Siemens SIMATIC S7-400 Hardware And Installation Manual page 33

The figure below shows how much space you must allow for when assembling an
S7-400 from two racks with a cable duct or fan subassembly. This requirement is
increased by a height of 400 mm for each additional rack with a cable duct or fan
subassembly.
840 mm
Mounting depth, fitted: 237 mm max.
Note
A minimum clearance as shown in the above figure between rack and cable duct
or fan subassembly must not be provided, but is essential between two adjacent
racks and between racks and other equipment.
S7-400 and M7-400 Programmable Controllers, Installation Manual
C79000-G7076-C424-01
www.gkbpx.com
Cable duct/fan subassambly
Cable duct/fan subassambly
Installing the S7-400
19-inch reference level
2-13