breaker AIR rating

[zeb7k]

I understand that AIR stands for Ampere Interrupting Rating.

I'm wiring a 200A service for a residence with a Q0 load center. Where in the NEC (pun) does it show what AIR rating I should use when selecting breakers? When should I use 10,000 AIR, when should I use

22,000 AIR or higher?

--zeb

[Bud--]

NEC 110.9 requires the overcurrent devices to have an interruput rating high enough to interruupt the available fault current. Get the available fault current from the utility. It depends on supply wire size and length, transformer % impedance, fault current available to the supply transformer. For a large installation with multiple panels, the available fault current at panels is calculated by the designer, commonly an engineer. The designer also needs to know the fault current avilable from the utility. I would guess 10,000 would be high enough.

-- bud--