KAIC Rating from Utility Company to Panel

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Electricalhelp

Senior Member
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NJ
The following information I received from the utility company

The fault Current for this project is as follows:
Phase – Phase = 9693 Amps
X/R Ratio: 1.2

I specified the KAIC to be 10KAIC, since the rating should be higher than the available fault current.

But when I got the submittal for the EC, it specified the MDP to be 42 KAIC.

Will the system still work if the other breakers installed in the Panel are 10 KAIC.
 
After re looking at the submittal again, the MDP is rated at 42 KAIC and the subpanels are rated at 65kaic.

Will this method work downstream as well.
 
The "IC" in kAIC stands for "Interrupting Capacity", so it can only apply to devices that interrupt, like circuit breakers and fuses.

What that normally would mean then is that the PANEL is going to include a Main breaker with a 42kAIC rating. The panel itself will have BRACING for at least 42kA, but the breaker would/could have the 42kAIC rating, or higher.

That said, this appears to be the part number for a Siemens P3 panelboard with 80 pole spaces and 600A bus. The "VJ" in the middle means it has a 3VA54 Main Breaker, which alone is rated for 85kAIC. So it's likely that the 42kA rating is because the bus bracing is only 42kA, ergo the fact that the breaker is rated higher becomes irrelevant, since you cannot apply it to a system capable of more than 42kA.

All of that is irrelevant though in your case, you only have 9.693kA of available fault current. Pretty much anything you put in there is fine.
 
Jraef said:
The "IC" in kAIC stands for "Interrupting Capacity", so it can only apply to devices that interrupt, like circuit breakers and fuses.

What that normally would mean then is that the PANEL is going to include a Main breaker with a 42kAIC rating. The panel itself will have BRACING for at least 42kA, but the breaker would/could have the 42kAIC rating, or higher.

That said, this appears to be the part number for a Siemens P3 panelboard with 80 pole spaces and 600A bus. The "VJ" in the middle means it has a 3VA54 Main Breaker, which alone is rated for 85kAIC. So it's likely that the 42kA rating is because the bus bracing is only 42kA, ergo the fact that the breaker is rated higher becomes irrelevant, since you cannot apply it to a system capable of more than 42kA.

All of that is irrelevant though in your case, you only have 9.693kA of available fault current. Pretty much anything you put in there is fine.
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And one thing to remember is, many times what the manufacturer sends you for a description is not exactly what you have. They often will put what you requested. For example as you note the 3va breaker is 85k, but they still put 42k because that is what the customer needed. Siemens panelboards all have a 200k SCCR. I have also seen Siemens use odd amp ratings. One time I had a bunch of 125A P1's (project someone else started and ordered) even though they are either 250 or 400A bussing on a P1.
 
Electricalhelp said:
The following information I received from the utility company

The fault Current for this project is as follows:
Phase – Phase = 9693 Amps
X/R Ratio: 1.2

I specified the KAIC to be 10KAIC, since the rating should be higher than the available fault current.

But when I got the submittal for the EC, it specified the MDP to be 42 KAIC.

Will the system still work if the other breakers installed in the Panel are 10 KAIC.
Click to expand...
IMO, whomever specified the 42kAIC rating for the panel might not get the difference between SCCR and kAIC and how they relate to available fault current (AFC), and he wants to be conservative. Either that or he knows something that you don't about the AFC from the utility; 9692A of AFC at the secondary terminals sounds low to me for a transformer feeding a 600A service.
 
ggunn said:
IMO, whomever specified the 42kAIC rating for the panel might not get the difference between SCCR and kAIC and how they relate to available fault current (AFC), and he wants to be conservative. Either that or he knows something that you don't about the AFC from the utility; 9692A of AFC at the secondary terminals sounds low to me for a transformer feeding a 600A service.
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could be some misunderstanding of what actually goes into selection. The 42k MDP possibly is somewhat a common interrupt rating for main breaker even if actual available current is less. Might even be planning for the future should the transformer get upgraded when more load is added to a now over sized MDP?

The 65K for subpanels is probably SCCR of the bus only, chances are they have lesser AIC breakers installed. Would likely be pretty expensive and unnecessary to need that high of a rating for breakers most cases at sub panels but all the available panels in a particular product line might have that high SCCR.
 
JoeStillman said:
I noticed that the 600A frame Siemens 3VA breaker starts at 85 kAIC, so that may be why you got a submittal so much higher rated than you asked for. I don't think anybody makes a 600A breaker at 10 kAIC.
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I think you are right about that. It would be difficult to sell enough of them to make it worth having a low rated version.
 
Electricalhelp said:
The following information I received from the utility company

The fault Current for this project is as follows:
Phase – Phase = 9693 Amps
X/R Ratio: 1.2

I specified the KAIC to be 10KAIC, since the rating should be higher than the available fault current.

But when I got the submittal for the EC, it specified the MDP to be 42 KAIC.

Will the system still work if the other breakers installed in the Panel are 10 KAIC.
Click to expand...
Is this 9693A at the pri. side of the xfmr ? If it is, we need to know the transformer details (voltages, kVA, Z%, tap) and any cable info. to derive the fault current at the secondary side. We also need to know if there is considerable motor contribution to the panelboard.
 
Sometimes the information needed to calculate the AFC at a particular point is not easily gotten. My default in such cases is to set the kAIC/SCC ratings equal to or greater than the AFC at the utility transformer secondary.
 
Hi, I have a situation where the old (1988) main panel (MDP) is 600A, 3 Phase, 208V, MLO rated at 25KAIC. The feeder calculations inside MDP have breakers from 9KAIC to 25KAIC. In the new design some of the breakers are 35A, and 25A, 3 phase, 208V. However, the contractor is asking if he can use 10KAIC breakers even though the MLO MDP shows it to be rated at 25KAIC?

He does not find Cutler-Hammer 35A and 25A breakers that are 22KAIC. I did not find the Utility provided Fault Current to calculate the Short Circuit ratings for all the feeders. Please advise. Thanks
 
Samardas said:
Hi, I have a situation where the old (1988) main panel (MDP) is 600A, 3 Phase, 208V, MLO rated at 25KAIC. The feeder calculations inside MDP have breakers from 9KAIC to 25KAIC. In the new design some of the breakers are 35A, and 25A, 3 phase, 208V. However, the contractor is asking if he can use 10KAIC breakers even though the MLO MDP shows it to be rated at 25KAIC?

He does not find Cutler-Hammer 35A and 25A breakers that are 22KAIC. I did not find the Utility provided Fault Current to calculate the Short Circuit ratings for all the feeders. Please advise. Thanks
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You basically have three options:
1. Guess what the Afc is
2. Make assumptions based on what is existing and that it was done correctly and that nothing has changed
3. Figure out what the actual available fault current is and go from there.
 
engineering007 said:
9693 Amps @ What voltage? Typically, the values for the high-voltage side are provided and you have to calculate downstream
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Around here the utilities give you the available fault current at the secondary terminals of the transformer that supplies the service.
 
don_resqcapt19 said:
Around here the utilities give you the available fault current at the secondary terminals of the transformer that supplies the service.
Click to expand...
And I treat it as a minimum kAIC rating for additional components if I have no other information about the electrical system.
 
Electricalhelp said:
The following information I received from the utility company

The fault Current for this project is as follows:
Phase – Phase = 9693 Amps
X/R Ratio: 1.2

I specified the KAIC to be 10KAIC, since the rating should be higher than the available fault current.

But when I got the submittal for the EC, it specified the MDP to be 42 KAIC.

Will the system still work if the other breakers installed in the Panel are 10 KAIC.
Click to expand...
If you see this can you clarify a couple things for me. Your profile doesn't say what your position is, so when you say "I specified the KAIC..." what is your responsibility in the specifying? When you say "I got the submittal FOR the EC" did you mean from, if you got it for? I am trying to figure out why someone would decide to spend extra money on 42 and 65 KAIC breakers when (if) they don't have to.
 
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