Wiring; Electrical Grounding - Siemens QBM97 Series User Manual

Installation
1

Wiring

1.4 Wiring

1.4.1 Electrical grounding

Situation
Consequences
8 | 22
Siemens
Building Technologies
Note the following grounding situation of the QBM97.
Power-
supply
24V
Transformer
● QBM97 uses a non isolated RS485-Interface
● The reference of RS485 transceiver is connected to GND
● all GND pins are on the same potential
● if the Climatix controller and QBM97 are connected to the same power source,
take care to avoid miswiring between 24 V input and GND
The document "Modbus communication" (J3960) provides profound information
on Modbus grounding.
REF B- A+
M
Not isolated RS485
≂
0V
Sensor module
Earth
A6V11478123_en_a
2019-02-01