Additional Functions - Siemens RDF302 Documentation

Heating / cooling
changeover via
Modbus
Heating/cooling
changeover
Automatic heating /
cooling changeover via
changeover sensor
Changeover switch
Manual heating /
cooling changeover
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Siemens
Building Technologies
3.5

Additional functions

The heating / cooling changeover information can be received via Modbus. This is
only possible if the control sequence is set to automatic heating / cooling
changeover (parameter P01 = 3) and no local input X1, X2 is assigned with this
function.
In the absence of the required information (e.g. due to problems with data
communication, power failure, etc.), the thermostat operates in the last valid room
operating mode (heating or cooling).
If a cable temperature sensor (QAH11.1 + ARG86.3) is connected to X1 / X2, and
parameter P38 / P40 is =2, the water temperature acquired by the changeover
sensor is used to change over from heating to cooling mode, or vice versa.
 When the water temperature is above 28 °C (adjustable via parameter P37),
the thermostat changes over to heating mode.
It stays in heating mode until the temperature falls below 16°C (adjustable
viaparameter P36)
 When the water temperature is below 16 °C (P36), the thermostat changes
over to cooling mode.
It stays in cooling mode until the temperature rises above 28°C (P37).
 If the water temperature is between the 2 changeover points immediately after
power-up (inside the hysteresis), the thermostat starts in previous mode.
The water temperature is acquired at 30-second intervals and the operating state is
updated accordingly.
M
T
P36
P37
M Operating mode
T Water temperature
w
The QAH11.1 cable temperature sensor for automatic heating / cooling changeover
can be replaced by an external switch for manual, remote changeover:
T °C
The sensor or switch can be connected to input terminal X2 or X1, depending on
the commissioning of the inputs (P38, P40).
See also section 3.9 "Multifunctional input".
 Manual heating / cooling changeover means selection via changeover button on
the thermostat by repeatedly pushing the button until the required mode is
shown on the display (automatic changeover is done via an external sensor /
switch connected to X1, X2, or D1)
 If manual heating / cooling changeover is commissioned (P01 = 2), then heating
/ cooling mode cannot be changed via changeover sensor / switch; it will remain
in the last mode as selected locally via button.
RDF302 Basic documentation
Functions
[°C]
w
Cooling mode
Heating mode
X2 X2
T
M M
QAH11.1
Contact open
 heating mode
Contact closed
3076Z03
 cooling mode
07 Dec 20111
CE1P3079en