3/6
Siemens Building Technologies
Room sensors QFA20…
CE1N1857en
HVAC Products
06.06.2005
R1
0 V
5 V
10 V
5 V
5 V
0 V
5 V
10 V
U1
U2
BS-MS
75 °C
35 °C
20 °C
R1
R2
R3
R2
R3
20 °C
Measuring range
Test function active
18
57
Z
0
1
e
n
The setting element is accessible after removing the baseplate. It consists of 6 pins and
a shorting plug. It is used to select the required measuring range and to activate the
test function.
The different plug positions have the following meaning
•
For the passive temperature measuring range:
Shorting plug in the mid position (R2) = LG-Ni 1000 or T1
•
For the activating temperature measuring range:
Shorting plug in the upper position (R1) =
−
35...
+
35 °C,
Shorting plug in the mid position (R2) = 0...50 °C (factory setting),
Shorting plug in the lower position (R3) = 0...50 °C
•
For activating the test function:
Shorting plug in the vertical position: The values according to the table "Test function
active" will be made available at the signal output.
•
Should the temperature sensor become faulty, there will be after 60 seconds a volt-
age of 0 V at signal output U2 or signal output BS-MS
−
35 °C, and the humidity
signal at signal output U1 will reach 10 V
•
Should the humidity sensor become faulty, there will be a voltage of 10 V at signal
output U1 after 60 seconds, and the temperature signal will remain active
Engineering notes
To power the sensor, a transformer for safety extra low-voltage (SELV) with separate
windings for 100 % duty is required. When sizing and protecting the transformer, the
local safety regulations must be observed.
When sizing the transformer, the power consumption of the room sensor must be taken
into consideration.
For correct wiring of the sensor, refer to the Data Sheets of the devices with which the
sensor is used.
The permissible line lengths must be observed.
When laying the cables, it must be observed that the longer the cables run side by side
and the smaller the distance between them, the greater the electrical interference.
Shielded cables must be used in environments with EMC problems.
Twisted pair cables are required for the secondary supply lines and the signal lines.
Fitting notes
On an inner wall of the space to be air conditioned. Not in recesseds, shelves, not be-
hind curtains, not opposite or near heat sources.
The unit must not be exposed to spot lights or direct solar radiation.
The end of the conduit at the sensor must be sealed to prevent false measurements
due to draughts through the conduit.
Installation instructions are printed on the packing.
Setting element
Fault
Cable routing and
cable selection
Location
Installation instructions