flow value needed for the coil to heat the room)
Max = Min (if sequence does not vary flow to heat)
If sequence does vary flow to heat: Max = Value from box schedule

Min Ventilation = 0
Max Ventilation ≥ Largest value configured in Ventilation AF or value needed to balance maximum fume hood flow

Check the project specification to see if the various terminals are to be sequenced differently from each other: if they respond to different needs. If no difference is specified, follow the next table's instruction. If the flow limits are set the same for each terminal, then they run at equal flows.

Cooling

Heating

Ventilation

Multiple Supply Terminals (same size, same function)

Min = 0 (or minimum flow value needed for the coil to cool the room)

Max = Value from box schedule (specified per terminal)

Min = 0 (or minimum flow value needed for the coil to heat the room)

Max = Min (if sequence does not vary flow to heat)
If sequence does vary flow to heat: Max = Value from box schedule

Min = 0

Max ≥ The largest of configured ventilation levels for the room and the supply flow needed to balance fume hoods, divided by the number of supply terminals

Check the project specification to see if the various terminals are to be sequenced differently from each other: if they respond to different needs. If the supply terminals are different sizes but have the same function, follow the next table's instruction.

Cooling

Heating

Ventilation

Multiple Supply Terminals (different sizes, same function)

Min = 0 (or minimum flow value needed for the coil to cool the room)

Max = Value from box schedule (specified per terminal)

Min = 0 (or minimum flow value needed for the coil to heat the room)

Max = Min (if sequence does not vary flow to heat)
If sequence does vary flow to heat: Max = Value from box schedule

Min = 0

Max ≥
1. The largest value of the terminal being configured or
2. The value needed to balance maximum fume hood flow of the terminal being configured

In the case of multiple supply terminals with different functions, the following tables provide an example of how to configure one CV (Constant Volume) Terminal serving a chilled beam, and one VAV (Variable Air Volume) Terminal without cooling.

Flow through the CV Terminal does not vary to heat or cool.
Flow is always set by ventilation or support for coil (minimum heat or minimum cooling) unless reducing it is the only way to maintain room pressurization.

Flow through the VAV Terminal may vary for heating, cooling, and ventilation, or to balance fume hood flow.

Cooling

Heating

Ventilation

Multiple Supply Terminals (different functions)
CV Terminal

Min = Max = 0 (or minimum flow value needed for the coil to cool the room)

Min = Max = 0 (or minimum flow value needed for the coil to heat the room)

Min = Max = 0 (or value needed to support a heating or cooling coil)

Multiple Supply Terminals (different function)
VAV Terminal

Min = 0 (or minimum flow value needed for the coil to cool the room)

Max = Value from box schedule (specified per terminal)

Min = 0 (or minimum flow value needed for the coil to heat the room)

Max = Min (if sequence does not vary flow to heat)
If sequence does vary flow to heat: Max = Value from box schedule

Min = 0

Max ≥
1. The largest value of the terminal being configured or
2. The value needed to balance maximum fume hood flow of the terminal being configured

ABT 4.x and earlier

Airflow setpoint selection: The AF calculates the airflow setpoint for the terminal to satisfy the demand of one of the supported airflow drivers:

The AF maps the demand level in percent to the flow range (min/max values) configured for the active driver. The result is the airflow setpoint for the terminal in physical flow units (ft3/min, m3/h, l/s). Mapping of the demand level to the flow range is as shown in the diagram.

Cooling

Heating

Ventilation

Make-up

The objects indicating demand level, (VavSuAirFlReq) and the active driver (VavSuAflScale) are inputs to the AF. They are written by other functions. The airflow limits for the terminal are configured here.

That setpoint mapping is normal operation. It applies when the device mode (VavSuDevMod) is Control Mode. Special values of device mode alter the setpoint as follows:

  1. Off – Setpoint is 0 and damper is closed
  2. Control Mode – Setpoint follows % demand
  3. Maximum airflow setpoint – Setpoint is maximum for the currently active airflow scale
  4. Minimum airflow setpoint – Setpoint is minimum for the currently active airflow scale
  5. Manual airflow setpoint – Setpoint is value configured for smoke control

Airflow control with Venturi air valve: The AF has three ways to control airflow with the Venturi valve: PID control, a linear characterization curve, and the linear characterization curve combined with PID control. The user selects the loop control by setting the configuration property (AirFlCtlMod) and by setting up the data table for the characterization curve.

AirFlCtlMod

Characterization Curve

Setpoint

Control action

closed loop

configured

> AirVMinCtlClb

combined

closed loop

configured

< AirVMinCltClb

curve only

closed loop

not configured

any

PID only

closed loop

configured

any

curve only

closed loop

not configured

any

fail mode

open loop

configured

> AirVMinCtlClb

curve only

open loop

configured

< AirVMinCltClb

curve only

open loop

not configured

> AirVMinCtlClb

curve only (output to actuator will be zero)

open loop

not configured

< AirVMinCltClb

curve only (output to actuator will be zero)

open loop

configured

any

curve only

open loop

not configured

any

fail mode

--

calibrating

--

curve

 

PID control: The PID control will be used when the closed loop configuration is selected and the characterization table has not been configured.

The PID controller is fixed in the modulating mode. Two-position operation, if needed, is achieved by providing a 2-position setpoint signal.

Linear characterization curve: Open loop control, by the 15 point linear characterization curve will be used to position the venturi when open loop control is selected.

Open loop control is also active if the user selects closed loop control and the airflow setpoint equates to an velocity setpoint of less than the minimum control velocity (AirVMinCtlClb). The default setting is 1.778 m/s (350 fpm).

The x and y points for the linear characterization curve can be entered manually or they can be automatically entered by running the venturi calibration.

Linear characterization curve with PID: Combined control applies when configured closed loop control is selected and the characterization curve is configured, and the airflow setpoint, the duct velocity is above the minimum velocity for control.

When the setpoint changes quickly, and both calculation paths respond, the system is likely to overshoot. To reduce this tendency, the setpoint signal to the PID controller is delayed to arrive in synch with change in airflow caused by the open loop actuator movement. For most effective operation, users should adjust the delay (TiConSpAflRel) to correspond to the stroke time of the actuator.

Flow sensor failure without characterization curve: If the airflow sensor object is invalid (not including over range) then, the flow control damper position will be set based on the setting of the configuration extension AirFlFailMod.

While the sensor is failed, PID operation is suspended. When status of the sensor is valid again, the PID resumes operation.

When the AI is unreliable, airflow calculations continue, however, airflow value might not change because the value of the AI stops updating. The AF also sets a binary value object indicating normal or faulty state of the airflow data.

Flow sensor failure with characterization curve: If the controller detects flow sensor failure (not including over range) it switches to control by the characterization curve alone.

Sensor calibration: While the airflow sensor is in active calibration, the acitve flow control is suspended; the output does not change and the integrator does not increment. This applies to closed loop control. When the status returns to normal, there may be a bump in output due to proportional action.

Open loop control (with characterization curve) continues to operate, and may move the actuator during calibration.

Airflow sensing: The AF calculates volumetric airflow from a measured differential pressure value and supports other functions associated with the airflow sensor. It supports manual operations associated with air balancing and works with the APS and other pressure sensors, that includes an Auto-zero function. The AF does not include calculations or data to zero a sensor.

When the velocity in the duct is low (below AirVMinCtlClb) the controller uses the value from the characterization curve, rather than the flow measurement to command the airflow object.

Low sensor value: Configuration settings specify a switch-on point and hysteresis value in units of pressure.

In Venturi applications, this feature has no effect because the cut out velocity for the sensor is much lower than the value where the controller switches to the calibration curve.

If the AI object representing the DP sensor indicates a failure and the characterization curve is configured, the controller switches to the Venturi air valve for flow data. The calculated value object, representing airflow shows the value from the characterization curve, and the reliability of that object does not indicate a problem. Other values derived from the flow value also indicate reliable data.

Duct area calculation: The duct area is calculated based on configuration data.

Airflow coefficient: The airflow coefficient is configuration data (VavSuFlCoef). Users may enter the coefficient directly or enter their own, independent airflow readings and have the AF calculate and set the flow coefficient.

Air balancing: Balancing functions are not connected with the air pressurization functions.The air balancing functions are:

Balancing functions are not connected with room pressurization functions. It is expected that the room may lose pressurization when the balancer performs balancing steps.

Interlocks

Room automation interlocks are internal signals that coordinate interaction between HVAC devices. They are not visible in ABT Site or web interface, but parameters associated with them are. See comment column for hints on parameters that affect interlock functionality.

Signal

Type

Dir.

Description

Comment

AirFlCReq

Boolean

In

Airflow cooling request
▶ Initiates airflow (damper opens) to satisfy airflow support request from cooling coil.

 

AirFlHReq

Boolean

In

Airflow heating request
▶ Initiates airflow (damper opens) to satisfy airflow support request from heating coil.

 

AirFlHldH

Boolean

In

Airflow hold for heating
▶ Interlock signal from electric heating coil indicating the coil needs equipment protection airflow support. The damper is prevented from closing for a period of time.

 

AirFlHldC

Boolean

In

Airflow hold for cooling
▶ Interlock signal from cooling coil indicating the coil needs equipment protection airflow support. The damper is prevented from closing for a period of time.

 

AirFlSta

Boolean

Out

Airflow status
▶ Interlock signal that keeps the coil locked at equipment protection priority (PrPrio = 5) unless the supply damper provides air flow.

See Configuration section for parameters named "...AirFlSta"

 

Supply chain interface: There are four demand output signals for air.

Airflow deviation signal: The supply airflow deviation (VavSuAirFlDvn) signal (in percent) is used for fan speed (static pressure) reset strategies at the air handling unit. It is obtained by measuring the airflow from the supply duct and comparing it to the airflow setpoint.

VavSuAirFlDvn = VavSuSpAflRel minus VavSuAirFlRel

VavSuAirFlDvn will equal 0 in case of invalid condition(s).

Saturation signal: The saturation signal VavSuAflStrtn is a binary object that is True ("Starved") when the airflow control loop cannot get enough air to reach setpoint for a time exceeding a built-in time delay.

Note
VavSuAflStrtn is always off if parameter EnStrtnCal = 0 (No). This allows the user to exclude a particular terminal from the saturation pressure reset system.

In order for Saturation Signal to be True:
1. The Enable Saturation Calibration parameter must be set to Yes (EnStrtnCal=Yes)
2. The output of the VAV controller must be greater than the saturation level (VavEhAirFlCtr>StrtnLvl)
3. The air flow error, which is the setpoint minus airflow value, must be greater than the air flow error limit (AirFlEr>AirFlErLm)

Saturation Signal can only be True when all three parts are satisfied for the duration of DlyOnStrtn.

AHU changeover condition signal: The multistate VAV supply changeover condition input signal (VavSuChovrCnd) comes from the room coordinating function (RCoo). It indicates the current heating / cooling available status for central AHU. If the supply air system does not include a changeover function, do not connect this value to a source of data. Configure the value to the normal AHU operation state. The default is Cooling.

Four states are supported:

  1. Neither
  2. Heating
  3. Cooling
  4. Neutral

"Neutral" means that heating and cooling PID controllers are both enabled and that the system is providing air that is not hot or cold.

Configuration

Objects

Description

Object

Type

Default value

Supply air VAV balancing state
▶ Indicates the state of progress of the balancing process for this VAV box; is written by the controller in response to the user-entered balance command; persists through a power cycle.

1:Initial
2:Balancing
3:Balanced

VavSuBalSta

MCnfVal

1:Initial

Supply air VAV balancing mode
▶ Air flow value set by the air balancer person to select the air flow setpoint value used when the balancing state = balancing.

1:Maximum cooling
2:Maximum heating
3:Maximum ventilation
4:Minimum cooling
5:Minimum heating
6:Minimum ventilation
7:Smoke

VavSuBalMod

MCnfVal

1:Maximum cooling

Supply air VAV air volume flow at hood
▶ Externally measured air flow value, entered by air balancer, used to calculate flow coefficient.

VavSuAirFlHood

ACnfVal

100 [m3/h]
58.9 [ft3/min]
27.78 [l/s]

Supply air VAV recorded balancing mode
▶ Stored value for balance report; balance mode value at time of record trigger.

Enumeration see VavSuBalMod

VavSuBalModRec

MCnfVal

1:Maximum cooling

Supply air VAV recorded air volume flow at hood
▶ Stored value for balance report; hood flow value at time of record trigger.

VavSuAflHodRec

ACnfVal

0 [m3/h]
0.0 [ft3/min]
0.00 [l/s]

Supply air VAV recorded flow coefficient
▶ Stored value for balance report; flow coefficient value after calibrate trigger.

VavSuFlCoefRec

ACnfVal

0.000

Supply air VAV initial flow coefficient
▶ The value of flow coefficient as found prior to balancing; this value is recorded when the user-entered Balancing Command is set to Balancing.

VavSuFlCoefIni

ACnfVal

0.000

Supply air VAV recorded air volume flow
▶ Stored value, for balance report, of the current, calculated air flow.

VavSuAirFlRec

ACnfVal

0 [m3/h]
0.0 [ft3/min]
0.00 [l/s]

Supply air VAV recorded position
▶ Stored value of the damper position at the time of the record trigger.

VavSuPosRec

ACnfVal

0 [%]

Supply air VAV duct area
▶ Duct cross-sectional area, user-entered or calculated by controller using the duct shape, dimension A and dimension B values.

0…1 [m2], 0.0…10.76 [ft2]

VavSuDuctArea

ACnfVal

0.05 [m2]
0.54 [ft2]

Supply air VAV duct shape
▶ Duct cross-sectional shape; Data entry by user triggers area calculation by controller; Direct entry uses user-entered area, not controller calculation.

1:Rectangular
2:Round
3:Flat oval
4:Direct entry

VavSuDuctShape

MCnfVal

2:Round

Supply air VAV dimension A
▶ For rectangular duct: Width; for round duct: Diameter; for flat oval duct: Total width (major dimension) ; for Direct entry: Not used.

0…100 [cm], 0.0…39.4 [in]

VavSuDmsnA

ACnfVal

20 [cm]
7.9 [in]

Supply air VAV dimension B
▶ For rectangular duct: Height; for round duct: Not used; for flat oval duct: Height (minor dimension); for Direct entry: Not used.

0…100 [cm], 0.0…39.4 [in]

VavSuDmsnB

ACnfVal

20 [cm]
7.9 [in]

Supply air VAV flow coefficient
▶ The value used to calibrate span of air flow measurement; the value of calc flow coefficient is written to this object upon the Calibrate command.

VavSuFlCoef

ACnfVal

0.780

Supply air VAV smoke control air volume flow setpoint
▶ Air flow setpoint if VavSuDevMod=5. Air flow used in balancing if VavSuBalMod = 7; balancer can use this as a manual air flow setting.

VavSuSpAflSmk

ACnfVal

50 [m3/h]
29.4 [ft3/min]
13.89 [l/s]

Supply air VAV maximum air volume flow for cooling
▶ Maximum airflow setpoint when in cooling mode. Typically this is related to the size of the terminal. The airflow used for balancing when the Supply air VAV balancing mode = 1.

VavSuAirFlMaxC

ACnfVal

100 [m3/h]
58.9 [ft3/min]
27.78 [l/s]

Supply air VAV minimum air volume flow for cooling
▶ Minimum airflow setpoint when in cooling mode. Minimum cooling flow should be set to zero (0) in most installations without a cooling coil in the terminal. If the terminal has a cooling coil, minimum cooling flow should be set high enough for effective heat transfer. The airflow used for balancing when the Supply air VAV balancing mode = 4.

VavSuAirFlMinC

ACnfVal

50 [m3/h]
29.4 [ft3/min]
13.89 [l/s]

Supply air VAV maximum air volume flow for heating
▶ Maximum airflow setpoint when in heating mode. Often set at a level needed to transfer heat from the reheat coil to the room at maximum heating demand. The airflow used for balancing when the Supply air VAV balancing mode = 2.

VavSuAirFlMaxH

ACnfVal

100 [m3/h]
58.9 [ft3/min]
27.78 [l/s]

Supply air VAV minimum air volume flow for heating
▶ Minimum airflow setpoint when in heating mode. Often set at a level needed to transfer heat from the reheat coil to the room at low load and can be set lower if primary air is warm. The airflow used for balancing when the Supply air VAV balancing mode = 5.

VavSuAirFlMinH

ACnfVal

50 [m3/h]
29.4 [ft3/min]
13.89 [l/s]

Supply air VAV maximum air volume flow for ventilation
▶ Maximum ventilation airflow setpoint for indoor air quality (IAQ) controller and for Rapid Ventilation. Sometimes this can be equal to cooling maximum, sometimes less. This allows ventilation and cooling capacities to be specified separately. The airflow used for balancing when the Supply air VAV balancing mode = 3.

VavSuAflMaxVnt

ACnfVal

100 [m3/h]
58.9 [ft3/min]
27.78 [l/s]

Supply air VAV minimum air volume flow for ventilation
▶ Only used during balancing. The air flow used for balancing when the Supply air VAV balancing mode = 6.
The setting for minimum ventilation can be found in the ventilation AF at the room level.

VavSuAflMinVnt

ACnfVal

0 [m3/h]
0.0 [ft3/min]
0.00 [l/s]

Parameters

Description

Parameter

Default value

Failure mode for air volume flow sensor
▶ Defines how the terminal responds if the air volume flow sensor fails.

1:Hold supply air
2:Open supply air
3:Close supply air

▶Also defines how the terminal responds if loss of network communication occurs.
1. Hold: Setpoint does not change
2. Close: Setpoint is set to the minimum flow of the mode the terminal was in during failure
3. Open: Setpoint is set to the maximum flow of the mode the terminal was in during failure

AirFlFailMod

1:Hold supply air

Switch-on point for differential pressure
▶ The differential pressure sensor signal value must be above this value or else zero is used.

SwiOnPtDiffP

0.2 [Pa]
0.001 [inWC]

Hysteresis for differential pressure
▶ Amount below SwiOnPtDiffP below which the pressure value used by the controller will be zero.

HysDiffP

0.1 [Pa]
0.000 [inWC]

Time constant for air volume flow
▶ The time constant for the attenuation filter on the air volume flow sensor.
Increase the value to help stabilize fluctuating air volume flow sensor values, leaving at 0 disables the filter.

TiConAirFl

0 [s]

Switch delay for tracking method to air volume flow
▶ The airflow tracking signal that is sent to the room will automatically switch from setpoint to airflow when: Absolute Value (Relative Setpoint – Relative Air Flow) > SwiTolTckMthd, for a time longer than SwiTolTckMthd.
SETTING TOLERANCE LEVEL (SwiTolTckMthd) TO 100% WILL NOT ALWAYS PREVENT TRACKING FROM SWITCHING FROM SETPOINT TO AIRFLOW.

SwiDlyTckMthd

60 [s]

Switch tolerance for tracking method to air volume flow
▶ The airflow tracking signal that is sent to the room will automatically switch from setpoint to airflow when: Absolute Value (Relative Setpoint – Relative Air Flow) > SwiTolTckMthd, for a time longer than SwiTolTckMthd.
SETTING TOLERANCE LEVEL (SwiTolTckMthd) TO 100% WILL NOT ALWAYS PREVENT TRACKING FROM SWITCHING FROM SETPOINT TO AIRFLOW.

SwiTolTckMthd

5.0 [%]

Nominal air volume flow
▶ Optional. Maximum airflow capacity of the VAV box. Set no larger than 1.2 times the greater of the values of maximum airflow for ventilation or heating or cooling.

AirFlNom

0 [m3/h]
0.0 [ft3/min]
0.00 [l/s]

Control mode for air volume flow

0:Open-loop control
1:Closed-loop control

AirFlCtlMod

1:Closed-loop control

Minimum air velocity for control and venturi calibration
▶ During venturi calibration, the calibration process will stop when the duct velocity is below AirVMinCtlClb.
During operation, if operating in closed loop control and the venturi has been calibrated, control will switch to open loop control when the air flow setpoint correlates to a duct velocity setpoint less than AirVMinCtlClb.

AirVMinCtlClb

1.778 [m/s]
350 [ft/min]

Time constant for relative air volume flow setpoint
▶ Rate limiting feature – the amount of time to increase the relative setpoint to the VAV air flow controller from 0% to 100% or decrease from 100% to 0%.
This is used when using the linear characterization curve with PID control. When the setpoint changes quickly, and both calculation paths respond, the system is likely to overshoot. To reduce this tendency, the relative setpoint signal to the PID controller is delayed to arrive approximately in synch with change in air flow caused by the open loop actuator movement.
Typically is set to match the actuator run time. Set to 0 if using PID only control.

TiConSpAflRel

2 [s]

Enable deviation calculation
▶ Enables the calculation of the deviation value (airflow setpoint minus airflow value) to be available for AHU fan static setpoint reset. See also section Air flow deviation signal.

0:No
1:Yes

EnDvnCal

1:Yes

Enable saturation calculation
▶ Enables the saturation signal calculation logic for AHU fan static pressure reset. See also section Saturation signal.

Set to "Yes" to include this VAV in the AHU static fan pressure reset logic.
Set to "No" to exclude undesired VAV from the AHU static fan pressure reset logic. An example of an undesired VAV would be a VAV that is part of a rogue zone.

0:No
1:Yes

EnStrtnCal

1:Yes

Saturation level
▶ The minimum VAV controller output before the saturation logic would send a starved signal (if other conditions are true; see Saturation signal section). In a calibrated venturi valve, the VAV controller output represents the venturi position deviation from the venturi calibration table. The saturation level is used for AHU static fan pressure reset to maximize energy efficiency while maintaining the pressure independence of the venturi valve.

A higher value prioritizes energy efficiency while a lower value prevents insufficient airflow.

StrtnLvl

90 [%]

Air volume flow error limit
▶ The maximum allowable tolerance below airflow setpoint before the saturation logic would send a starved signal (if other conditions are true; see Saturation signal section). The airflow error limit is used to allow deviation below the airflow setpoint when the saturation level is exceeded. When set to 0, ignores calculation for AirFlErLm.

AirFlErLm

0 [%]

Switch-on delay saturation
▶ The time after the saturation conditions are met that the saturation signal to the AHU changes from False to True.

DlyOnStrtn

60 [s]

Switch-on point for air flow demand
▶ Airflow value (in percent of the largest configured max airflow) that defines the airflow demand switch-on point. The airflow setpoint VavSuSpAirFl must equal or exceed this value before the terminal box begins to open.

SwiOnAirFlDmd

4 [%]

Hysteresis for air flow demand
▶ Hysteresis offset used to determine the airflow demand cutoff value. SwiOnAirFlDmd minus HysAirFlDmd = the airflow value that VavSuSpAirFl needs to fall below before the damper closes.

HysAirFlDmd

2 [%]

Switch-on point for air volume flow state
▶ The airflow above which the VavSuAirFlTck signal switches from the supply air flow setpoint to the actual supply airflow (assuming SpSelVavEx is set to True).

SwiOnAirFlSta

10 [%]

Hysteresis for air volume flow state
▶ The airflow below SwiOnAirFlSta, below which the VavSuAirFlTck signal switches from the supply air flow to the supply air flow setpoint (assuming SpSelVavEx is set to True).

HysAirFlSta

5 [%]

Pressure unit
▶ Defined by selected engineering unit – do not change.

PUnit

[Pa]
[inWC]

Air volume flow unit
▶ Defined by selected engineering unit – do not change.

AirFlUnit

[m3/h]
[ft3/min]
[l/s]

Air velocity unit
▶ Defined by selected engineering unit - do not change.

AirVUnit

[m/s]
[ft/min]

Interface

Interface

Description

Type

Ref.

Owned by

VavSuPos

Supply air VAV position

AO

◉

Room segment / Field device

VavSuDiffP

Supply air VAV differential pressure

AI

◉

Room segment / Field device

VavSuAirVEff

Supply air VAV effective air velocity

ACalcVal

●

-

VavSuSpAirFl

Supply air VAV setpoint for air volume flow

APrcVal

●

-

TrndVavSuSpAfl

Trend for supply air VAV setpoint for air volume flow

FtrSel

●

-

VavSuSpAflRel

Supply air VAV setpoint for relative air volume flow

ACalcVal

●

-

VavSuAirFl

Supply air VAV air volume flow

ACalcVal

●

-

TrndVavSuAirFl

Trend for supply air VAV air volume flow

FtrSel

●

-

VavSuAirFlRel

Supply air VAV relative air volume flow

ACalcVal

●

-

VavSuAirFlDvn

Supply air VAV air volume flow deviation

ACalcVal

●

-

VavSuAflStrtn

Supply air VAV air volume flow saturation

0:Satisfied
1:Starved

BCalcVal

●

-

VavSuDevMod

Supply air VAV device mode

1:Off
2:Control mode
3:Maximum air volume flow
4:Minimum air volume flow
5:Smoke control air volume flow setpoint

MPrcVal

●

-

VavSuAirFlCtr

Supply air VAV air flow controller

Controller

●

-

VavSuAirFlReq

Supply air VAV air volume flow request

ACalcVal

●

-

VavSuAflScale

Supply air VAV air volume flow scale

1:Heating
2:Cooling
3:Ventilation
4:Make-up air

McalcVal

●

-

VavSuRqdC

Supply air VAV required for cooling

0:Off
1:On

BCalcVal

●

-

VavSuRqdH

Supply air VAV required for heating

0:Off
1:On

BCalcVal

●

-

VavSuAvlC

Supply air VAV available for cooling

0:No
1:Yes

BCalcVal

●

-

VavSuAvlH

Supply air VAV available for heating

0:No
1:Yes

BCalcVal

●

-

VavSuAvlVnt

Supply air VAV available for ventilation

0:No
1:Yes

BCalcVal

●

-

VavSuChovrCnd

Supply air VAV changeover condition

1:Neither
2:Heating
3:Cooling
4:Neutral

MPrcVal

●

-

VavSuAirDmd

Supply air VAV air demand for plant mode

1:Off
2:Protection
3:Economy
4:Pre-Comfort
5:Comfort
6:Warm-up
7:Cool down
8:Room low temperature protection
9:Not used
10:Free cooling
11:Night cooling
12:Ventilation
13:Not used
14:Air volume flow off
15:Smoke extraction positive pressure
16:Smoke extraction negative pressure
17:Purge

MCalcVal

●

-

VavSuCDmd

Supply air VAV cooling demand

ACalcVal

●

-

VavSuHDmd

Supply air VAV heating demand

ACalcVal

●

-

VavSuVntDmd

Supply air VAV ventilation demand

ACalcVal

●

-

VavSuAirFlTck

Supply air VAV air volume flow tracking

ACalcVal

●

-

VavTckMthd

VAV tracking method

1:Setpoint
2:Air volume flow

McalcVal

●

-

VntrSuClbCmd

Supply air venturi valve calibration command

1:Ready
2:Calibrate
3:Apply
4:Cancel

MTrgVal

●

-

VntrSuClbSta

Supply air venturi valve calibration state

1:Initial
2:Failed calibration
3:Calibrated

MCalcVal

●

-

VavSuFlCoefCal

Supply air VAV calculated flow coefficient

ACalcVal

●

-

VavSuBalCmd

Supply air VAV balancing command

1:Ready
2:Balancing
3:Calibrate
4:Record
5:Balanced

MTrgVal

●

-

CdnMsgCol

Collection of condensation message

ColView

●

-

 

CdnMsgRs

Result of condensation message

0:Normal
1:Alert

BCalcVal

●

-

CdnMsg

Condensation message

Enumeration see CdnMsgRs

BCalcVal

◉

CcgChw11 / HCcg2Pipe11 / HCcg4Pipe11 / HCcg4Pipe13

CclCdnMsg

Cooling coil condensation message

Enumeration see CdnMsgRs

BCalcVal

◉

CclChw13

VavSuSplyAir

Supply air VAV supply chain for air

GrpMbr

●

-

VavSuBalSta

Supply air VAV balancing state

1:Initial
2:Balancing
3:Balanced

MCnfVal

●

-

VavSuBalMod

Supply air VAV balancing mode

1:Maximum cooling
2:Maximum heating
3:Maximum ventilation
4:Minimum cooling
5:Minimum heating
6:Minimum ventilation
7:Smoke

MCnfVal

●

-

VavSuAirFlHood

Supply air VAV air volume flow at hood

ACnfVal

●

-

VavSuBalModRec

Supply air VAV recorded balancing mode

1:Maximum cooling
2:Maximum heating
3:Maximum ventilation
4:Minimum cooling
5:Minimum heating
6:Minimum ventilation
7:Smoke

MCnfVal

●

-

VavSuAflHodRec

Supply air VAV recorded air volume flow at hood

ACnfVal

●

-

VavSuFlCoefRec

Supply air VAV recorded flow coefficient

ACnfVal

●

-

VavSuFlCoefIni

Supply air VAV initial flow coefficient

ACnfVal

●

-

VavSuAirFlRec

Supply air VAV recorded air volume flow

ACnfVal

●

-

VavSuPosRec

Supply air VAV recorded position

ACnfVal

●

-

VavSuDuctArea

Supply air VAV duct area

ACnfVal

●

-

VavSuDuctShape

Supply air VAV duct shape

1:Rectangular
2:Round
3:Flat oval
4:Direct entry

MCnfVal

●

-

VavSuDmsnA

Supply air VAV dimension A

ACnfVal

●

-

VavSuDmsnB

Supply air VAV dimension B

ACnfVal

●

-

VavSuFlCoef

Supply air VAV flow coefficient

ACnfVal

●

-

VavSuSpAflSmk

Supply air VAV smoke control air volume flow setpoint

ACnfVal

●

-

VavSuAirFlMaxC

Supply air VAV maximum air volume flow for cooling

ACnfVal

●

-

VavSuAirFlMinC

Supply air VAV minimum air volume flow for cooling

ACnfVal

●

-

VavSuAirFlMaxH

Supply air VAV maximum air volume flow for heating

ACnfVal

●

-

VavSuAirFlMinH

Supply air VAV minimum air volume flow for heating

ACnfVal

●

-

VavSuAflMaxVnt

Supply air VAV maximum air volume flow for ventilation

ACnfVal

●

-

VavSuAflMinVnt

Supply air VAV minimum air volume flow for ventilation

ACnfVal

●

-

Engineering and commissioning

Check for correct actuator installation. Actuator mis-wiring or improper installation is a major cause of common problems.

The relative airflow (VavSuAirFlRel) is normalized as a percentage (0 - 100%) of VavSuAirFl based on the nominal (rated) value for the box air flow (AirFlNom).