AIC compliant

[electrofelon]

I want to make sure I understand this fully. I fully understand series ratings, use them all the time, look up rated combinations, etc. But it seems to me use of a current limiting fuse is different (see the definition in 240.2). So what prohibits me from reference the manufacturers data on a current limiting fuse, and using it for a situation like in the OP? Maybe I am wrong, but I dont see it falling under 240.86. The only other thing I can find in the NEC is 110.9 and 110.10. Is a current limiting fuse not listed for a use in less tested?

 

[Jraef]

So what prohibits me from reference the manufacturers data on a current limiting fuse, and using it for a situation like in the OP?

Nothing, if you are a UL508A panel shop following ALL of UL 508A Supplement SB rules regarding how this is done and will be LISTING the rating on the outside of the panel, or are a Registered PE willing to sign off on the concept. The ONLY "acceptable method" of determining the SCCR of a piece of equipment mentioned in the NEC is UL 508A Supplement SB; it doesn't really actually say the part about a PE signing off on it, but it's a generally accepted method IF you find one to do it.

Unfortunately for the OP, he has a panel that ALREADY has an SCCR listing on it, of 5kA. So he is now stuck with that. The NEC makes no allowance for "rolling your own", none. It simply says;

409.22 Short-Circuit Current Rating. An industrial control
panel shall not be installed where the available fault
current exceeds its short-circuit current rating as marked in
accordance with 409.] 10(4).

 

[electrofelon]

Nothing, if you are a UL508A panel shop following ALL of UL 508A Supplement SB rules regarding how this is done and will be LISTING the rating on the outside of the panel, or are a Registered PE willing to sign off on the concept. The ONLY "acceptable method" of determining the SCCR of a piece of equipment mentioned in the NEC is UL 508A Supplement SB; it doesn't really actually say the part about a PE signing off on it, but it's a generally accepted method IF you find one to do it.

Unfortunately for the OP, he has a panel that ALREADY has an SCCR listing on it, of 5kA. So he is now stuck with that. The NEC makes no allowance for "rolling your own", none. It simply says;

Ok fair enough. But expand the topic to say something other than a control panel. Say another piece of equipment, or a non fused disconnect with a 10k SCCR. What does the inspector cite me with when I use a current limiting fuse along with the manufacturers data to lower the fault current at to the equipment rating?

 

[Jraef]

Ok fair enough. But expand the topic to say something other than a control panel. Say another piece of equipment, or a non fused disconnect with a 10k SCCR. What does the inspector cite me with when I use a current limiting fuse along with the manufacturers data to lower the fault current at to the equipment rating?

I can't speak to what any AHJ will / can write you up for, because at a basic level, they can always fall back on 110.3, "Suitability for installation and use in conformity with the provisions of this Code". Maybe 110.10 though, because the way that last sentence is worded, "Listed equipment applied in accordance with their listing shall be considered to meet the requirements of this section." indirectly implies that if equipment is NOT listed that way, it fails. So your non-fused 10kA SCCR disconnect switch is no more than it says, 10kA.

That said, maybe it's a poor example because in this particular case, many (if not most) UL98 listed non-fused disconnect switches are no different than the fused versions, so the mfr will have a listing saying that if you use the same fuses in the circuit, it has an equivalent series SCCR rating as the fused version. So again, it really comes down to how the equipment involved is listed. There are no generalizations you can make, other than "you need to pay attention to the issue".