Technical data

3.6.3 2-pipe fan coil unit
On 2-pipe applications, the thermostat controls a valve in heating / cooling mode
with changeover (automatically or manually), heating only, or cooling only. Cooling
only is factory-set (P01 = 1).
ON/OFF control
The diagrams below show the control sequence for 2-position control.
Heating mode Cooling mode
½ SDH
1
0
½ SDH
w
Y
3076D01
T[°C]
Y1
Y
½ SDC
1
0
½ SDC
w
3076D02
T[°C]
Y1
T[°C] Room temperature
SDH Switching differential "Heating" (P30)
w Room temperature setpoint
SDC Switching differential "Cooling" (P31)
Y1 Control command "Valve" or "Compressor"
Modulating control: 3-position
The diagrams below show the control sequence for modulating PI control.
Heating mode Cooling mode
XpH
100
0
w
Y [%]
3076D03
T[°C]
Y1
XpC
Y [%]
100
0
w
3076D04
T[°C]
Y1
T[°C] Room temperature
XpH Proportional band "Heating" (P30)
w Room temperature setpoint
XpC Proportional band "Cooling" (P31)
Y1 Control command "Valve"
• The diagrams only show the PI thermostat’s proportional part.
• For the fan sequence see section 3.8.
Setting the sequence and the control outputs
Refer to sections 3.4 "Applications", 3.6.1 "Sequences", and 3.7 "Outputs".
Control sequence
ON/OFF output
Control sequence
modulating output
Note:
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Siemens RDF301, RDF301.50..., RDF600KN Basic documentation CE1P3171en
Building Technologies Functions 2014-05-23