Installation
Wiring
1
8 | 22
Siemens
A6V11478123_en_a
Building Technologies
2019-02-01
1.4
Wiring
1.4.1
Electrical grounding
Note the following grounding situation of the QBM97.
●
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.
Transformer
Power-
supply
24V
≂
0V
REF B- A+
Earth
Sensor module
Not isolated RS485
M
Situation
Consequences
