Free Tool · UL 508A Supplement SB
Calculate your control panel's SCCR with the weakest-link method. Free, instant, no signup required to see your result.
Use the rating from the device label or datasheet. "Default" fills the UL 508A Table SB4.1 default for that component type.
The short-circuit current rating is the maximum fault current a panel can safely withstand. NEC 409.22 prohibits installing a panel where available fault current exceeds its marked SCCR.
Per UL 508A Supplement SB, the assembly rating equals the lowest-rated component in the power circuit. One 5kA device caps a panel full of 65kA gear at 5kA.
Current-limiting fuses, higher-rated components, and tested combinations lift the assembly rating. That's design engineering — our team does it daily.
At minimum, equal to the available fault current at your installation point. Many industrial sites need 35–65kA. When in doubt, get the utility's fault current data — or send it to us with a quote request.
UL 508A Table SB4.1 assigns defaults — commonly 5kA for many device classes and 10kA for terminal blocks.
No — results are informational. Final ratings require review of the actual assembly and protection coordination, which is exactly what our design service provides.
Yes — we evaluate, re-work, and mark existing panels under our UL 508A program. Start with a quote request.
Panels engineered to 65kA+ SCCR — designed and built in our UL 508A shop.
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