Yes Jim, you brought up a good point. Even the fault current from a 20 amp
circuit breaker on a hard short has enough force to make the wires slap the
inside of a conduit hard enough to be audible outside the wall they are running
in. They make a unique sound, once heard you will always know what caused it.
It's common to have more than 50k short circuit amps delivered from a larger
transformer and you have to brace buss work to handle this.
The calculations on heating of copper water pipe are good unless a arc of
plasma occurs. I think of what 50 amp, 40 volt DC or AC can do to a welding
electrode. Even without a arc it will come to red heat in a second or less.(
Have used welding machine as constant current source to melt ice in frozen
pipes too., but this is a much longer current flow and not too relevant except
to note that the resistance of the pipe is not negligible) Are underground arcs
doing damage? I don"t know.
Is the heating in a pipe, that's not flowing water, enough expansion to
raise pressure to failure point of pipe if the rise time is faster that the
pressure relief valve can react?
Does the connection of tower grounds to house grounding make this more
frequent?
Always more questions that answers.
73
Nick
WB7PEK
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