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Joined: Nov 2000
Posts: 246
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If you have a panelboard rated 22k AIC, and you install a breaker rated only 10k AIC, and assuming no series combo ratings, is the complete setup rated 10k or 22k?
Where is this addressed in the NEC?
Thanks
Rick Miell
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Joined: Nov 2000
Posts: 2,148
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If the available current at the line side of the breaker exceeds 10k, you can't install that breaker. See 110.9. I guess you would have to say that the set-up is only good for the 10k after you install the 10k breaker. It doesn't really change the rating of the panel or the other breakers, but prohibits the use of the panel with the 10k breaker on a system where the available fault current exceeds 10k.
Don
Don(resqcapt19)
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Joined: Aug 2001
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Don,
Would the NEC allow a breaker rated lower than the prospective fault current if there is a properly rated OCPD upstream?
We commonly use domestic breakers rated 6000A AIC here on supplies capable of delivering a much higher current. The higher AIC rating of the main cartridge fuse is considered adequate protection against a dead short.
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Joined: Nov 2000
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Paul,
If it is a listed and tested "series rated" system, a lower rated breaker may be used. This system cannot be calculated based on let through curves or any other type of calculation. It must be tested by a testing lab and listed.
Don
Don(resqcapt19)
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Joined: Aug 2001
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Ah, so only if the actual series combination is listed for such use then. Thanks.
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