4-Pipe Fan Coil Unit - Siemens RDG100 Basic Documentation

Heating and cooling
4-pipe application with
manual changeover
"Main and secondary"
application (4-pipe with
changeover)
V2
T
B2
V1
Notes
Siemens
Building Technologies
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 and secondary" 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
Y
1
0
M1
T
B1
 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)
RDG100, RDG100T, RDG110, RDG140, RDG160
Functions
Changeover
YH
YC
w
w
YH
V1
YC
V2
Note:
T[°C]
This example shows
on/off control;
for modulating con-
trol, connect the
appropriate output
Changeover
terminals.
Basic Documentation
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CE1P3181en
14 Dec 2011