4.7.7Single duct with heating / cooling coil
Water coil valve in cooling mode
Water coil valve in heating mode
Control sequence
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
Y | XpC |
| |
100% | C | ||
| |||
|
| ||
Vmax |
| max | |
|
| ||
Vmin | YV |
| |
min |
| ||
|
| ||
0% |
|
|
TR [°C]
Changeover water |
Modulating heating / cooling coil
Y | XpC |
| |
100% | C | ||
| |||
|
| ||
Vmax |
| max | |
|
| ||
Vmin | YV |
| |
min |
| ||
|
| ||
0% |
|
|
TR [°C]
Changeover water
Y | SDH | SDC |
|
H | C | ||
ON |
|
|
|
| YHC | HCY |
|
|
|
| |
OFF | W |
|
|
| dz |
| |
|
| TR [°C] | |
|
|
|
Y
H XpH
100%
0%W
dz
XpC C
YHC
TR [°C]
Y | Output signal |
TR | Room temperature |
WComfort 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).
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Siemens | RDG100…/RDG110…/RDG140.../RDG160… Basic Documentation | CE1P3182en |
Building Technologies | Functions | 28 May 2009 |
