Technical data

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Siemens RDG400KN Basic documentation CE1P3192en
Building Technologies Functions 20 Jul 2010
3.6.7 Single-duct with heating / cooling coil
On single-duct applications with heating / cooling coil, the thermostat controls an
actuator (air damper, VAV system, etc.) plus a heating / cooling water coil.
The output signal for the air flow can be limited to a minimum and maximum value
if required (see section 3.5 "Additional features").
The thermost
at 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).
The air flow starts to rise depending on the acquired room temperature, the current
supply air temperature (if available) and the setpoint.
If the room temperature is above the setpoint for cooling ((w)), the valve will receive
an OPEN command and the air flow signal starts to rise to maintain the room
temperature setpoint.
If the room temperature drops below the setpoint for heating (w), then the valve will
receive an OPEN command.
The diagrams below show the control sequence for modulating PI control in
Comfort mode.
2-position heating / cooling coil
Modulating heating / cooling coil
Y
YHC
TR [°C]
SDC
C
H
dz
max
min
Y
0%
100%
TR [°C]
XpC
YV
C
H
Vmin
Vmax
XpH
Changeover water
YHC
ON
OFF
w
SDH
Changeover air
(w)
Y
0%
100%
YHC
TR [°C]
XpH
w
XpC
YHC
C
H
dz
max
min
Y
0%
100%
TR [°C]
XpC
YV
C
H
Vmin
Vmax
XpH
Changeover water
Changeover air
(w)
Y Output signal
TR Room temperature
w Comfort setpoint if changeover water = Heating
(w) Comfort setpoint if changeover water = Cooling
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
Water coil valve in
cooling mode
Water coil valve in
heating mode
Control sequence