SCCR rating solution

Dear all, first of all I would like to say thank you to all members. I learn every time more and more.
But as always I have questions about the SCCR rating (UL508A) for panels.

The moment I have a cabinet which is supplied from external source (plug, cord connected) where the only information I have is 120V/60Hz/20A.
This line runs into a pressure controller which has two relay contacts to switch the power (L and N). After these two contacts the line is wired direct to an AC/DC converter from Siemens SITOP PSU100M. Output 24 VDC is wired direct to a selctivity module SITOP PSE200U.
All equipment inside is supplied with 24 VDC. So I only have the 120V circuit which ends at the PSU.

I don't understand how to give a SCCR rating for this cabinet. I cannot find any SCCR information labeled at the PSU.

My second question refers to a supply also via plugs because it is also a movable plant.
Here I have a main supply 3x480V/60/Hz, pre-fuse is 3x25A and a circuit 120V/60 Hz. max. fused 10A.
The 480V line supplies a PSU 480VAC/24VDC and via a manual motor controller eaton PKZM0 and a contactor to a motor agitator.
I believe the only way I need to check is the line to the motor, or?

But what's about the 120V line? This supplies an electronic pressure controller with two contacts and after the contacts a contactor to switch the 480V into the cabinet. Also a vessel light is supplied from the 120V line, fused with 2A. Do I need here also a SCCR rating? The pressure switch has no SCCR rating.

I hope you can help me with some helpful notes and information.

Thanks for your feedback and stay healthy.


Staff member
San Francisco Bay Area, CA, USA
Electrical Engineer
SCCR ratings are only required for power circuits, not control circuits.
This ^^^

And even if you wanted to consider the 120V as "power" since it is the highest voltage in the panel, you could just list the SCCR as 5kA without having to test or calculate anything. It would be very difficult to get more than 5kA in available fault current out to a 120V circuit on something plugged into an outlet.