CET supply air VAV box, pressure sensor, duct area (CetVavSu12)

Overview

The application function "CET room pressurization supply air VAV box 12, differential pressure sensor, duct area, internal air flow controller, air damper" (CetVavSu12) operates a damper, using closed 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 damper position (VavSuPos) that is generated by a PID airflow controller in this AF. Functions to support air balancing are included.

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

Main features:

VAV supply damper modulation for temperature control and ventilation purposes
Airflow setpoint calculation
Airflow calculation
Airflow coefficient calculation (air balancing logic)
Interlocks (box coils)
Supply chain interface

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:

Off
Control mode
Max.air vol.flow
Min.air vol.flow
Smoke ctrl.air flow setp.

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 terminal box 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:

Heating
Cooling
Ventilation
Make-up

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:

Off – Setpoint is 0 and damper is closed
Control Mode – Setpoint follows % demand
Maximum airflow setpoint – Setpoint is maximum for the currently active airflow scale
Minimum airflow setpoint – Setpoint is minimum for the currently active airflow scale
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:

Heating
Cooling
Ventilation
Make-up


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:

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

Feedback loop: A feedback controller drives the AO object for the damper. The feedback loop uses relative values for flow and setpoint. Both physical values are converted to a percentage of a scaling value for use in the PID loop. These relative values for flow and setpoint are written to calculated value objects. (This is different from the scaling used to express the demand for heating, cooling or ventilation.) The scaling value used is the highest flow setpoint expected in the programmed control sequence. It is the largest of the various maximum flow limits configured for the terminal:

cooling maximum flow
heating maximum flow
ventilation maximum flow
nominal flow

Flow sensor failure: 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.

If AirFlFailMod is set to Hold, the damper will stay in the current position.
If AirFlFailMod is set to Open, the damper position will be set to 100%.
If AirFlFailMod is set to Close, the damper position will be set to 0%.

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.

Network communication loss: If network communication loss occurs, the flow setpoint will be set based on the setting of the configuration extension AirFlFailMod.

If AirFlFailMod is set to Hold, the flow setpoint will stay in the current position.
If AirFlFailMod is set to Open, the flow setpoint will be set to the maximum flow of the mode the terminal was in during failure.
If AirFlFailMod is set to Close, the flow setpoint will be set to the minimum flow of the mode the terminal was in during failure.

When the network communication is lost, the flow control loop continues to operate with the setpoint selected from above.

Sensor calibration: While the airflow sensor is in active calibration, the closed loop flow control is suspended; the output does not change. Calibration only occurs during periods of steady state control, not when the flow setpoint is changing.

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.

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

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:

Set flow setpoint according to selected balancing mode.
Calculate duct area
Calculate flow coefficient.
Apply airflow coefficient.
Restore automatic operation.
Record data for balancing report.

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.

VavSuCDmd - Supply air VAV cooling demand
When device mode is in control, VavSuCDmd is the percentage value of the cooling request from the room (otherwise it is 0).
VavSuHDmd - Supply air VAV heating demand
When device mode is in control, VavSuHDmd is the percentage value of the heating request from the room (otherwise it is 0).
VavSuVntDmd - Supply air VAV ventilation demand
When device mode is in control, VavSuVntDmd is the percentage value of the ventilation request from the room (otherwise it is 0).
VavSuAirDmd - Supply air VAV air demand for plant mode
VavSuAirDmd is a multistate value that equals PltOpMod (VavSuSpAirFl must be greater than the switch-on point for airflow demand, SwiOnAirFlDmd). If PltOpMod is "Emergency Off" or "Smoke Negative Pres.", VavSuAirDmd will equal PltOpMod regardless of VavSuSpAirFl value.

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:

Neither
Heating
Cooling
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 ▶ Airflow value set by the air balancer person to select the airflow 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 airflow 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
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
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 airflow measurement; the value of calc flow coefficient is written to this object upon the Calibrate command. 0…2	VavSuFlCoef	ACnfVal	0.78
Supply air VAV smoke control air volume flow setpoint ▶ Airflow setpoint if VavSuDevMod=5. Airflow used in balancing if VavSuBalMod = 7; balancer can use this as a manual airflow 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]
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 Airflow 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 damper position before the saturation logic would send a starved signal (if other conditions are true; see Saturation signal section).The saturation level is used for AHU static fan pressure reset to maximize energy efficiency by reducing airflow resistance in the duct system due to the damper. 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 airflow 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 airflow to the supply airflow 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]

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	●	-
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 damper 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 airflow or the highest of heating max, cooling max, or vent max. (AirFlNom).