> OK. We have to consider the possible fault current during the time that
> the
> breaker takes to open (or not, sometimes!) Interestingly, there was a
> Boeing
> 747-400 had a bit of a problem 10 years ago because Boeing mistakenly
> fitted a
> 25 amp breaker instead of 2.5Amp breaker, and the wiring couldn't handle
> the
> fault current. So the fuses in out mains plugs have something like a
> 60kAmp fault breaking capability i.e. they can break a fault current of
> 60kA. They
> don't get long to do it, obviously!
>
> 73
> Peter G3RZP
>
>
> Peter in your observation above, indeed that would be a problem since the
> breaker required and the breaker installed was a factor of 10 times. Lou
Neither time, nor the circuit breaker size play a role in the available
fault current. Most common residential circuit breakers are rated for a 10K
ampere fault current, which is more than adequate for most residential
services. Most generators are capable of providing much less fault current
than that available from the utility.
Some commercial fused switches are rated to safely handle up to 200K
amperes.
Jim Smith,
KQ6UV
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