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Siemens
RXB (KNX) application library
FNC Description of functions for FC-10, FC-11, FC-12 CM110385en_05
Building Technologies
Control sequences
28 Feb 2009
For test purposes, the radiator valve actuator can be overridden via the following
communication objects:
Heating surface output override (Input communication object)
Flags
R W K T U
Type Receive
timeout
Value
0 1 1 0 0 8.010
DPT_Percent_V16
no
00...100% 0 = 0%
+100 = +100%
+32767 = invalid
Before the radiator valve actuator can be overridden, “Test” mode must be activated via
the communication object
Application mode
(see page 128).
8.5.5
Downdraft compensation
This function is only active in
Comfort
mode.
In situations where (owing to large internal heat gains) there is no heating demand from
the room despite a low outdoor temperature (supplied via the bus), large window
surfaces can impair indoor comfort (through radiated cold and the downward flow of
cold air).
A radiator located under the window can be used to “brake” the downward flow of cold
air and compensate for cold radiation.
To achieve this, the radiator is switched on whenever the outdoor temperature drops
below a predefined value (the
Outdoor temp. 0% valve position
).
The maximum heating output (set under
Max. Valve Position
) is reached at the "coldest
outdoor temperature" (which can be set under
Outdoor temp. max. valve position).
25%
100%
0%
T
OA
Heating output
Outdoor temp.
max. valve position
Max. valve position
1
03
85
D
17
en
_0
1
Outdoor temp.
0% valve position
Thermic
Motoric
The controller adds the values representing the valve position for downdraft
compensation and the valve position for the heating sequence.
– If the room temperature rises as a result of the downdraft compensation feature, the
heating sequence reduces the opening of the associated valve, so correcting the
room temperature.
– When the sequence reaches zero, the room temperature is increased by the residual
heat from the downdraft compensation feature.
The heat output calculated by the controller is achieved as follows:
LTHW radiators with
motorized
valve actuators
The valve is opened to the heat output value [%].
KNX
R
CO
Note
Function
Note
Controller output
