AIC rating determination

[titan1021]

I'm looking at a small restaurant remodel for a client and on the plans the architect is calling for 22k AIC rating on the panel boards. This is a very old building that has been completely gutted, the original service is still there but all the labels are missing. I've done several restaurants in the same area, (its a small town) and they have all been 10k AIC. I reached out to the architect to ask how the AIC rating was determined and he just replied that, that's what the selected equipment calls for. It seems to me that there were no calculations or verifications done to determine that this high AIC rating would be required.

So my question is, is how is the AIC rating determined and by who?

I've already google this and can't seem to find the simple answer I'm looking for. Does this rating come from the utility provider?

The reason I'm trying to confirm the rating is actually warranted, is the cost and availability difference when it comes to the panels and breakers.

Thank you

 

[augie47]

The "base" (starting) number normally comes from the utility.
(You need to confirm the point of reference: ie: Transformer, end of drop/lateral, etc)

22k series rate panels are fairly common

 

[electrofelon]

The "base" (starting) number normally comes from the utility.
(You need to confirm the point of reference: ie: Transformer, end of drop/lateral, etc)

22k series rate panels are fairly common

Yeah, OP didn't give specifics about the service set up, but if you have 200 amp main breaker (s), they will almost certainly series rate with 10 k branches.

Regarding how is the AIC rating determined, you have basically three options:

1. Guess
2. Get the number from the POCO
3. Calculate it yourself using POCO transformer nameplate data (if you can see it)

 

[petersonra]

So my question is, is how is the AIC rating determined and by who?

The AIC rating required is determined by the available fault current at the panelboard.

You start with the available fault current from the POCO and calculate what it is at the panelboard. This is mostly about the resistance of the conductors to the panelboard.

In this case, it was determined by the architect. He probably knows what the POCO number is and rather than screw around trying to save a tiny amount of money on the panelboard, he just said to use 22 kAIC. Architect time is expensive, the difference between a series rated 22kAIC system and a 10 kAIC system is usually not very much, so it is not worth the time to even look at it.

 

[jim dungar]

The AIC rating required is determined by the available fault current at the panelboard.

In a perfect world maybe.
In many cases, especially for ≤200A 240V services, the required AIC comes from the utility minimum service requirements.
In other case the designer/architect simply uses a standard value from their boilerplate specs, such as 65kAIC for 480V and 22kAIC for 208V.
And of course, there is the old 'we have always done it this way' method of choosing equipment.

 

[petersonra]

In a perfect world maybe.
In many cases, especially for ≤200A 240V services, the required AIC comes from the utility minimum service requirements.

There is nothing really wrong with this approach as far as selecting AIC ratings for breakers. The cost difference between 10 kAIC and 22 kAIC series rated is so low these days that it is not worth the time spent worrying about it.

 

[brantmacga]

There is nothing really wrong with this approach as far as selecting AIC ratings for breakers. The cost difference between 10 kAIC and 22 kAIC series rated is so low these days that it is not worth the time spent worrying about it.

I have a job going right now, a 4-tenant shell, that called for 22kaic fully rated service. Ordered all the 225A panelboards and disconnects. A month in now and they’ve got the spaces leased and send the drawings over for what each tenant needs.

It was cheaper by several thousand dollars to buy new 22k fully rated panelboards with breakers than to buy loose 22k breakers. A loaded 22k panelboard was within a couple hundred dollars of an empty 22k panelboard.


Sent from my iPhone using Tapatalk

 

[electrofelon]

I have a job going right now, a 4-tenant shell, that called for 22kaic fully rated service. Ordered all the 225A panelboards and disconnects. A month in now and they’ve got the spaces leased and send the drawings over for what each tenant needs.

It was cheaper by several thousand dollars to buy new 22k fully rated panelboards with breakers than to buy loose 22k breakers. A loaded 22k panelboard was within a couple hundred dollars of an empty 22k panelboard.


Sent from my iPhone using Tapatalk

I recently got a Siemens quote and due to a misunderstanding they first quoted me 22k AIC branches, but then sent me the quote with 10 branches. IIRC it was a cost difference of $3.50 per pole - 240v bolt ons.

 

[titan1021]

Yeah, OP didn't give specifics about the service set up, but if you have 200 amp main breaker (s), they will almost certainly series rate with 10 k branches.

Regarding how is the AIC rating determined, you have basically three options:

1. Guess
2. Get the number from the POCO
3. Calculate it yourself using POCO transformer nameplate data (if you can see it)

The existing service is a 200a 120/240v service.

 

[titan1021]

I recently got a Siemens quote and due to a misunderstanding they first quoted me 22k AIC branches, but then sent me the quote with 10 branches. IIRC it was a cost difference of $3.50 per pole - 240v bolt ons.

I could see that with bolt-ons, but if I can use 10k plug-ons like BR's or QT's the cost difference is significant.