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Siemens
RDU340… Basic Documentation
CE1P3078en
Building Technologies
Functions
2014-11-03
4.5 Additional
features
The air or water temperature acquired by the changeover sensor (QAH11.1) is
used to change over from heating to cooling mode and vice-versa. When the water
temperature is above 28 °C (parameter P37), the controller changes over to
heating mode, and to cooling mode when below 16 °C (parameter P36). If the
water temperature is between the 2 changeover points immediately after power up,
the controller starts in heating mode. The water temperature is acquired at 30-
second intervals and the operating state is updated accordingly.
M Operating mode
Cooling mode
T
w
Air or water temperature
Heating mode
The QAH11.1 cable temperature sensor for automatic heating/cooling changeover
can be replaced by an external switch for manual, remote changeover:
Contact open
à
heating mode
Contact closed
à
cooling mode
The sensor or switch can be connected to the input terminal of X2 (factory setting)
or X1 depending on the commissioning of inputs X1 and X2. See also section
“Multifunctional input”.
The controller acquires the room temperature via built-in sensor, external room
temperature sensor (QAA32), or external return air temperature sensor (QAH11.1)
connected to multifunctional input X1 or X2.
Inputs X1 or X2 need to be commissioned accordingly. See section 4.8 “Multi-
functional input”.
Dewpoint monitoring is essential to prevent condensation on the chilled ceiling and
help avoid associated damage to the building. This is an optional function and is
provided in case the controller is used for a chilled ceiling application.
A dewpoint sensor with a voltage-free contact is connected to multifunctional input
X1 or X2. If there is condensation, the cooling valve is fully closed until no more
condensation is detected and the cooling output is disabled temporarily. The
condensation symbol
is displayed during temporary override.
Input X1 or X2 must be commissioned accordingly.
See section “4.8 Multifunctional input”.
If the key lock function is enabled by parameter P14, then pressing 7 seconds on
the operating mode button
, the keypad will be locked or unlocked respectively.
If “Auto lock” is configured, then the controller will automatically lock the keypad
after 30 seconds of the last adjustment.
Automatic H/C
changeover
Remote heating/
cooling changeover
External/return
temperature sensor
Dewpoint monitoring
Key lock
Min / Max air flow
