If catalog permits only certain operating positions, it means that other positions are not validated due to following reason:
a) product functionality might be affected due to gravity force applied from side/back/bottom-up etc.
b) different heat distribution inside the product that can lead to:
b1) product burning or
b2) rated parameter cannot be achieved

If we focus on ATS01 and ATSU01 (up to ATS01N232 size) then:
- no risk of ATS damage or loosing the functionality.
- heat distribution is different but if we take a look on dismantled ATS (in attachment) we can see that PCB is on left side, while heatsink for power components heads to the right. From this perspective if you rotate ATS by 90 degrees ccw (counter clock wise), the PCB will be down and heatsinks heading up and moreover the ATS perforated side will be up. The heat transfer will be even better than in normal position.

Conclusion: Vertical position rotated by 90 degrees ccw is validated providing that there is at least few cm (2-3cm) free space above ATS.
In any case:
- do not place another ATS above that ATS (or at least 10cm vertical gap between them)
- do not rotate ATS by 90 degrees cw (clock wise) because the PCB would be up and it would impair proper heat transfer. ATS may work, but with less current and we do not have derating table for it.
- do not apply this position for other ATS, like old big ATS01N244.

Released for: Schneider Electric Philippines