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Siemens
RXB (KNX) application library
FNC Description of functions for FC-10, FC-11, FC-12
CM110385en_05
Building Technologies
Temperature measurement
28 Feb 2009
7 Temperature
measurement
7.1
Room temperature measurement
The value valid for temperature control can originate in various sources:
– A room unit via PPS2
– An analog sensor via analog input B1
– Mean value of several sensors
–
The
bus.
If none of these sources supplies a valid room temperature, the following will happen:
•
the controller uses the mean value from the effective heating and cooling setpoints
for control until a valid measured value is again received
•
the controller issues an alarm "Room temp. sensor error"
•
the bus output sends 0°C
•
if slaves are connected, they receive an invalid temperatur (327.67°C)
•
if a room unit is connected to a slave, the slave uses the temperature value of its
room unit when two heartbeat periods have elapsed.
7.1.1
Local temperature sensor at PPS2 interface
PPS2 (CP+, CP-)
QAX3...
RXB2...
103
8
5Z
1
2
If a QAX … room unit (with a PPS2
interface) is connected to the controller, the
room temperature is measured by the
temperature sensor built into the room unit.
7.1.2
Local temperature sensor at analog input
B1
QAA24
RXB2...
10
38
5Z
1
3
Alternatively, an LG-Ni1000 sensor, type
QAA24, may be connected to analog input B1
of the room controller.
The sensors connected to terminal B1 can be tasked with different functions:
Parameter setting
Description
Room
Room indoor air sensor (can also be used for
averaging, see below).
Return air
Return air sensor
(refer also to Section 9.2.4, "Periodic fan kick")
No sensor
No sensor connected
(basic setting, except for FNC08)
Only measured value
acquisition
Uses the signal, see "analog input B1", page 138.
Supply air (cascade)
Supply air temperature for cascade control.
The sensor is automatically configured as a supply air
sensor if application FNC08 is selected.
Sources
Invalid temperature
