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Siemens
RDF300… / RDF340... / RDF400… / RDF600… Basic Documentation
CE1P3076.en
Smart Infrastructure
2020-02-21
4.6.3
4-pipe fan coil unit
In 4-pipe applications, the controller controls two 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 selector button if
parameter P01 is set to manual (P01=2).
The heating and cooling output is swapped per the sensor input status (see
automatic heating and cooling changeover sensor), if parameter P01 is set to
changeover (P01=3). This mode is used for “Main and Secondary” application,
which equates to a 4-pipe fan coil unit system with different capacity for heating
and cooling coils. The water circuit is changed to optimize the energy exchange
depending on the season (summer/winter).
T
B1
V2
V1
M1
3
0
7
6D
2
3
T
B2
The diagram below shows the control sequence for on/off (2-position) control.
Heating and cooling mode (P01 = 4 or 3)
T[°C] Room temperature
w
Room temperature setpoint
V1
Control. command “Valve” or “Comp.” Heat
V2
Control. command “Valve” or “Comp.” Cool
SDH Switching differential “Heating”
SDC Switching differential “Cooling”
X
dz
Dead zone
Heating mode with manual selection
(P01=2)
Cooling mode with manual selection
(P1=2)
Heating and cooling
4-pipe application with
manual selection
“Main and Secondary”
application (4-pipe
with changeover)
Control sequence
on/off output
