VAV ventilation control, pressure dependent (VavVntCtl12)

Overview

The application function "VAV ventilation control 12, pressure-dependent control" (VavVntCtl12) collaborates / is used only with pressure dependent VAV supply air terminal boxes for ventilation and/or room air quality control.

Function

Different modes are available for ventilation control; the behavior is selectable by parameter.

Ventilation mode
The ventilation mode can be set per room operating mode to:

Off
Minimum (Fixed damper position)
Dcv (Demand controlled ventilation) ¹⁾
Dcv & Min (Demand controlled ventilation with a minimum damper position limit) ¹⁾

¹⁾ Air quality sensor required in the room.

The table shows factory default settings for min vent and air quality parameters:

Plant mode	Ventilation mode	Sp air quality [ppm]	Damper min position [%]
1 Off	Off
2 Protection*	Off	1500	50
3 Economy*	Off	1500	50
4 Pre-Comfort*	Dcv	1100	50
5 Comfort*	Min & Dcv	900	50
6 Warm-up	Off
7 Cool down	Off
8 Room low temperature protection	Off
9 <not used>
10 Free cooling	Depends on ROpMod	Depends on ROpMod	Depends on ROpMod
11 Night cooling	Off
12 Rapid ventilation	s/a Comfort	s/a Comfort	s/a Comfort
13 <not used>
14 Emergency off	Off
15 Max.supply air vol.flow only (positive pressure)	Off
16 Max.extract air vol.flow only (negative pressure)	Off
17 Purge Max.supply and extract air vol. flow	Off

*For these modes the parameters can be individually adjusted.

Periodic air flush
Parameters are available to configure periodic cycling of ventilation air flow. Ventilation can be enabled for minimum air flow at regular intervals, for the length of time in TiOnDutyCyc. See figure.

The length of the duty cycle off interval can be configured for each operating mode (DutyCycCmf, DutyCycPcf, DutyCycEco, DutyCycPrt). A duty cycle of 0min (default) means the feature is disabled.

Note
If the room temperature is measured with an extract air temperature sensor, air must flow to ensure the effective room temperature is measured correctly. In this case, periodic air flush can be used to provide air flow at regular intervals.

Exception handling
For air quality control, the ventilation mode must be set to Dcv or Min & Dcv, VavSuAvlVnt must be Yes and the air quality sensor must be Valid. If the sensor is failed or absent, then the ventilation mode cannot be Dcv or Min & Dcv; in this case VavSuVntReq is set to Min.

Configuration

Objects

Description	Object	Type	Default value
Setpoint room air quality for comfort	SpAQualRCmf	ACnfVal	900 [ppm]
Setpoint room air quality for pre-comfort	SpAQualRPcf	ACnfVal	1100 [ppm]
Setpoint room air quality for economy	SpAQualREco	ACnfVal	1500 [ppm]
Setpoint room air quality for protection	SpAQualRPrt	ACnfVal	1500 [ppm]

Parameters

Description	Parameter	Default value
Comfort configuration 1:Off 2:Minimum ventilation 3:Demand-controled ventilation 4:Minimum ventilation & Demand-controlled ventilation	CmfCnf	4:Minimum ventilation & Demand-controlled ventilation
Pre-Comfort configuration Enumeration see CmfCnf	PcfCnf	3:Demand-controled ventilation
Economy configuration Enumeration see CmfCnf	EcoCnf	2:Minimum ventilation
Protection configuration Enumeration see CmfCnf	PrtCnf	2:Minimum ventilation
Minimum damper position for comfort ▶ When CmfCnf is set to 4:Minimum ventilation & Demand-controlled ventilation and IAQ sensor configured and Valid, damper position during Comfort will equal the DmpPosMinCmf setting or the demand-controlled ventilation position, whichever is larger.	DmpPosMinCmf	50 [%]
Minimum damper position for pre-comfort	DmpPosMinPcf	50 [%]
Minimum damper position for economy	DmpPosMinEco	50 [%]
Minimum damper position for protection	DmpPosMinPrt	50 [%]
Duty cycling in comfort	DutyCycCmf	0 [min]
Duty cycling in pre-comfort	DutyCycPcf	0 [min]
Duty cycling in economy	DutyCycEco	0 [min]
Duty cycling in protection	DutyCycPrt	0 [min]
Switch-on time duty cycling ▶ If periodic cycling of ventilation air flow is desired, TiOnDutyCyc defines the length of "on" time for the ventilation air flow. Periodic cycling requires duty cycle parameter(s) to be set to non zero value (DutyCycCmf, DutyCycPcf, DutyCycEco, DutyCycPrt).	TiOnDutyCyc	6 [min]

Interface

Interface	Description	Type	Ref.	Owned by
PrSpVnt	Present ventilation setpoint	APrcVal	●	-
VntCtr	Ventilation controller	Controller	●	-
RCtl	Room control	GrpMaster	◉	Room
SpAQualRCmf	Setpoint room air quality for comfort	ACnfVal	●	-
SpAQualRPcf	Setpoint room air quality for pre-comfort	ACnfVal	●	-
SpAQualREco	Setpoint room air quality for economy	ACnfVal	●	-
SpAQualRPrt	Setpoint room air quality for protection	ACnfVal	●	-