Siemens RDG400 - Manual (Page 22)

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Siemens RDG100…/RDG110…/RDG140.../RDG160… Basic Documentation CE1P3182en
Building Technologies Functions 28 May 2009
4.7.7 Single duct with heating / cooling coil
In single duct applications with heating / cooling coil, the controller controls an
actuator (damper, VAV system, etc.) plus a reheating / cooling water coil.
The output signal for the air flow can be limited to a minimum and maximum value
if required (see section 4.6 "additional features").
The thermostat controls the reheating / cooling water valve either in heating / coo-
ling mode with changeover (automatic or manual), heating only, or cooling only.
Cooling only is factory set (P01=01).
If the room temperature is above the setpoint for cooling, the valve will receive an
OPEN command and the air flow signal starts to rise in order to maintain the room
temperature.
If the room temperature drops below the setpoint for heating, then the valve will
receive an OPEN command.
The diagram below shows the control sequence for continuous PI control in
Comfort mode.
On/off heating / cooling coil Modulating heating / cooling coil
Y
YHC
TR [°C]
SDC
C H
dz
ma
x
mi
n
Y
0%
100%
TR [°C]
XpC
YV
C
Vmin
Vmax
Changeover water
YH
C
ON
OFF
W
SDH
Y
0%
100%
YHC
TR [°C]
XpH
W
XpC
YHC
C H
dz
ma
x
mi
n
Y
0%
100%
TR [°C]
XpC
YV
C
Vmin
Vmax
Changeover water
Y Output signal
TR Room temperature
W Comfort setpoint
H Heating sequence
C Cooling sequence
YV Volume flow rate
XpH Proportional band heating
XpC Proportional band cooling
Vmin Minimum volume output
Vmax Maximum volume output
Note: The diagrams show the PI controller's proportional part only.
Setting the sequence and the control outputs
Refer to sections 4.5 (applications), 4.7.1 (sequences) and 4.7.3 (outputs).
Water coil valve in
cooling mode
Water coil valve in
heating mode
Control sequence