The way I see it is that the CONTROL PANEL must be marked with an SCCR and cannot be installed where the Available Fault Current is greater than that marked amount. Nowhere in any calculations of Available Fault Current is there any mention of using Current Limiting Fuses to alter that value; impedance, resistance, yes, fuse clearing time is not mentioned. Case in point; try to find a place to load a fuse current limitation value into SKM or ETAP engineering software for determining AFC... it's not there. BUT, if I'm wrong about this last point, someone tell me, I'm all ears.
The PANEL MANUFACTURER can use CL fuses as part of their methodology in determining the SCCR of the panel, because they can carefully coordinate the let-through of the fuses under the right circumstances against the withstand ratings of the components used on the power train. That is their job here. Those fuses CAN be located outside of the panel now, so long as the label on the panel, WHERE THE HIGHER SCCR IS LISTED, clearly dictates that those specific fuses MUST be used. But that is still the responsibility of the panel mfr. A contractor in the field is not changing the marked SCCR of the panel by adding CL fuses (that the panel mfr didn't specify) and the contractor in the field is not able to change the AFC by adding CL fuses either. There just is no provision in the NEC that allows this to happen. Maybe nobody thought it necessary because, again, attaining a higher SCCR is not that difficult, but maybe nobody realized just how lazy some mfrs would be with this.
Should there be a way to use CL fuses in the field? Maybe. One place to start is to add a definition of "Available Fault Current" to the next NEC. As of the 2017 code there isn't one, yet the term "available fault current" is used many times throughout the Code. It might be time to define it more clearly. If that definition allows for the use of current limiting fuses or breakers to be used in that calculation, so be it. But until that happens, it's not there.
