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Siemens RDG100, RDG100T, RDG110, RDG140, RDG160 Basic Documentation CE1P3181en
Building Technologies Functions 28 May 2009
4.7.4 2-pipe fan coil unit with electrical heater
On 2-pipe applications with electrical heater, the thermostat controls a valve in
heating / cooling mode with changeover, heating only, or cooling only plus an
auxiliary electrical heater.
Cooling only is factory set (P01=1) with enabled electrical heater (P13).
In cooling mode, the valve receives an OPEN command if the acquired tempera-
ture is above the setpoint.
The electrical heater receives an ON command if the acquired room temperature
drops below “setpoint” minus “dead zone” (= setpoint for electrical heater) while the
electrical heater is enabled (parameter P13 = on).
Note: “Setpoint for electrical heater” is limited by parameter “Maximum heating
setpoint” (P10).
In heating mode, the valve receives an OPEN command if the acquired tempera-
ture is below the setpoint. The electrical heater is used as an additional heating
source when the heating energy controlled by the valve is insufficient.
The electrical heater receives an ON command, if the temperature is below
“setpoint” minus “setpoint differential” (= setpoint for electrical heater).
The electrical heater is active in heating mode only and the control output for the
valve is permanently disabled when manual changeover is selected (P01=2).
Remote enabling / disabling of the electrical heater is possible via input X1, X2 or
D1 for tariff regulations, energy savings, etc.
Input X1, X2, or D1 must be commissioned accordingly (parameters P38, P40,
P42). See section 4.10 “Multifunctional input”.
An electri
cal
heater must always be protected by a safety thermostat!
ON/OFF control
The diagram below shows the control sequence for 2-position.
Heating mode
(automatic changeover = heating or heating only)
Cooling mode
(man. / auto. changeover = cooling or cooling only)
Y
½ SDH
1
0
½ SDH
w
3076D06
T[°C]
Y1
½ SDH
½ SDH
YE
w
D
Y
½ SDC
1
0
½ SDC
w
3076D05
T[°C]
Y1
½ SDH
½ SDH
YE
x
dz
Heating mode with manual changeover (P01=2)
(manual changeover = heating)
T[°C] Room temperature
W Room temperature setpoint
Y1 Control command “Valve” or “Compressor”
YE Control command “Electrical heater”
SDH Switching differential “Heating” (P30)
SDC Switching differential “Cooling” (P31)
X
dz
Dead zone (P33)
½ SDH
1
0
½ SDH
w
Y
3076D07
T[°C]
YE
w
D
Setpoint differential (P34)
Heating or cooling with
auxiliary heater
Electrical heating,
active in cooling mode
Electrical heating in
heating mode
Electrical heating and
manual changeover
Digital input “Enable
electrical heater”
Caution
Control sequence
on/off output
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