AIC Ratings

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Dvelasco626

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Los Angeles
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Electrician
Hello guys, I have a question that’s been breaking my brain for a couple of days. So I have an ATS that is supposed to be braced for 30kaic. The breaker I’m using, according to the specs, gives me 65kaic at 240v. But the inspector says I’m only braced for 22kaic. The bracing would be at 22kaic if we were using 600v. But we are using 240v so we should be at 65kaic right? Can anyone help me figure out if the breaker I’m using is the correct one?

Breaker Ratings for 400amp 600v Max:
400amps-240v-65ka
400amps-480v-35ka
400amps-600v-25ka
 
Dvelasco626 said:
Hello guys, I have a question that’s been breaking my brain for a couple of days. So I have an ATS that is supposed to be braced for 30kaic. The breaker I’m using, according to the specs, gives me 65kaic at 240v. But the inspector says I’m only braced for 22kaic. The bracing would be at 22kaic if we were using 600v. But we are using 240v so we should be at 65kaic right? Can anyone help me figure out if the breaker I’m using is the correct one?

Breaker Ratings for 400amp 600v Max:
400amps-240v-65ka
400amps-480v-35ka
400amps-600v-25ka
Click to expand...
What exactly is the breaker you are referring to? Is that in the ATS? I think you would need to look at what the actual ATS instructions say for a AIC and sccr ratings.
 
The problem is that the inspector is saying that because the breaker has a maximum voltage rating of 600v, he is rating it at 600v which only gives me 25kaic. But, we are only using 240v which technically should rate the breaker at 65kaic
 
Dvelasco626 said:
The problem is that the inspector is saying that because the breaker has a maximum voltage rating of 600v, he is rating it at 600v which only gives me 25kaic. But, we are only using 240v which technically should rate the breaker at 65kaic
Click to expand...
Sounds like another inspector who should be fired then. Why would they provided different ratings at different voltages if you always had to use the max anyway🤔.
 
If this is only about the AIC rating, then you are correct; the rating is based on the voltage that it is being USED FOR.

You also however used the term "bracing" which is different. Bracing or bus bars is the same regardless of voltage. So if you put a breaker rated for 65kAIC into a bus system that was braced for 22kA, the system could not have an SCCR of greater than 22kA. I don't know if that's the case here or not without data on the ATS, I'm just pointing out the semantics issue here.

IC = Interrupting Capacity (in Amps, hence AIC) of an interrupting device, like a circuit breaker or fuse. This is the maximum mechanical forces that the device can safely handle, and the forces are based on ENERGY, not just current, hence the current capability going up as the voltage goes down.

Bracing = the mechanical strength of bus bar supports or other current carrying components to handle the magnetic attraction and repulsion forces that take place during a fault UNTIL the interrupting device clears it. Because it is based on magnetics, it is only related to current, not voltage.

Short Circuit Current Rating (SCCR) = the total current that a device or system can safely handle during a fault event, basically a combination of the IC of any interrupting device AND the bracing of any current carrying components. This is what we used to call the "Withstand Rating" and can be affected by the "let-through" current of any current limiting devices that are part of the system or up stream of it, so long as it was TESTED AND LISTED that way.
 
Jraef said:
If this is only about the AIC rating, then you are correct; the rating is based on the voltage that it is being USED FOR.

You also however used the term "bracing" which is different. Bracing or bus bars is the same regardless of voltage. So if you put a breaker rated for 65kAIC into a bus system that was braced for 22kA, the system could not have an SCCR of greater than 22kA. I don't know if that's the case here or not without data on the ATS, I'm just pointing out the semantics issue here.

IC = Interrupting Capacity (in Amps, hence AIC) of an interrupting device, like a circuit breaker or fuse. This is the maximum mechanical forces that the device can safely handle, and the forces are based on ENERGY, not just current, hence the current capability going up as the voltage goes down.

Bracing = the mechanical strength of bus bar supports or other current carrying components to handle the magnetic attraction and repulsion forces that take place during a fault UNTIL the interrupting device clears it. Because it is based on magnetics, it is only related to current, not voltage.

Short Circuit Current Rating (SCCR) = the total current that a device or system can safely handle during a fault event, basically a combination of the IC of any interrupting device AND the bracing of any current carrying components. This is what we used to call the "Withstand Rating" and can be affected by the "let-through" current of any current limiting devices that are part of the system or up stream of it, so long as it was TESTED AND LISTED that way.
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Thank you for this information. Very helpful. Let me get more information on the busbars brace rating and I will be back on here. I think, based on the information you’ve provided, I’m pretty sure the bus bar the breaker is on has a higher capacity then the breaker itself. I hope I’m understanding correctly. But let me verify some information based on this comment. Thanks again.
 
The magnetic force on bus bars and other equipment is proportional to the square of the current. The maximum possible fault current occurs during what is called a bolted fault condition. In circuits without a lot of large reactive equipment (motors) we can get to a quick estimate using the “infinite bus assumption. If we have say a 150 kVA transformer with a 480 V wye secondary and a 1% impedance first we can calculate the rates current as 150x1000 / 1.732 (3 phase) / 480 = 180 A. Short circuit maximum at the transformer terminals would be 180 / 1%Z or 18 kA. Now any impedance can reduce this further either due to the fact that the primary side of the transformer may have some impedance or due to wiring on the secondary side. In addition large reactances (motors) can act as sources and increase the fault current.

Notice that breakers and fuses have nothing to do with it unless they are acting as current limiting and generally speaking breakers aren’t usually significantly current limiting.

Then as others stated depending on the withstand rating (AIC) of the equipment either it is in danger of being magnetically compromised or not,

The inspector is reading things wrong or looking at a bus bar.
 
paulengr said:
The magnetic force on bus bars and other equipment is proportional to the square of the current. The maximum possible fault current occurs during what is called a bolted fault condition. In circuits without a lot of large reactive equipment (motors) we can get to a quick estimate using the “infinite bus assumption. If we have say a 150 kVA transformer with a 480 V wye secondary and a 1% impedance first we can calculate the rates current as 150x1000 / 1.732 (3 phase) / 480 = 180 A. Short circuit maximum at the transformer terminals would be 180 / 1%Z or 18 kA. Now any impedance can reduce this further either due to the fact that the primary side of the transformer may have some impedance or due to wiring on the secondary side. In addition large reactances (motors) can act as sources and increase the fault current.

Notice that breakers and fuses have nothing to do with it unless they are acting as current limiting and generally speaking breakers aren’t usually significantly current limiting.

Then as others stated depending on the withstand rating (AIC) of the equipment either it is in danger of being magnetically compromised or not,

The inspector is reading things wrong or looking at a bus bar.
Click to expand...
Thank you for this information. Every answer has been helpful. I will keep looking into this in preparation for my next inspection.
 
Basically the breaker is a component that can be used in other assemblies. The breaker itself is good for 65k (at 240 volts) if whatever assembly it is installed in also series rated to go with it. Additional information on the ATS is needed to know if you can use it up to 65 kA or not in this assembly.
 
one question here in same topic
the main panel main breaker is rated for 22KAIC,400A main panel Eaton.
usually KAIC RATING LISTED IN eaton BR breakers are 10kAIC
Now the plan reviewer wants us to revise the plans to show eaton BR breaker to be rated 22kaic as well For the solar breaker 40A.

so as per the above discussion the breaker itself is rated for 600 volts, means 240 volts should be rated for up to 65 KAIC?
What's the calculation involved here, can somebody please help me understand this. so I can convince plan reviewer.
 
I don't know what you are trying to accomplish. You can not change AIC ratings in the field, they can only come from the manufacturer.

Does the plan reviewer want to see some type of certification for a series rating?
Are they looking for the solar breaker to be fully rated?
 
jim dungar said:
I don't know what you are trying to accomplish. You can not change AIC ratings in the field, they can only come from the manufacturer.

Does the plan reviewer want to see some type of certification for a series rating?
Are they looking for the solar breaker to be fully rated?
Click to expand...
jim i understand that,
Plan reviewer comment is that if main breaker has 22kAIC rating then the solar breaker also should have same interrupt ratings.
I Just dont undesrtand that from where did he get that information
So whats the solution here do Eaton even make breakers that are rated 22KAIC FOR 240 VOLTS.
 
Does any of this even matter? What is your available fault current? Is it over 10K amps? Is it over 20KA?
Eaton BR branch breakers are series combination rated with certain main breakers. The panel should provide a list of the series combination rating with a given main and branch breaker type.

Here is a list of their series combination ratings: https://www.eaton.com/content/dam/e...eries-rating/series-rating-information-br.pdf
This one is more detailed: https://www.eaton.com/content/dam/e...ries-rating-information-manual-1c96944h02.pdf
 
Designer101 said:
jim i understand that,
Plan reviewer comment is that if main breaker has 22kAIC rating then the solar breaker also should have same interrupt ratings.
I Just dont undesrtand that from where did he get that information
So whats the solution here do Eaton even make breakers that are rated 22KAIC FOR 240 VOLTS.
Click to expand...
I'm also unclear what you have going on. Is the solar breaker you talking about a backfed breaker that is after the main or is it a supply side connection? If the former, as suemarkp said you could investigate whether there is a series rating. If the latter, then the PV breaker needs to be rated for the available fault current. It is common (although of course not always correct) to assume the existing equipment was properly selected and go by that value instead of investigating the available fault current.

Yes Eaton makes 22kaic breakers. For example in the BR line, it's a BRH240
 
jim dungar said:
I don't know what you are trying to accomplish. You can not change AIC ratings in the field, they can only come from the manufacturer.

Does the plan reviewer want to see some type of certification for a series rating?
Are they looking for the solar breaker to be fully rated?
Click to expand...
Per plan reviewer he wants to see solar breaker rated at 22 kaic, this home is in building phase there is no main panel installed yet.
 
electrofelon said:
I'm also unclear what you have going on. Is the solar breaker you talking about a backfed breaker that is after the main or is it a supply side connection? If the former, as suemarkp said you could investigate whether there is a series rating. If the latter, then the PV breaker needs to be rated for the available fault current. It is common (although of course not always correct) to assume the existing equipment was properly selected and go by that value instead of investigating the available fault current.

Yes Eaton makes 22kaic breakers. For example in the BR line, it's a BRH240
Click to expand...
its a back feed breaker, I am not sure about he fault current as this has not been constructed yet, the building is in construction phase.

Thank you plan reviewer want us to use solar breaker hat has same KAIC rating as main disconnect
 
Designer101 said:
jim i understand that,
Plan reviewer comment is that if main breaker has 22kAIC rating then the solar breaker also should have same interrupt ratings.
I Just dont undesrtand that from where did he get that information
So whats the solution here do Eaton even make breakers that are rated 22KAIC FOR 240 VOLTS.
Click to expand...
Is the reviewer asking for the solar breaker to also have a 22kA series rating with the branch breakers like the main does?
 
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