Siemens RDF302 Documentation

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Siemens RDF302 Basic documentation CE1P3079en
Building Technologies 07 Dec 2011
3.6.4 4-pipe fan coil unit
On 4-pipe applications, the thermostat controls 2 valves in heating and cooling
mode, heating / cooling mode by manual selection, or heating and cooling mode
with changeover. Heating and cooling mode (P01 = 4) is factory-set.
The heating or cooling output can be released via operating mode button if
parameter P01 is set to Manual (P01 = 2).
If parameter P01 is set to changeover (P01 = 3), the heating and cooling output is
swapped according to the input state of the changeover sensor / switch / Modbus
input (see automatic heating and cooling changeover sensor in section 3.5). This
mode is u
sed for the so-called “Main and secondary” application. This is a 4-pipe
fan coil unit system with different capacities of the 2 coils. The water circuit is
changed to optimize the energy exchange depending on the season (summer /
winter):
– Winter: Large coil (V1) for heating, small coil (V2) for cooling
– Summer: Large coil (V1) for cooling, small coil (V2) for heating
T
B1
V2
V1
M1
3181D112
T
B2
Y
1
0
w
w
3181D117
T[°C]
YC
YH
Changeover
YH
YC
V1
V2
Changeover
Note:
This example shows
ON/OFF control;
for modulating con-
trol, connect the
appropriate output
terminals
 The parameter for the heating and cooling changeover sensor (B2 in the above
diagram) must be set to 2 (X1 or X2, P38 or P40)
 The thermostat assumes winter operation when B2 > P37 (factory setting 28 °C)
 The thermostat assumes summer operation when B2 < P36 (factory setting 16 °C)
Heating and cooling
4-pipe application with
manual changeover
"Main and secondary"
application (4-pipe with
changeover)
Notes:

Siemens RDF302 Specifications

General

Brand	Siemens
Model	RDF302
Category	Thermostat
Language	English