Current production residential/light commercial breaker lines are available in multiple interrupting capacity ratings — this rating is how much current the breaker can safely interrupt without blowing itself to bits from the effects of the arc inside. For instance, the Siemens breakers come in 10kA, 22kA, and 65kA, while Eaton BRs come in 10kA, 22kA, and 42kA with a few available in 65kA as well.
This is useful in commercial work, where larger services and feeders can deliver higher fault currents than the 10kA typically standard for residential and light commercial services. However, would installing more robust (i.e. higher interrupting rating) breakers deliver an advantage in longevity even if a 10kA breaker could handle the maximum prospective fault currents available from the service? Or should I simply get 10kAIC branch breakers as the higher ratings are more cost without any benefit if you don't need them?
Best Answer
The interrupt current rating is only for the purpose of a high current fault like a ground fault or short circuit. (This is also sometimes referred to as a withstand current.) As long as the breaker can interrupt the fault safely it can be used in that application.
This is nothing you didn't already know.
The robustness of the product for a higher interrupt rating will not add any value in a lower rated installation. Since a residential installation will never exceed 10,000 amps short circuit current there is no need for a higher rating.
The higher cost of a higher rated breaker has no payoff in a lower rated system since it will never be realized in the lifetime of the product. If the product reaches its end of life without ever having used the extra robustness, where is the added value?
I had my well driller tell me to use #12 wire and a 20 amp circuit to feed the well pump when the manual specified a 15 amp circuit with #14 wire. His justification was "bigger is always better". That is unless you are the one paying for it. I elected for the smaller circuit. The extra cost is wasted since it is never used.
I am an overbuilder myself but I try to resist the temptation to spend money on things that will never pay off.
Good luck!