Siemens S7-400 Installation Manual page 43

Note
Do not use any cyclinder-head screws longer than 6 mm for the connection to the
reference point. Otherwise, you may create an undesired connection between the
reference point and the rack profile behind it and therefore the connection for the
chassis ground.
The following figure shows the position of the reference point on a rack up
after 10/99.
Metallic connection, undo
from above in the case of
ungrounded configuration
Load voltage ground con-
nection (reference point)
The following figure shows the ground connection to the reference point.
S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04
Chassis ground terminal
Spring washer
M4 screw
Installing the S7-400
1 2
Threaded hole
Terminal
3 4 5 6 7
2-17