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?

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    I'm not an electrician but I am an Engineer; so I will apply the basic principal we are taught to employ as a prospective answer: Always consider (discarding schedule as moot in this case), always consider cost and technical. Cost you've got nailed down (on the surface) - the purchase is cheaper. Now ask how often you replace the "less expensive product"? Rarely if ever right? Now ask the TECHNICAL question: a residential rated breaker is in a metal box with moderate inductive loads running off of them. Surges and such should not cause injury or fire. Whats the possible advantage of heavier? – noybman Jul 25 '17 at 0:41
  • @noybman Good answer. You should add it as an answer. – ArchonOSX Jul 25 '17 at 10:05

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!

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  • I only proposed an approach to determining the answer. You asserted it. Thanks for the +1. – noybman Jul 25 '17 at 23:28

I am sure that you understand that a residential Panel is actually a Loadcenter and not an actual Panelboard. It doesn't do you any good to install high fault pass through breakers without upgrading the bussing of the equipment it's attached to. Otherwise you may save the breaker but you'll probably blow the entire Panel off the wall. Before I did any of that I would run a Fault Current Calculation to see if I really needed one.

Like you said this is for areas that have high fault current. Consider that the xfmr impedance and the aluminum utility conductors are usually downsized by the utility company and you are normally connecting to less than 400A (the largest residential meter in my area is a 320A) and most agree you don't need a calculation for single phase equipment under 400A. Because of that I would think that the available fault at your main would be less than 10 KAIC and most conductors after the Panel are so small they won't even carry 10K.

Hope this helps.

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  • Re: bussing -- quite a bit of loadcenter bussing is already rated for high fault currents (I spot checked QO bussing, and it goes up to 65kAIC, while the entire current Siemens loadcenter lineup has 100kAIC busses). – ThreePhaseEel Jul 27 '17 at 11:27

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