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CE1N3547en_c
Siemens
2018-10-10
Building Technologies
Operating modes
Volume flow control (VAV or CAV)
Variable air volume (VAV) control: the operating point is determined by the setpoint value
and the Vmin / Vmax settings (cf. diagram below). Constant air volume (CAV) control is
achieved by sending a constant setpoint or by setting Vmin = Vmax.
1 Setpoint range
2 Actual value range
3 Controlled area
Position control
The VAV compact controllers can be operated as damper actuators, i.e. using the 0..100%
setpoint as position damper setpoint, by setting the operating mode parameter to “POS”.
Commissioning and parameterization
Parameterization of the VAV application
VAV application parameters are set by the OEM over the PPS2 interface (using ACS931 or
AST20). Some of them can be adjusted during commissioning, operation, or maintenance
and are accessible over a bus connection alternatively.
Parameter
Range
Description
Factory settings
Operating mode
VAV / POS
VAV: setpoint = volume flow 0…100%
POS: setpoint = damper position 0...100%
VAV
Opening direction
CW (R) / CCW (L) Opening direction of air damper
CW (R)
Adaptive positioning Off / On
Adaption of actual (if mech. limited) opening range
to position feedback 0...100%
Off = No adaption / On = Pos. adaption
Off
Vmin
-20…100%
Minimum air volume flow, rel. to Vnom
0 %
Vmax
20…120%
Maximum air volume flow, rel. to Vnom
100 %
Vnom
0…60‘000 m
3
/h
Nominal air volume flow
100 m
3
/h
Box coefficient (Vn) 1…3.16
VAV box characteristic value, defined by the OEM 1.00
Altitude /
Elevation asl.
0…5000m
in 500m steps
Correction factor for diff. pressure sensor (select
n*500m value closest to local altitude)
500 m
Vmax [%]
Vmin [%]
3
