Interrupting capacity of sub breakers

P

PCEC

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B.C. Canada eh.
I have a 400A 120/208V MLO switchboard with 18kAIC bracing. Do my breakers also need to be 18 kAIC? I assume it is 18kAIC for a reason but haven't seen a calculation and do not know the actual available short cct current.
 
Awfully low bracing for a switchboard. I would double-check.
Your branch breakers would need to be rated for the available fault current although they would likely series-rate with your main.
In any event, the available current should not exceed the bracing.
 
augie47 said:
Awfully low bracing for a switchboard. I would double-check.
Your branch breakers would need to be rated for the available fault current although they would likely series-rate with your main.
In any event, the available current should not exceed the bracing.
Click to expand...
It's a MLO switchboard so there can only be a series rating with a certain upstream fuse.
 
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