[Vav22] Variable air volume, internal control
Program block, name / node subtype: [Vav22] Variable air volume, internal control
Library hierarchy: Ventilation and air conditioning equipment
Family: Vav
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Configurator
Program blocks are stored in the library without I/Os. Use the auto-create and auto-connect functions to create I/Os and/or to connect them to the interface blocks, e.g., R_A, CMD_B. Alternatively, take the I/Os from the folder containing the predefined I/Os in the library and/or from the plant and connect them to the interface blocks.
Performs internal control for a VAV.
Internal control (from the point of view of the PXC4/5/7): The VAV control is performed in the PXC4/5/7. It measures the volume flow and modulates a damper position to control the air volume flow.
This type of control is typical for bigger duct sizes (no VAV box for this size) for which no VAV box is available and air volume flow is measured (with AirFlCalc21 or AirFlCalc22) and a normal damper is modulated.
The nominal air volume flow must be set (via analog configuration value).
This program block has the following optional functions:
Option: Air volume flow deviation
An analog calculated value shows the percentage of undersupply (the air volume flow cannot reach the setpoint even if the damper is fully opened).
The air volume flow deviation can be used for fan speed optimization.
Option: Minimum air volume flow
Configuration for a minimal air volume flow (in m3/h) that is maintained.
Name | Description | Type | Alarm / Notification class | Trend / Type | |
|---|---|---|---|---|---|
AirFlCalc | Air volume flow calculation | [AirFlCalc21] Air volume flow calculation, as a function of differential pressure | N/A | N/A | |
Pos | Position | AO: Analog output | No | Yes, 2 | |
AirFlCtr | Air volume flow controller | Ctr: Controller | N/A | N/A | |
AirFlNom | Nominal air volume flow | ACnfVal: Analog configuration value | No | No | |
Name | Description | Type | Alarm / Notification class | Trend / Type | |
|---|---|---|---|---|---|
AirFlMin | Minimum air volume flow | ACnfVal: Analog configuration value | No | Yes, 4 | |
AirFlDvn | Air volume flow deviation | ACalcVal: Analog calculated value | No | No | |