2-Pipe Fan Coil Unit - Siemens RDF302/VB Manual

ON/OFF control
Control sequence
ON/OFF output
Modulating control: 3-position
Control sequence
modulating output
Note:
Setting the sequence and the control outputs
24 / 62
Siemens
Smart Infrastructure
3.6.2

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).
The diagrams below show the control sequence for 2-position control.
Heating mode
Y
V1
1
w
0
½ SDH ½ SDH
T[° C] Room temperature
w Room temperature setpoint
V1 Control command "Valve" or "Compressor"
The diagrams below show the control sequence for modulating PI control.
Heating mode
Y [%]
V1
100
0
w
XpH
T[° C] Room temperature
w Room temperature setpoint
V1 Control command "Valve"
The diagrams only show the PI thermostat's proportional part.
Refer to sections 3.4 "Applications", 3.6.1 "Sequences", and 3.7 "Outputs".
RDF302 Basic documentation
Cooling mode
Y
1
T[° C]
0
½ SDC
SDH Switching differential "Heating" (P30)
SDC Switching differential "Cooling" (P31)
Cooling mode
Y [%]
100
T[° C]
0
XpH Proportional band "Heating" (P30)
XpC Proportional band "Cooling" (P31)
V1
w
T[° C]
½ SDC
V1
T[° C]
w
XpC
CE1P3079en
2022-06-17