2-Pipe Fan Coil Unit With Radiator Or Floor Heating - Siemens RDG100KN Basic Documentation

Heating or cooling with
radiator or floor heating
Radiator, active in
cooling mode
Radiator in heating mode
Floor heating
On/Off control
Modulating control: 3-position, PWM or DC 0...10 V
Note
Setting sequence and control outputs
Note
52 / 132
Siemens
Building Technologies
3.6.5

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 tempera-
ture 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 tempera-
ture is below the setpoint. The fan coil unit is used as an additional heat source
when the heating 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 34.
The diagrams below show the control sequence for On/Off control.
Heating mode
YHC
Y YR
w
D
1
w
0
½ SDR
½ SDH ½ SDH
T[°C] Room temperature
W Room temperature setpoint
YHC Control command "Valve" or "Compressor"
YR Control command "Radiator"
The diagrams below show the control sequence for modulating PI control.
Heating mode
Y [%] YHC YR
w
D
100
0
XpH
XpR
T[°C] Room temperature
W Room temperature setpoint
YHC Control command "Valve"
YR Control command "Radiator"
The diagr ams only show the PI thermostat's proportional part.
See 3.4, 3.6.1, and 3.7.
Parameter P78 (RDG160KN SW version
when using a PICV. See 3.5.
RDG100KN, RDG160KN, RDG165KN Basic Documentation
Cooling mode
Y
1
0
T[°C]
½ SDR
½ SDR
SDH Switching differential "Heating" (P30)
SDC Switching differential "Cooling" (P31)
SDR Switching differential "Radiator" (P32)
X Dead zone (P33)
dz
w Setpoint differential (P34)
D
Cooling mode
Y [%]
100
T[°C]
0
w
XpH Proportional band "Heating" (P30)
XpC Proportional band "Cooling" (P31)
XpR Proportional band "Radiator" (P32)
X
dz
w
D
2.04) sets the heating flow limitation
YR
YHC
x
dz
w
T[°C]
½ SDC ½ SDC
½ SDR
YR
YHC
x
dz
XpR w
XpC
Dead zone (P33)
Setpoint differential (P34)
T[°C]
CE1P3191en
2018-07-03