X20 system 
3.3.2 Vertical installation
1)
 n ... Number of modules
Figure 4: X20 system - Vertical installation
For optimal cooling and air circulation, there must be at least 35 mm free space above the modules. To the left
and right of the X20 system, there must be at least 10 mm of free space. Underneath the modules, 35 mm space
must be left free for I/O and power supply cabling.
Notice!
The controller must be secured against slipping.
An end bracket or ground terminal can be used for securing.
To fixate mechanically, B&R offers and recommends the use of accessory end clamps:
Figure 5: X20AC0RF1 set - End clamp for TH35 top-hat rail
12 Installation / EMC guide  1.36 (April 2021)