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Siemens
RDG100.., RDG110.., RDG160T.. Basic Documentation
CE1P3181en
Building Technologies
Functions
2015-07-29
4.7.5
2-pipe fan coil unit with radiator or floor heating
On 2-pipe applications with radiator, the thermostat controls a valve in heating/cooling
mode with changeover, heating only, or cooling only plus a radiator valve. Cooling only
is factory-set (P01=1).
In cooling mode, the valve receives an
OPEN
command if the acquired temperature is
above the setpoint.
The radiator receives an
ON
command if the acquired room temperature drops below
"setpoint" minus "dead zone" (= "setpoint for radiator").
In heating mode, the radiator receives an
OPEN
command if the acquired temperature
is below the setpoint. The fan coil unit is used as an additional heat source when the
heat energy controlled by the radiator is insufficient.
The fan coil unit receives an
ON
command if the temperature is below "setpoint"
minus "setpoint differential" (= setpoint for fan coil unit).
The radiator sequence can also be used for floor heating.
The "Floor heating limitation function" is described on page 21.
The diagrams below show the control sequence for 2-position control.
Heating mode
Cooling mode
T[°C] Room temperature
SDH Switching differential "Heating" (P30)
W
Room
temperature
setpoint
SDC Switching differential "Cooling" (P31)
YHC Control command "Valve" or "Compressor"
X
dz
Dead zone (P33)
YR Control command "Radiator"
w
D
Setpoint differential (P34)
Modulating control: 3-position, PWM or DC 0…10 V
The diagrams below show the control sequence for modulating PI control.
Heating mode
Cooling mode
T[°C] Room temperature
XpH Proportional band "Heating" (P30)
W
Room
temperature
setpoint
XpC Proportional band "Cooling" (P31)
YHC Control command "Valve"
X
dz
Dead zone (P33)
YR Control command "Radiator"
w
D
Setpoint differential (P34)
The diagrams only show the PI controller’s proportional part.
Heating or cooling with
radiator or floor heating
Radiator, active in
cooling mode
Radiator in heating mode
Floor heating
On/Off control
Note