Assortment / System Description

VAV application
Parallel supply air VAV or extract air VAV
18
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18.4.1 External volume air flow control
A differential pressure sensor is typically connected to the VAV actuator for an
application with external volume flow control. Which in turns also implements
volume flow control. In this case, the application in the DXR2 controls only the
room temperature and forwards the setpoint for volume flow control to the VAV
actuator.
The present damper position is determined in all cases by DXR2 and provided
to the central function for optimizing the supply air fan.
18.4.2 Internal volume flow control
A differential pressure sensor is typically connected to the DXR2 for an
application with internal volume flow control. It can be implemented using the
integrated pressure sensor on the DXR2 or an analog sensor. DXR2 then also
operate volume flow control in addition to temperature control.
The present damper position is determined in all cases by DXR2 and provided
to the central function for optimizing the supply air fan.
18.5 Parallel supply air VAV or extract air VAV
A maximum of one room can be configured on each DXR2. The room can
consist of a maximum of one supply air and extract air VAV. You must create a
multisegment application with multiple DXR2 automation stations if you need
to use multiple VAV for supply or extract air. Any combination of supply air and
extract air VAV can be created with DXR2. The VAV can even have various sizes
and nominal air volume flows.
The standardized room control with controller signals 0…100% always controls
all connected VAV actuators for supply and extract air as per their nominal
volume flow and provide the correct amount of volume flow..
Room control attempts to compensate for a loss of a VAV actuator by using
operational VAV to provide the missing volume flow.
18.6 Outputs
At the VAV outputs, KNX PL-Link VAV actuators, analog VAV actuators, analog
damper actuators (with supplemental differential pressure sensor) or 3-position
damper actuators (with supplemental differential pressure sensor) via Triac
outputs.
18.7 Switch-off delay
The switch off of a fan is delayed for a specific period on applications that have
electric heating coils/reheaters. This cools down the electric heating
coils/reheater with circulating air. The switch-on/switch-off time can be
configured.
Description Name Default value
Switch-off delay holding signal for air volume flow
heating
DlyOffAflHldH 30 [s]