coordination question

[qcroanoke]

If I have a 200 amp 240 volt 10,000 A.I.C. breaker enclosure feeding a 200 amp panel with a 200 amp main 22,000 A.I.C. and the panel contains breakers with a 10,000 A.I.C. would you be surprised if a ground fault on a 20 amp breaker tripped the main breaker in the panel as well as the 20 amp breaker?
Do I have a coordination problem?
All breakers are Square D.

 

[zog]

If I have a 200 amp 240 volt 10,000 A.I.C. breaker enclosure feeding a 200 amp panel with a 200 amp main 22,000 A.I.C. and the panel contains breakers with a 10,000 A.I.C. would you be surprised if a ground fault on a 20 amp breaker tripped the main breaker in the panel as well as the 20 amp breaker?
Do I have a coordination problem?
All breakers are Square D.

My guess is your 200A breaker has GF protection and your 20A does not.

 

[qcroanoke]

My guess is your 200A breaker has GF protection and your 20A does not.

Just the opposite. 20 amp breaker is feeding a gfi receptacle that is supplying a jacket heater on a outside Genset.

 

[jim dungar]

If I have a 200 amp 240 volt 10,000 A.I.C. breaker enclosure feeding a 200 amp panel with a 200 amp main 22,000 A.I.C. and the panel contains breakers with a 10,000 A.I.C. would you be surprised if a ground fault on a 20 amp breaker tripped the main breaker in the panel as well as the 20 amp breaker?
Do I have a coordination problem?
All breakers are Square D.

If your L-G fault was in excess of about 1100A, it is extremely possible that the 200A main could open and clear prior to the 20A device operating. Just because a device is larger does not mean it is slower.

 

[Jraef]

If I have a 200 amp 240 volt 10,000 A.I.C. breaker enclosure feeding a 200 amp panel with a 200 amp main 22,000 A.I.C. and the panel contains breakers with a 10,000 A.I.C. would you be surprised if a ground fault on a 20 amp breaker tripped the main breaker in the panel as well as the 20 amp breaker?
Do I have a coordination problem?All breakers are Square D.

You MIGHT have a coordination problem, but it depends.
1) If your Available Fault Current is between 10kA and 22kA, then the first panel is illegal.
2) If your AFC is below 10kA, someone wasted money on panel #2 but that is not illegal.

In either case it will not make any difference whatsoever in the tripping coordination of the mains on those panels, they would be the same. AIC ratings have nothing to to with trip coordination in all but certain special cases*. So what Jim Dungar said is much more likely. And by the way, I would highly suspect that the GF happened BETWEEN the 20A CB and the GFCI receptacle because if it happened down stream of the GFCI receptacle I would expect that would trip faster than either breaker. Not guaranteed, but much more likely.

* Sometimes when you get into larger systems with series rated devices a difference in a device used in series may end up being a different trip curve. But I would be highly surprised if a 200A MCB on a 10kA panel and the same one on a 22kA panel have different trip curves. In fact more than likely they are the exact same breaker with a different sticker on it (and a higher price for the priviledge).

 

[qcroanoke]

Thanks for the insight!
Upon futher review... Customer now says 20 amp breakers did not trip. 60 amp breaker feeding a Transtector surge suppressor did! Along with the main. Also mentioned when it happened it was a weather event both times.
They did not seem to want to talk about the weather playing into this though.
AIC was mentioned because of the different ratings on the main breakers but I told them I could hardly see that having much to do with it. AIC rating was only what it would withstand and that the trip curves were the same no matter the AIC rating.
I think the biggest concern is that the main tripped behind the ATS and the ATS did not see a power failure and the building went down because of it.
It is not our design. but I do see where this is going to become a point of discussion because the panel should really be a main lug since there is a main breaker in front of the ATS.