So what does an AIC / AFC failure look like in the field ? 10k breaker on 18k AFC drop.

Merry Christmas
jim dungar said:
Residential style breaker AIC values have been available since at least the 50's. Back then 5kA was standard. UL raised the minimum to 10kA some time in the 60s.
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Sure, but they were absolutely not printed on the breakers which is the field check issue.

And series ratings require a set of circumstances that's no so helpful in my area of mostly 1920-1970's buildings.
A fused 200-400 amp main combined with individual 10k circuit breakers is the most common setup, fed by AIC ratings of the 18k to 45k range from the power company. That holds for single family homes and apartment.

The original question was has anyone seen a breaker blow up due to the AIC issue?
Is this an identified hazard that should concern me, or an edge case?
 
jim dungar said:
If the breaker does not say otherwise, the default would be 5kAIC, as this is the lowest they ever made.
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If that's the value, then every apartment building in the area is out of compliance.
The typical setup is 100 amp to 400 amp fuses in a disconnect box,
a hot gutter to individual meter sockets, then per-unit mains with either 30-60 amp fuses, or the equivalent breaker.
Most of those breakers are unlabeled, but if they are 10k breakers or 10k quads.
 
brycenesbitt said:
fed by AIC ratings of the 18k to 45k range from the power company. That holds for single family homes and apartment.
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But after the service drop (usually small conductors), and the service entrance conductors, what do you really have available at the line side of the main?
 
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