View Full Version : AIC rating of breakers

October 2nd, 2007, 04:58 PM
When adding a sub-panel, does the AIC rating of the main service panel and/or breakers affect the choice of sub-panel and/or breakers in that sub-panel?

I've tried to find enough info on this subject, maybe it doesn't matter if there are 10,000 AIC breakers in main panel, with 22,000 AIC breakers in Sub?

Am I missing something? I'm sure I am. Or making a lot out of nothing?


October 2nd, 2007, 06:18 PM
Most residential stuff is rated at 10K AIC. There is nothing wrong with putting in equipment with a higher AIC rating. You have to install panels and breakers rated for what they need to withstand. It is difficult to have to withstand more than a 10K AIC requirement in a residential setting. It takes larger (and usually shorter) wires and bigger transformers to get over 10 KAIC.

If you had a need to have a 24 K AIC system, if you stay within a family of "series rated" components (rated by the manufacturer and usually only with thier own stuff), a 24KAIC main panel can protect a subpanel to 24 KAIC even if there are only 10KAIC rated breakers in it and the 24K rated main lists the feeder breaker as a legal series rated combination. So you'd usually put the higher rated stuff upstream if this was even an issue.

My 400A service is limited to 10KAIC because the meterbase is only rated at 10KAIC. The main panel is 24 KAIC and the subpanels are all series rated to 24 KAIC even though they only have 10K AIC breakers.

October 2nd, 2007, 11:17 PM

As usual, I knew I'd find the answer here. So, really, there is no choice to be made when adding on. Figured I was chasing something that didn't matter, but I had to know.


October 3rd, 2007, 11:35 AM
Can any DIYers break the riddles:
1. AIC

Side note: we should start spelling out the initals. I guess we all do it, but looking important isn't helping anyone, and this includes me! :musicus:

AIC could mean: Aerospace Intergration Corporation (Not advertising)

October 3rd, 2007, 12:03 PM
Easily found on the internet. :hello:



credit to: L. W. Brittian, Mechanical-Electrical Instructor
from www.maintenanceresources.com

Circuit breakers are tested and then rated as to their ability to open the protected circuit with a specific amount of current flowing in the circuit. Circuit breakers typically have AIC ratings of between 5,000 and 200,000 AIC. The amount of fault current available must not exceed the breaker’s ability to safely open the circuit. Not only must the breaker be rated for the applied voltage, and continuous amperage load; it must also have an AIC rating equal to or greater than the available current at the location in the circuit where it will be installed. Breakers that have been installed so that the available fault current exceeds its AIC rating may blow up, just like a bomb would explode were it to attempt to clear a fault current above its rating. When opening a faulted circuit, it is possible for smoke and fire to be exhausted from a breaker. If you would like to see a breaker belch fire and smoke, see if you can locate and view the Cooper-Bussmann fuse company videotape titled “Specification Grade Protection”. The visual impact of this tape will likely enhance your appreciation of the importance of an electrical device’s AIC rating far better than any words of mine.

credit to: L. W. Brittian, Mechanical-Electrical Instructor
from www.maintenanceresources.com

October 3rd, 2007, 04:08 PM
Just goes to show the power of knowledge and the ability to get that knowledge on the internet while watching the kids play, the husband wash dishes and the woman of the house having the hard job of multitasking all this and looking up knowledge on the internet and being the supervisor all at the same time. Tough but someone has to do it ! Ha Ha

Now I am being a bit non behaving ?


October 3rd, 2007, 10:42 PM
I should rephrase my comment to "it doesn't matter in my application", because hopefully my main breaker, which I'm not changing, should have been properly spec'ed at installation. I'm sure it was ;). It was easy to find what the AIC definition was, enough manufacturers have this info on their web sites. Deciphering how breakers of differing ratings interact is a bit confusing. Also, knowing what the available fault current is in my area might be hard to determine. The power company should have that info, but getting to talk to a real person can be a bit trying at times.

Basically, as a DIYer myself, I stumbled across this and just wanted to verify if I should be concerned with spec'ing breakers for my subpanel or not. Or just pull them off the shelf at the big orange box and be done with it.

Thanks for the responses. If there is anything that us DIYers need to know, please enlighten us some more. Where I live there is only a neighborhood requirement for inspection, no city or county inspections.


October 3rd, 2007, 11:26 PM
For residential services at 400A or below, a 10K AIC system will be fine. I think all breakers have their AIC rating on them somewhere (and anything modern I've seen for home use is 10KAIC at least). Unlabeled ones are at least 5000 AIC.

I doubt your meter is rated over 10KAIC, so that would be your upper limit for the source supply.