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Siemens RDG100, RDG100T, RDG110, RDG140, RDG160 Basic Documentation CE1P3181en
Building Technologies Functions 28 May 2009
4.7.6 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 changeover sensor input status (see automatic heating
and cooling changeover sensor, section 4.6). This mode is used for the so-called
“Main a
nd secon
dary” application. This is a 4-pipe fan coil unit system with different
capacity 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 factory setting for the heating and cooling changeover sensor (B2 in the
above diagram) is input X2 (P40 = 2)
• 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
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