Technical data

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Siemens RDG100KN Basic documentation CE1P3191en
Building Technologies Functions 22 Jun 2010
3.6.7 4-pipe fan coil unit with electric heater
On 4-pipe applications with electric heater, the thermostat controls 2 valves in
heating and cooling mode by manual selection, heating and cooling mode with
automatic changeover, heating only, or cooling only plus an auxiliary electric
heater. Heating and cooling is factory-set (P01 = 4).
The electric heater is used as an additional heat source when the heating energy
controlled by the valve is insufficient.
The electric heater receives an ON command when the temperature is below
“setpoint” minus “1/2 "dead zone" minus "setpoint differential" (= setpoint for
electric heater).
Remote enabling / disabling of the electric heater is possible via input X1, X2, or
D1 for tariff regulations, energy saving, etc.
Input X1, X2, or D1 must be commissioned accordingly (parameters P38, P40,
P42). See section 3.9 “Multifunctional input”.
The ele
ctric heater can also be enabled / disabled via bus.
If the bus input is used, then the function must NOT be assigned to a local input
X1, X2 or D1.
An electric heater must always be protected by a safety limit thermostat!
The heating or cooling output can be released via operating mode button if
parameter P01 is set to Manual (P01 = 2).
See section 3.6.6.
The diag
rams below show the control sequence for 2-position control.
Heating mode with manual selection (P01 = 2) Cooling mode with manual selection P01 = 2)
Y
1
0
w
3181D125a
T[°C]
½ SDH ½ SDH
Y1
½ SDH ½ SDH
W
D
YE
Y
½ SDC
1
0
½ SDC
w
3181D126a
T[°C]
Y2
Heating and cooling mode (P01 = 4)
T[°C] Room temperature
w Room temperature setpoint
YE Control command “El heater"
Y1 Control command “Valve” (H)
Y2 Control command “Valve” (C)
SDH Switching differential “Heating” (P30)
SDC Switching differential “Cooling” (P31)
X
dz
Dead zone (P33)
Y
½ SDC
1
0
½ SDC
w
3181D113a
T[°C]
Y2
½ SDH
½ SDH
Y1
½
x
dz
½ x
dz
½ SDH ½ SDH
W
D
YE
w
D
Setpoint differential (P34)
Heating and cooling with
auxiliary heater
Electric heating in
heating mode
Digital input “Enable
electric heater”
KNX
R
Enable electric heater
Caution
4-pipe application with
manual changeover
“Main and secondary”
application
ON/OFF control