Data Sheet for Product

5/10
Siemens Differential pressure sensor QBM3020.. / QBM3120.. CA1N1916en01
Smart Infrastructure 2019-10-09
Engineering notes
The transformer used must be suited for safety extra low voltage (SELV) when using an
AC power supply. It must have separate windings and be designed for 100 % duty.
Transformer size and fuse must comply with local safety regulations.
Observe maximum permissible cable lengths.
If cable lengths exceed 50 meters and run parallel to the mains cables: Use shielded
cables!
Mounting and Installation notes
The differential pressure sensor is suited for direct mounting on air ducts, walls, ceil-
ings, or in control panels.
The supplied 2 meter plastic tubing can be modified to the duct connection on the plant.
To achieve the housing protective class indicated under "Technical data", the differen-
tial pressure sensors must be mounted with the pressure nipple facing down. In addi-
tion, they should be higher than the air duct probes.
If the pressure connection nipples point upward or are at a lower level than the
air duct probes, condensation can collect inside the sensor, causing damage to
the device.
The pressure tubing for the sensor nipples are connected as follows to the differential
pressure sensors:
On the air duct side
On the pressure sensor side
Tubing with higher pressure side
(lower vacuum)
Connect to pressure nipple "P1" or "
+
"
Tubing with lower pressure side
(higher vacuum)
Connect to pressure nipple "P2" or "
−
"
The sensor is supplied with mounting instructions.
For detailed information on installation and mounting position, refer to the
Sensor In-
stallation Guide in BT download center.
• Power supply by SELV or class 2 power supply with limited output of 15 W or less
(UL requirement)
• Use only copper wiring
Caution
Note
Caution