Siemens SIMATIC RF186C Operating Instructions Manual page 38

Connection
5.3 Connect CM to functional ground (PE)
Mounting
Proceed as follows to connect the communications module to functional ground via a ground
conductor:
1. Drill 2 mounting holes with a distance of 155.6 mm.
2. Insulate the ground conductor.
3. Attach the cable lug to the ground conductor.
4. Screw the module and the cable lug together with the M4 fastening screws with a torque
of 1.2 Nm.
NOTICE
Grounding with non-conductive mounting base
Ensure a low impedance connection between the communications module and functional
ground.
Figure 5-8
38
Mounting the CM on a non-conductive base / connection to functional ground
SIMATIC RF185C, RF186C, RF188C, RF186CI, RF188CI
Operating Instructions, 06/2019, C79000-G8976-C512-02