UL 508 A: Industrial Control Panels

Appendix D: Bus Bar System


Appendix D was introduced in April 2020 version of UL 508A. It makes clear what was before a common practice but not formally correct. That means an industrial control panel manufacturer is obliged neither to use a certified bus bar system nor to perform short circuit test, provided it complies with TABLE G3.1 of UL 891 (named Table D3.1 in UL 508A).

That table is now included in the new appendix and that makes it formally possible that practice.


The table distinguishes between bus bars set as Face to Face or Edge to Edge.

For example, in case of bus bars set Edge to Edge, if the distance between insulators is not more than 533 mm, provided the size of the bar complies with table D3.1, and the rest of the architecture complies with SUPPLEMENT SB (all components having a SCCR equal to 50 kA), the panel can be declared with SCCR = 50 kA.

Safety in Collaborative Robotics

There is no “Collaborative Robot”. That is one of the first statements you hear from people working in Collaborative Robotics. The reason is because the robot can be designed for a collaborative task, but it is the Application that makes the “Robot Collaborative”. The reference standard for Collabo