7. Final Rule Summary Panel SCCR = - Lowest SCCR in power circuit (default method) OR - SCCR of current-limiting fuse if all downstream components: a) Have SCCR ≥ 5 kA, and b) Are not power conversion equipment (VFDs, etc.), and c) Manufacturer series rating exists or UL 508A Table SB4.2 allows it. 8. Quick Formula for Engineers Without current-limiting: [ SCCR_panel = \min(SCCR_1, SCCR_2, ..., SCCR_n) ]
If ( SCCR_fuse \geq 100 \text kA ) and ( SCCR_component \geq 5 \text kA ), then ( SCCR_effective = SCCR_fuse ) for that branch. sccr calculation
If available fault = 50 kA → let-through I²t and peak current correspond to a for downstream components. It is not a calculation of available fault
The Short-Circuit Current Rating is the maximum symmetrical fault current (in kA) that a component or assembly can safely withstand without creating a safety hazard (e.g., arc flash, fire, or explosion). It is not a calculation of available fault current from the utility; it is a rating of the equipment. sccr calculation
For a 5 kA rated contactor, if the let-through I²t of the fuse ≤ the I²t withstand of the contactor (or per Table SB 4.1), the contactor can be considered rated at (e.g., 200 kA) but only if the manufacturer allows series rating.