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Siemens
RDF300… / RDF340... / RDF400… / RDF600… Basic Documentation
CE1P3076.en
Smart Infrastructure
2020-02-21
4.6.1
2-pipe fan coil unit
In 2-pipe applications, the controller controls a valve in heating/cooling mode with
changeover (automatic or manual), heating only mode, or cooling only mode.
Cooling only is factory set (P01=1).
The diagram below shows the control sequence for on/off (2-position) control.
Heating mode
Cooling mode
T[°C]
Room temperature
SDH
Switching differential “Heating”
w
Room temperature setpoint
SDC
Switching differential “Cooling”
V1
Control command “Valve” or “Compressor”
The diagram below shows the control sequence for continuous PI control.
Heating mode
Cooling mode
T[°C]
Room temperature
XpH
Proportional band “Heating”
w
Room temperature setpoint
XpC
Proportional band “Cooling”
V1
Control command “Valve”
·
The diagrams only show the PI thermostat’s proportional part.
·
For the fan sequence see section 4.8.
On/off output
Heating or cooling
Control sequence
on/off output
Control sequence
modulating output
Notes:
