Assortment / System Description

Central applications
Automation station for HVAC supply and demand signals and manual control for lighting and blinds
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Neither changeover condition
Heating and cooling in the VAV application is blocked and the setpoints are set
to a start setpoint for heating and cooling.
● High setpoint for supply air temperate (SpHiTSu) = Start value for cooling
SttValC
● Low setpoint for supply air temperature (SpLoTSu) = Start value heating
SttValH
Conclusion for the room: Neither heating nor cooling, the volume flow controller
for room temperature is not enabled.
Changeover condition neutral
Heating and cooling in the VAV application is enabled and the setpoints are set
to a start setpoint for heating and cooling.
● High setpoint for supply air temperate (SpHiTSu) = Start value for cooling
SttValC
● Low setpoint for supply air temperature (SpLoTSu) = Start value heating
SttValH
The following variants are available on the DXR2 to optimize fan speed on air
handling units with speed-controlled fans:
● Speed optimization via damper positions
The 10 largest supply air and extract air damper positions are acquired and
the average calculated. The resulting value is used for fan speed
optimization of the AHU.
● Speed optimization via air volume deviation.
The deviation signals from the supply air VAV controllers are acquired from
the room segments. The air volume flow deviation is calculated as:
((air flow setpoint - measured air flow) / nominal air flow)) x 100[%]
The 10 largest deviations are evaluated and the average is used to optimize
the fan stage.
The number of deviations is counted between 5...20% for monitoring.
● Speed optimization via setpoint evaluation of volume flow. It is used is
supply air damper positions and measured air flows are not known. The
setpoints of the supply air and extract VAV boxes is added up and the AHU
fan stage is used as of this value for optimized air flow.
Relief function monitoring becomes active as soon as air supply is activated. It
calculates air demand for the AHU to ensure sufficient control stability of static
pressure in the AHU. A relief command is outputted to the VAV controller in the
group if room demand is too low; it reacts by increasing the air flow setpoint to
increase air demand.
Description Name Default value
Configurable min. number of air demand requests
required for operational stability of the central AHU.
1...50
AirDmdMax 10
Hysteresis for number of maximum air demand plant
mode
1...5
HysAirDmdMax 2
VAV evaluation for
AirOptiControl
Relief function