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Siemens RDG400 Basic Documentation CE1P3182en
Building Technologies 2015-05-20
4.7.5 Single-duct with electric heater
On single-duct applications with electric heater, the thermostat controls a valve
plus an auxiliary electric heater. Parameter P01 is not available.
The output signal for the air flow can be limited to a minimum and maximum value
if required (see section 4.6 for details).
The air flow starts to rise when the acquired room temperature is above setpoint
plus dead zone.
The electric heater receives an ON command when the acquired room temperature
drops below setpoint (= setpoint for electric heater).
Remote enabling/disabling of the electric heater is possible via input X1, X2, or D1
for overheat protection, tariff regulations, energy savings, etc.
Input X1, X2, or D1 must be commissioned accordingly (parameters P38, P40,
P42). See section 4.9 for details.
In case of insufficient air flow, the thermostat cannot protect the electric heater
against overtemperature. That is why the electric heater must feature a separate
safety device (thermal cutout).
On/Off electric heater Modulating electric heater
Y Output signal
TR Room temperature
W Effective setpoint Comfort
H Heating sequence
C Cooling sequence
YV Volume flow rate
YE Electric heater
XpH Proportional band heating
XpC Proportional band cooling
Vmin Minimum volume output
Vmax Maximum volume output
SDH Switching Differential Heating
The diagrams show the PI controller's proportional part only.
Setting the sequence and the control outputs
Refer to section 4.5, 4.7.1 and 4.7.3 for details.
When the electric heater is switched off, the fan overruns for 60 seconds
(parameter P54) to avoid overtemperature of the electric heater or prevent the
thermal cutout from responding.
Electrical heating,
active in cooling mode
Digital input "Enable
electric heater"
Caution
Sequences
Note:
Fan overrun for
electric heater
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