Operating Instructions

Table Of Contents
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Siemens RXB (KNX) application library RXB Description of functions for FC-10, FC-11, FC-12, FC-13 CM110385en_08
Building Technologies Control sequences 2013-06-17
8.4.4 Radiator valve actuator override
See also section 8.1.7.
For test purposes, the radiator valve actuator can be overridden via the following
communication objects:
Heating surface output override (Input communication object)
Flags
Type Receive timeout Value
R
W
K
T
U
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 145).
8.4.5 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
10385D17en_01
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.
CO
Note
Function
Note