AIC and series

[titan1021]

Quick question about AIC

I am looking at a commercial project where the plans call for a 22k AIC rated panel.

I've verified with the utility that the actual rating of the AIC at the building is 18k. This project will have a sub-panel, if the main breaker at the service is rated at
22k wouldn't I be able to use 10k rated breakers downstream at the sub-panel provided the main breaker is series rated.

This is 120/240v single phase, the main breaker will be 200amps

Thanks

 

[GoldDigger]

There is no such thing as a series rated main breaker or a series rated branch or sub panel breaker.
There are only series rated combinations of specific upstream breakers with specific downstream breakers. The combinations are tested together, and it is unlikely that any manufacturer would spend the money to series rate their breakers with those of another manufacturer.

In addition, because of the complexities of dynamic impedance a series rating for breaker A with breaker B will not apply if breaker C is in between them.
For this reason there are also offiicially tested and designated three breaker series combinations, again with specific part numbers.

 

[wbdvt]

Quick question about AIC

I am looking at a commercial project where the plans call for a 22k AIC rated panel.

I've verified with the utility that the actual rating of the AIC at the building is 18k. This project will have a sub-panel, if the main breaker at the service is rated at
22k wouldn't I be able to use 10k rated breakers downstream at the sub-panel provided the main breaker is series rated.

This is 120/240v single phase, the main breaker will be 200amps

Thanks

What GoldDigger said plus let's get our terminology correct.

AIC - Ampere Interrupting Capacity- this is the fault current that an overcurrent protective device such as a breaker can safely interrupt
SCCR - Short Circuit Current Rating - this applies to equipment such as a panel and relates to the amount of fault current that it can withstand

The figure that the utility supplied you is most likely the infinite bus fault current based on the transformer kVA and impedance that supplies the service. It is not AIC. AIC and SCCR are both values that are determined by testing and marked on the equipment.

 

[electrofelon]

There is no such thing as a series rated main breaker or a series rated branch or sub panel breaker.
There are only series rated combinations of specific upstream breakers with specific downstream breakers. The combinations are tested together, and it is unlikely that any manufacturer would spend the money to series rate their breakers with those of another manufacturer.

In addition, because of the complexities of dynamic impedance a series rating for breaker A with breaker B will not apply if breaker C is in between them.
For this reason there are also offiicially tested and designated three breaker series combinations, again with specific part numbers.

Ok, but despite some terminology and phraseology nitpicks, the answer to the OP's question is yes. A 10K branch breaker will almost certainly be series rated with a 22 kaic 200A main.

One thing you might want to clarify is whether they want everything to be fully rated or are okay with usage of the series rated combinations.

 

[jim dungar]

Ok, but despite some terminology and phraseology nitpicks, the answer to the OP's question is yes. A 10K branch breaker will almost certainly be series rated with a 22 kaic 200A main.

Proper usage of terminology and phraseology is not nitpicking, it is often essential for getting a correct answer.

If the specs ask for a 22kA rated panel, then an RFI should be processed asking if series ratings are permissible.

My concern is the issue of motor loading in commercial buildings. If there is more than 100A of motor loading series ratings using 10kAIC breakers may not be possible.

 

[electrofelon]

In addition, because of the complexities of dynamic impedance a series rating for breaker A with breaker B will not apply if breaker C is in between them.

That is not necessary true. Eaton says any fully rated breaker can be used in the middle of a tested combination:

https://www.eaton.com/content/dam/eaton/products/low-voltage-power-distribution-controls-systems/panelboards/panelboard-and-switchboard-series-rating-information-manual-1c96944h02.pdf

 

[David Castor]

Many specifications, at least the ones I used to write, specifically disallow the use of series ratings and require all breakers to be fully rated. So you might want to check this.

 

[Jraef]

...A 10K branch breaker will almost certainly be series rated with a 22 kaic 200A main.

I am not as confident in that certainty, a Series Rating is ONLY available in specific tested combinations of devices. Most manufacturers will provide you with a list of their specific combinations, but you cannot take anything for granted.

 

[electrofelon]

I am not as confident in that certainty, a Series Rating is ONLY available in specific tested combinations of devices. Most manufacturers will provide you with a list of their specific combinations, but you cannot take anything for granted.

Well we could on on throwing out different adjectives and adverbs and debating if they are an appropriate verbalization..... But I stand by my statement that pretty much any non-obsolete (adding that to my post #4 statement) 200 amp 22kaic breaker will have a series rating with a standard 10K branch. For example, looking at the Siemens series rating charts, the "240 volt breaker" section is 62 pages long (granted not all of it is 250 amp or less framed devices of course). IT includes every 250/225/200 amp frame device I have ever heard of and a ton more that I have never heard of, and even goes up to a 200,000 KAIC 250A frame breaker that has a series rating with a standard 10k branch. Maybe, say, Eaton whose products I am not very familiar with has "a bunch" of 250/225/200A frame devices of which a standard 10K BR breaker doesnt have a series rating with, but I am skeptical.

 

[electrofelon]

There is no such thing as a series rated main breaker or a series rated branch or sub panel breaker.
There are only series rated combinations of specific upstream breakers with specific downstream breakers.

Proper usage of terminology and phraseology is not nitpicking, it is often essential for getting a correct answer.

Certainly using the correct terminology and definitions of SCCR vs AIC is important. I am not disputing that. That part of Goldie's post I found a little nitpicky is what I quoted above. While of course technically correct, that it doesn't matter whether a given breaker is serving as a service disconnect, a feeder or a branch circuit, it should be noted that many manufacturers use such terms in their series rating charts. For example, Siemens uses the term "main breaker" for the upstream breaker, and "branch breaker" for the downstream breaker.