AIC Rating

[buzzlectric]

Help me understand the AIC rating of a breaker or fuse, is the # (10k,22k) when it opens up or the amount it will withstand without explosion? I have had this explained to me many different ways, none with the same answer.

 

[bphgravity]

Read 110.9 of the NEC along with the definition of "interupting rating" in Article 100.

 

[davidr43229]

Help me understand the AIC rating of a breaker or fuse, is the # (10k,22k) when it opens up or the amount it will withstand without explosion

AIC is Ampere Interrupting Rating, it means that the Overcurrent Protection Device (OCPD) is capable of Interrupting that much available fault current, without extensive damage to that OCPD.
Just my $.02

 

[mdshunk]

... or the amount it will withstand without explosion?

That's the long and the short of it. Maybe not explosion, but maybe more like surviving without damage. Surviving without explosion would be a good thing to keep in mind, because this would cause awareness of AIC ratings to stick in your head better.

 

[buzzlectric]

OK, thats what i thought it was, now how does this affect the Hazard/Risk levels that dictate the PPE level of protection?

 

[bphgravity]

Do you have a copy of the NFPA 70E?

 

[buzzlectric]

Not Yet, will soon.

 

[mdshunk]

Not Yet, will soon.

Now you do. View it for free here: http://www.nfpa.org/freecodes/free_access_agreement.asp?id=70E04

 

[bphgravity]

Buzz, your questions are so broad that any answer would leave you with more questions than you probly have right now. Perform a search on this or on the web in general. You will get much better and comprehensive information than you will from the two questions you have asked under this topic.

Is this leading to an specific issue or problem you are dealing with at work or are you just fishing around for some education?

 

[jim dungar]

In general it would be prudent to assume that if a device cannot safely interrupt an arc then it cannot clear the arc in a timely manner which will result in higher arc flash incident energy.

 

[Jraef]

The AIC rating of a breaker has no direct relation to the Arc Flash potential in an enclosure. Indirectly though, if you have a lower AIC rating it usually means (or should anyway) that there is less potential energy at that panel to begin with, so when calculating the" arc flash protection boundary" and then the "incident energy exposure", you are somewhat starting off knowing that the panel is being used in a lower risk environment in the first place. That's not universal however, because you can have series rating on equipment, where the main may be current limiting so that smaller branch devices can have lower AIC ratings, however if the main is in the same box, the energy calculations would need to be done based on that.

Look at the calculation methods laid out in section 130.3, it will give you an idea of how the AIC rating will indirectly relate to these calculations.

 

[ron]

In many cases, depending on the time-current characteristics of the upstream device, the lower fault current will result in higher incident energy (and PPE selection) because it takes the protective device longer to clear the fault. There is however a sweet spot where lower fault current will result in lower incident energy but it must be calculated.